Data Sheet

Freescale Semiconductor
Data Sheet: Product Preview
Document Number: CRTOUCHDS
Rev. 3, 04/2013
CRTouch
CRTouch Data Sheet
Capacitive and Resistive Touch
Sensing Application Specific IC.
The CRTouch is a Ready Play solution device designed to serve as a four wire and five wire resistive touch driver and a
capacitive touch sensing device in a single 32-pin QFN package. It provides all the signal interfacing and processing to calculate
X and Y coordinates as well as to detect and process two touch gestures for human-machine interface applications. It’s key
features are:
Features
•
•
•
•
•
•
•
•
•
•
•
X and Y coordinates calculated from a resistive touch screen with built-in filter to improve stability
Slide gesture detection for single touch.
Two touch gesture detection for resistive four wire screens
— Zoom In and Zoom Out
— Rotate with clockwise and counter clockwise indication.
Four capacitive keys in different configurations
— Rotary
— Slider
— Keypad
UART communication and I2C communication available
Baud-rate auto detection pin to enable automatic synchronization with any UART baud-rate between 9600 and
115200 bps using the same UART RX pin
Configurable scanning period that can calculate up to 200 coordinate points per second
1.8 to 3.6 volts operation
32-pin QFN package
–40 °C to 105 °C operating temperature
Normal Run mode, Sleep mode, and Shutdown mode for lower power consumption operation
This document contains information on a product under development. Freescale reserves the
right to change or discontinue this product without notice.
© Freescale Semiconductor, Inc., 2007-2012. All rights reserved.
Table of Contents
1
2
Pins and Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.1 Device block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.2 Device pin out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.3 Recommended system connections . . . . . . . . . . . . . . . .5
1.4 Signals description . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.1 CRTouch resistive touchscreen scanning . . . . . . . . . . . .7
2.1.1 Touchscreen electrical signals . . . . . . . . . . . . . . .7
2.1.2 CRTouch scanning process . . . . . . . . . . . . . . . . .8
2.1.3 Resistive events. . . . . . . . . . . . . . . . . . . . . . . . .10
2.1.4 Calibration process . . . . . . . . . . . . . . . . . . . . . .10
2.1.5 Data FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.1.6 Resistive gestures . . . . . . . . . . . . . . . . . . . . . . .15
2.2 Capacitive subsystem . . . . . . . . . . . . . . . . . . . . . . . . . .17
2.2.1 Capacitive touch detection. . . . . . . . . . . . . . . . .17
2.2.2 Keypad control . . . . . . . . . . . . . . . . . . . . . . . . . .18
2.2.3 Rotary and slider control . . . . . . . . . . . . . . . . . .18
2.3 Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.3.1 Run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.3.2 Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.3.3 Shutdown mode. . . . . . . . . . . . . . . . . . . . . . . . .20
2.4 Internal voltage regulator . . . . . . . . . . . . . . . . . . . . . . .21
2.4.1 Internal voltage regulator features . . . . . . . . . . .21
2.4.2 Internal voltage regulator modes of operation . .21
3
Serial Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 I2C interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 I2C bit transfer . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2 I2C START and STOP conditions. . . . . . . . . . .
3.1.3 I2C transferring data. . . . . . . . . . . . . . . . . . . . .
3.1.4 I2C acknowledge . . . . . . . . . . . . . . . . . . . . . . .
3.1.5 CRTouch I2C slave address . . . . . . . . . . . . . . .
3.1.6 Message format for Writing CRTouch . . . . . . .
3.2 UART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1 UART Baudrate auto detection. . . . . . . . . . . . .
3.2.2 UART communication protocol. . . . . . . . . . . . .
3.2.3 Registers Read through UART. . . . . . . . . . . . .
3.2.4 Registers Write through UART . . . . . . . . . . . . .
4 Memory Map and Registers Description . . . . . . . . . . . . . . . .
4.1 Device memory map . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Registers description . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.1 Resistive Touch Status registers . . . . . . . . . . .
4.2.2 Capacitive Touch Sensing Status registers . . .
4.2.3 Resistive Touch Configuration registers . . . . . .
4.2.4 Calibration Values registers . . . . . . . . . . . . . . .
4.2.5 TSS Configuration registers . . . . . . . . . . . . . . .
Appendix AElectrical Specifications. . . . . . . . . . . . . . . . . . . . . . .
Appendix BPacking Information. . . . . . . . . . . . . . . . . . . . . . . . . .
22
22
23
23
24
24
24
25
25
25
26
26
27
28
28
34
34
41
44
50
51
59
62
CRTouch Data Sheet, Rev. 3
2
Freescale Semiconductor
Pins and Connections
1
Pins and Connections
1.1
Device block diagram
Figure 1. Block diagram
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
3
Pins and Connections
1.2
Device pin out
Figure 2. Device pinout
CRTouch Data Sheet, Rev. 3
4
Freescale Semiconductor
Pins and Connections
1.3
Recommended system connections
Figure 3. Recommended system connections
NOTE
1.
2.
3.
4.
Resistive touch screen signals are bi-directional only for four-wire screens. For five-wire 5WS is input and the other
four signals are outputs.
COMMSEL is connected to ground only if UART communication is desired. Otherwise it can be left unconnected.
I2C and UART communications are mutually exclusive. Only one can work during the device run time. The other pins
from the other communication protocol can be un-connected.
All unused pins can be left as Not Connected. Connecting them to ground may increase power consumption.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
5
Pins and Connections
1.4
Signals description
Table 1. Signal descriptions
Pin
Function used
for CRTouch
Description
1
Yr
Y voltage reference
2
TouchPending
Indicates that there is a previous touch event (resistive or capacitive)
fwhere data registers have not been read
3
5WUR
5-Wire Upper Right Connection
4
Y+ / 5WLR
4-Wire Y+ or 5-Wire Lower Right connection
5
X+ / 5WS
4-Wire X+ or 5-Wire Sense connection
6
Y– / 5WUL
4-Wire Y– or 5-Wire Upper Left connection
7
VDDA
VDD Signal for the ADC
8
VSSA
VSS Signal for the ADC
9-11
NC
No Connect
12
VREG_IN
Voltage regulator Input
13
V33_OUT
Voltage regulator output –3.3 Volts
14
VSS
VSS – Connect to Digital Ground
15
X– / 5WLL
4-Wire X– or 5-Wire Lower Left connection
16
Electrode1
Capacitive Touch Sensing Key #1
17
Xr
X voltage reference
18
Electrode2
Capacitive Touch Sensing Key #2
19
Electrode3
Capacitive Touch Sensing Key #3
20
Electrode4
Capacitive Touch Sensing Key #4
21
NC
No Connect
22
Baudrate Auto
Detect
Signal used to enable Baud Rate auto detection
23
I2CAddrSel
I2C Address Selection pin is used as bit 1 of the I2C address
24
VDD
VDD – Connect to system regulated power supply
25
VSS
VSS – Connect to digital Ground
26
I2C1_SDA
I2C – Bidirectional SDA communication signal
27
I2C1_SCL
I2C – Clock signal. Must be driven by the bus master
28
Reset
Reset signal
29
Com Select
Communication Select Pin. 0 = UART. 1 = I2C
30
Wakeup
Signal used to wake the CRTouch when configured to go into Sleep
or Shutdown modes. While in Sleep mode, this pin should be held
down with a logical 0 to communicate with the device.
31
UART_RX
UART Reception pin
32
UART_TX
UART Transmission pin
CRTouch Data Sheet, Rev. 3
6
Freescale Semiconductor
Functional Description
2
Functional Description
The capacitive and resistive touch (CRTouch) is a device capable of interfacing with 4-wire and 5-wire resistive touch screens.
It is capable of detecting single touch slide and two-touch rotate and pinch gestures. CRTouch includes a calibration procedure
to increase the touch detection accuracy and configurable low power and shutdown modes to reduce power consumption.
2.1
2.1.1
CRTouch resistive touchscreen scanning
Touchscreen electrical signals
The types of resistive touchscreen supported by this device are passive elements composed of two layers of conductive material
uniformly distributed across the screen . Due to the resistivity of the conductive material, it can be seen as a resistor between
the terminals of each layer. The following figure shows the construction of the 4 and 5 wire types of screens, and their simplified
electrical equivalent circuit.
Figure 4. Construction and electrical equivalent of a four wire touchscreen
Figure 5. Construction and electrical equivalent of a five wire touchscreen
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
7
Functional Description
When a voltage is applied at the terminals of one layer, the voltage is linearly distributed across the conductive material. For a
four wire screen, the coordinates of the point of contact can be determined by applying voltage to one layer and reading the
voltage on the other. For a five wire screen, one layer is used only for reading the voltage, while the other has voltages applied
in different combinations for determining the value of each axis. The following table shows how the signals are activated for X
and Y measurements in each type of screen.
Table 2. Signal states for a four wire screen
Measurement
X+
X–
Y+
Y-
X
Vdd
Vss
Z
Z
Y
z
Z
Vdd
Vss
Table 3. Signal states for a five wire screen
Measurement
UR
UL
LR
LL
X
Vdd
Vss
Vdd
Vss
Y
Vdd
Vdd
Vss
Vss
Considering these scanning sequences, the screen’s origin (coordinate 0,0) is located in the intersection of the X– and Y–
terminals for a four wires screen, and at the LL terminal for a five wire screen. It is also important to consider that the connection
between the conductive material of the screen and the terminals of the CRTouch controller represent a series resistance with the
screen. Because of this, the coordinates obtained at the edges of the active region of the screen may be a number of counts above
0 and a number of counts below the maximum value. This variation is given by the construction of the touchscreen, the
impedance of its connection lines, the size of the active area, and so on.
Another electrical phenomenon that needs to be considered is the capacitances created in the screen. Because the active area is
composed of two plates of conductive material, this creates a set of capacitances between the two layers. When combined with
the resistors created in the screen, these form an RC circuit with an associated stabilization time constant. If the voltage of one
layer is read before it stabilizes, then a deviation from the real coordinate is produced. In some devices ESD diodes may be
connected to the resistive panel for improved electrostatic immunity. In this case, low capacitance ESD diodes must be used to
avoid increasing the resulting capacitance.
2.1.2
CRTouch scanning process
The CRTouch has three scanning modes for the resistive screen. One is active when only X and Y coordinate values are desired,
the second activates when the pressure measurement is enabled, and the last one when any of the two touch gestures are enabled.
Before each sample is taken, the CRTouch waits for a configurable amount of time for the signals to stabilize. The following
figure shows the differences in the scanning process for each scanning mode.
CRTouch Data Sheet, Rev. 3
8
Freescale Semiconductor
Functional Description
X stabilization Y stabilization
X
Y
X
Sampling period
Scanning Process for X and Y coordinates only
X stabilization Y stabilization
X
Z stabilization
Y1 Y2
Z1 Z2
X
Sampling period
Scanning Process for X ,Y, and Pressure
X stabilization Y stabilization
X
Z stabilization
Y1 Y2
X stabilization Y stabilization
Z1 Z2
Xr
Yr
X
Sampling period
Figure 6. Scanning process for X, Y, pressure, and two touch gestures
As seen in the previous figure, the scanning sequence repeats at a fixed period of time. This period is configurable in the
Sampling Time register and may be in the range of 5 ms to 100 ms. The CRTouch scans the screen signals only when a touch
is detected. When the screen is not touched, the device stays in a standby state.
At the end of the scanning process, a set of coordinates is produced. These coordinates have a default resolution of 12 bits, or
4096 points per axis. However, this resolution may be modified to reflect the proportions of the screen more accurately (typical
screens have a 4:3 or 16:9 proportion). This can be done by writing to the horizontal resolution and vertical resolution, which
correspond to the X and Y resolution respectively. The resulting X and Y values are scaled to fit into this resolution.
The CRTouch is capable of autodetecting the type of the screen connected. The type of screen detected is reflected in the Status
Register 2. Only two touch gestures and pressure detection is available for 4 wire screens, and cannot be enabled when a 5 wire
screen is connected.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
9
Functional Description
2.1.3
Resistive events
The CRTouch has a TouchPending signal that can assert on configurable events in the system to alert the host of a new event
that requires attention. This signal can be used by the host to avoid time based polling of the status of the device and therefore
unnecessary use of the communication bus. Whenever an event is detected in the system, it will be reflected in its associated bit
in Status Register 1. All event bits of this register remain latched and are cleared until the register is read. This avoids losing
any detected event if the host cannot read the status of the device for several sampling periods. Each event can also be enabled
to assert the TouchPending signal through the Triggers Enable register. By setting the bits in this register, when an event is
recorded in the status register the TouchPending signal is asserted, and remains asserted until the status is read.
The most basic events that are related to the touchscreen are the resistive new sample and the touchscreen release events. The
resistive new sample is triggererd when a new sample of the screen coordinates is available, which means that it is produced at
the touch detection and subsequently at every scan period. The release event is produced only when the screen transitions from
touched to not touched. In this case the last valid coordinates value remains in the Coordinate registers.
Additional to the events status, the Status Register 1 reflects the state of the screen through its most significant bits, screen
touched and two touch bits. These bits are updated with each sampling period and unlike the events bits, they are not latched
and are not cleared with a register read, so their value always reflects the state of the screen at the last scanning sequence.
When the screen transitions to the touched state, the Resistive Touch Screen Touched and the Resistive New Sample Event bits
in the Resistive Touch Status Register 1 are set. With every new coordinate sample, the Resistive Touch Screen Touched and
the Resistive New Sample Event bits will be set after the coordinate values are available in the X and Y coordinates registers.
When the screen is released, the Resistive New Sample Event bit will be set, indicating the end of the scanning sequence, but
the Resistive Touch Screen Touched bit will now be cleared, reflecting the released state of the screen. After this condition is
met, no more touchscreen events will be reported in the status register or the TouchPending pin until a new touch is detected in
the screen.
The TouchPending signal is active low and is capable of driving an LED if user feedback is desired.
2.1.4
Calibration process
The resistive touch screen should be calibrated to get an accurate performance. This inlcudes X and Y coordinate and gesture
detection. The calibration process consists of a series of points touched by the user to give the device references on the screen
orientation, offsets, and linearity. Two different processes may be executed: one, for only single touch calibration, the other for
single and two touch calibration. In both cases, three different points need to be touched for single touch calibration. It is
recommended that these points be touched with a stylus to increase the precision achieved. In the case of two touch calibration,
two pairs of points need to be touched. As expected the two touch gestures are performed with fingers, these pairs of points
must also be pressed with fingers.
The three single touch calibration points are the following: The first coordinate should be at 10% of X and 10% of Y axis. The
second coordinate should be at 50% of X and 90% of Y axis. The third coordinate should be at 90% of X and 50% of Y axis.
The two pairs of two touch coordinates are the following and may be pressed in any order: The first pair is at 50% on the X axis
and 10% and 90% on Y axis; the second pair is 50% on Y axis and 10% and 90% on X axis.
These percentages correspond to the graphic display screen resolution. The Horizontal Display Resolution and Vertical Display
Resolution must be configured with the corresponding display resolution before executing the calibration process. Note that
both registers must be written for their new values to take effect. When the CRTouch is calibrated with the correct resolution,
the X and Y coordinates calculated by the device directly correspond to the display pixels and need no additional processing by
the graphics controller. Usually the user application displays an image showing the calibration points one at a time that must be
touched to calibrate the screen.
For increased precision, the CRTouch performs a validation of the touched points during calibration to determine if the values
are within the expected range. When the validation is not positive, a calibration error is signaled in the Status Error register. This
validation mechanism does not prevent the device from being calibrated. It serves as information to the host processor to
determine if the calibration was executed correctly. Other methods of validation can be to display an additional point in the
display and verify that the coordinate reported by the CRTouch corresponds to the displayed point. The built-in validation
mechanism is accurate only within a 5° diphase between the display and the touch panels.
CRTouch Data Sheet, Rev. 3
10
Freescale Semiconductor
Functional Description
Figure 7. Touch points for single touch calibration
Figure 8. Touch pairs for two touch calibration
The calibration process is initiated by setting bit6 into the Trigger Events register. For two touch calibration at least one of the
two touch gestures must be enabled prior to starting the calibration process. It is also important to properly configure the
resolution values to match the screen ratio, to increase the precision of the gestures detection especially for the rotate gesture.
The following diagrams show the sequence of actions followed after setting the calibration bit to start the process.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
11
Functional Description
Figure 9. Single touch calibration sequence
CRTouch Data Sheet, Rev. 3
12
Freescale Semiconductor
Functional Description
Figure 10. Single and two touch calibration sequence
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
13
Functional Description
During calibration, the touch screen scan period is fixed at 10 ms, regardless of the value configured in the Sampling Rate
register. For each point, 128 samples are taken, so each point should be held at least for 1.3 s for proper calibration.
The calibration processed may be stopped at anytime by clearing bit6 on the Trigger Events register. Asampling period must
pass before enabling it again for a new calibration process. To discard an established calibration both of the display resolution
registers must be written. It is also possible to calibrate the CRTouch device through the Calibration Values set of registers
without any touches required by the user. This is particularly useful for factory calibration to reduce the time required for this
process. In this case, a system must be manually calibrated to generate the calibration values that can be reproduced to other
devices. It is important to consider that the precision achieved by this method depends on the repeatability of the touch sensor
impedances by the manufacturer. After writing the values to these registers the CRTouch must be reset for the calibration to take
effect.
2.1.5
Data FIFO
The device has three FIFO buffers, one for X coordinates, one for Y coordinates, and one for Pressure values. Each FIFO buffer
stores up to16 samples and new samples can not be stored once the FIFO buffer is full. Each point touched on the screen yields
one X coordinate and one Y coordinate which are store onto its respective FIFO buffer. If pressure is enabled on the device,
then each point yields also a pressure value that is stored onto its respective FIFO buffer.
The three FIFO buffers are synchronized and should be read in sequence. The device has a mechanism avoiding that just one
FIFO buffer is read. If there are samples on the FIFO buffers and just one of them is read several times the device will report
the same value until the other FIFO buffers is read. This means if the pressure is enabled the X FIFO buffer, Y FIFO buffer,
and Pressure FIFO buffer should be read once before trying to read any of them again. If Pressure is disabled then only X FIFO
buffer and Y FIFO buffer should be read.
Setting the RTFIFOEN bit into the FIFO Setup register enables the FIFO buffers. Clearing this bit disables the FIFO buffers.
X, Y, and Pressure FIFO buffers are flushed each time the FIFO Setup register is written. The device returns the value 0xFFFF
if the FIFO buffers are disabled or empty.
If the FIFO buffers are enabled a watermark can be configured to generate an event once the number of samples stored onto the
FIFO buffers are bigger or equal than the watermark. The watermark is disabled by setting a zero value.
Figure 11. FIFO Watermark example
CRTouch Data Sheet, Rev. 3
14
Freescale Semiconductor
Functional Description
2.1.6
Resistive gestures
The CRTouch controller has built-in gestures detection capabilities with unique support for zoom and rotate multi-touch
gestures, as well as single touch slides. This feature offloads the host processor of continuous coordinate reading and processing
for gesture detection.
2.1.6.1
Slide
A slide is detected for linear motion in any region of the screen in a direction parallel to any axis of the screen. This means that
any motion that varies only one axis can be detected as a slide. The detection algorithm supports a deviation of 7.5° from the
axis direction to still consider the motion as a slide. The following figure shows the valid ranges for a slide motion.
Figure 12. Slide valid regions
The slide gesture is enabled through the slide enable bit in the Configuration Register, and it is reported through the Slide Event
bit in the Status Register 1. A slide can be performed in four different directions: horizontal or vertical, positive or negative in
each case. The direction of the gesture is reported in the Status Register 2 through the Slide Direction [1:0] bits. The following
table shows the reported value for each case.
Table 4. Slide gesture directions
Motion
Direction
Slide Direction [1:0]
X0 < X1, Y0 = Y1
Horizontal positive
00
X0 > X1, Y0 = Y1
Horizontal negative
01
Y0 < Y1, X0 = X1
Vertical positive
10
Y0 > Y1, X0 = X1
Vertical negative
11
The slide gesture is reported when the motion distance is higher than a configurable threshold. This threshold is a portion of the
screen resolution across each axis. For a vertical slide, a portion of the Y resolution is the threshold and for a horizontal slide,
a portion of the X resolution is the threshold. This portion is defined by the Slide Steps register value. For a value of ten, the
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
15
Functional Description
threshold is set to one tenth of the resolution; a value of one would mean one unit of the resolution, which cannot produce a
slide because no motion may have a distance greater than the resolution.
The Slide Displacement register reports the accumulated steps of the motion after it begins, therefore each time the threshold is
crossed, this value is incremented. This value is reset if a change of direction is detected or when the screen is touched after a
release.
2.1.6.2
Two touch gestures
The CRTouch device is capable of detecting when two independent touches are present in the screen and when Zoom and Rotate
gestures are performed by these two touches. Two touch detection is enabled when either Zoom or Rotate are enabled in the
Configuration register. When two touches are detected, the Two Touch bit in the Status register 1 is set. In this state, coordinates
reported in the X and Y registers should be disregarded by the display controller. When detecting a two touch event, the
CRTouch continuously measures displacement of the fingers. This displacement may reflect in terms of the distance between
the fingers (Zoom gesture), the slope of the line between the fingers (Rotate gesture), or both.
For two touch gestures to operate, it is mandatory to run the calibration process described in section Section 2.1.4, “Calibration
process.” Two touch gestures and display resolution must be configured before running the calibration to properly calibrate the
gesture detection. For two touch gestures, the CRTouch uses internally a different resolution for the distances between the
fingers in each axis. The smaller axis has a fixed resolution of 1000, while the other axis resolution is calculated to match the
screen proportions. For a screen with 16:9 proportions, for example, one axis would have a resolution of 1000 and the other of
1777. The screen proportion is calculated according to the Vertical Resolution and Horizontal Resolution values. These values
are used to calculate the distance between the fingers.
TwoTouchResolutionA = 1000
Eqn. 1
HorizontalResolution
TwoTouchResolutionB = 1000  ---------------------------------------------------------VerticalResolution
Eqn. 2
VerticalResolution
TwoTouchResolutionB = 1000  ---------------------------------------------------------HorizontalResolution
Eqn. 3
or
Whichever is the highest.
MaxTwoTouchDis tan ce =
ResolutionA  2 +  ResolutionB 
2
Eqn. 4
The signals required for two touch detection are obtained through the resistors connected to the Xr and Yr signal. Unexpected
behaviors may be produced if these resistors are not connected and two touch gestures are enabled.
2.1.6.3
Zoom gesture
When the distance between the fingers varies, a zoom gesture is detected. If the distance increases, a zoom-in direction is
reported through the RTSZD bit in the Status Register 2. If the distance decreases, a zoom-out direction is reported through the
RTSZD bit in the Status Register 2. In either case, the RTSZ bit is set in Status Register 1. Similar to the slide gesture, the zoom
gesture is reported when a threshold is crossed. This threshold is approximately one tenth of the smaller axis of the screen. The
Zoom Size register is updated each time the threshold is crossed and is cumulative throughout the gesture. The value of this
register is equal to one tenth of the distance displacement.
InitDis tan ce – ActualDis tan ce
ZoomSize = ----------------------------------------------------------------------------------10
Eqn. 5
CRTouch Data Sheet, Rev. 3
16
Freescale Semiconductor
Functional Description
The maximum distance reported in the Zoom Size register can vary this depends on the proportions of the screen.
2.1.6.4
Rotate gesture
The rotate gesture is reported when a variation of the slope between the fingers is detected. This variation must be at least 10°
for it to be reported in the RTSR of the Status Register 1. The direction of the rotate gesture is reported in the RTSRD in the
Status Register 2. The Rotate Angle register reflects the cumulative angle that has been displaced in that direction. This angle
is reported in radians with 5 fractional bits and 3 integer bits. This determines a limit of 456° of continuous rotation that can be
reported by the CRTouch. The following equation can be used to convert the value of the Rotate Angle register to a value in
degrees.
 RotateAngle  180
 = -------------------------------------------------32
2.2
Eqn. 6
Capacitive subsystem
The CRTouch controller supports up to four capacitive electrodes as an extended interface. These electrodes may be detected
independently or they can be arranged in a keypad, rotary or slider control configuration. The capacitive subsystem is enabled
through the Configuration register with the Capacitive Control [1:0] bits according to table 4. Additionally, each of the
electrodes of the CRTouch controller may be individually enabled or disabled in the Electrode Enablers register.
Table 5. Capacitive control configuration bits
Capacitive Control [1:0]
Configuration
00
Capacitive subsystem disabled
01
Rotary control enabled
10
Slider control enabled
11
Keypad control enabled
When enabled, the capacitive electrodes are scanned sequentially, from E0 to E3, at a fixed rate of 7 ms. The capacitive
subsystem of the CRTouch controller has a set of configuration and status registers to control several features.
NOTE
Before the desired control is enabled through the Configuration Register, the desired events
to be detected must be enabled in the Capacitive register; otherwise the control will not be
enabled.
2.2.1
Capacitive touch detection
The touch detection is based on a baseline tracking algorithm and thresholds for touch detection. When the system is enabled,
an initial baseline is calculated and continuous baseline recalibration can be enabled through the DCTracker feature with the
DC tracker enable bit in the capacitive system configuration. This recalibration is executed at a fixed number of scanning
periods, determined by the DC Tracker Rate register value. Since the scanning period is fixed at 7 ms, the recalibration period
is equal to the DC Tracker Rate register value multiplied by 7 ms.
To detect a touch, the capacitance samples taken for each electrode are compared against the baseline. If a number of
consecutive samples exceed a certain threshold then that electrode is considered and reported as touched. These thresholds are
defined by the Ex Sensitivity registers and represent the minimum difference that must exist between a capacitive sample and
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
17
Functional Description
the signal baseline for a touch to be detected. To avoid false touch detection due to sporadic noise, the Response Time register
defines how many samples the algorithm will consider to determine a touch or a no touch condition.
After an electrode has been detected as touched, recalibration is not performed for that electrode to avoid recalibrating the
baseline at a non-idle signal level. However, under certain environmental conditions, large and sudden changes in the measured
capacitance may occur which may trigger a touch detection. If this condition persists (excessive humidity over an electrode, for
example), the affected electrode will not be able to detect real touches. For this kind of scenario, the stuck key feature allows
the host to define a touch timeout,after which the touched status is released and the electrode is recalibrated.
The actual status of each individual electrode may be read at the Electrode Status register. Each bit represents the status of one
electrode, reporting a 1 when the electrode is detected as touched and a 0 when the electrode is not touched.
For application customization of these parameters, the CRTouch controller provides a set of registers that allow the analysis of
the capacitance behavior of each electrode under the specific application conditions. The Electrode Baseline registers and
Electrode Instant Delta registers provide this information.
The resolution of the capacitive samples and the calculated baselines can be modified through the Capacitive Resolution
registers. Increasing or decreasing the resolution is useful depending on the thickness of the dielectric used. This allows to
modify the signal (touch) to noise ratio for more flexibility on the touch detection. This value is only effective after a reset, a
reset is then needed to make a change in this register to take effect.
2.2.2
Keypad control
The keypad control supports the reporting of touch or release events for each individual electrode. These events are reported
through an events buffer and each of them is enabled through the Events register. The events buffer is mapped to the Electrodes
FIFO register of the device. Each read of this register returns the oldest previously stored in the buffer, until the buffer is empty
and any subsequent read returns a value of 0xFF. The format of the events in the buffer may be consulted in the registers section
of this document.
Additionally to the touch detection, the keypad control provides an autorepeat feature, to log new touch events into the buffer
at a certain rate after detecting the electrode as touched for a period of time. The Auto-repeat Start register controls the timeout
before it starts logging new events, and the Auto-repeat Rate register controls how often a new event is stored in the buffer.
The keypad control also provides the capability of restricting the number of keys that may be pressed at the same time. This is
done by writing a value different than 0 in the Max Touches register. When the number of simultaneous touches is equal to the
Max Touches register, no new touch events for additional keys are stored in the events buffer until one or more keys are released.
2.2.3
Rotary and slider control
The slider and rotary control types provide support for linear or circular arrangements of electrodes. A rotary may be seen as a
circular slider, where the first and last electrodes are adjacent. In the case of a rotary a simultaneous touch of these two electrodes
is considered valid, where in a slider it is not. This is the only difference between these two types of controls, otherwise all of
their behavior is the same.
Slider and rotary controls are oriented to the detection of motion through the control, so they provide the capability to detect
this motion, report its direction, and the amount of displacement. The control is also capable of reporting when the initial touch
is detected, when the motion ends and when all of the control’s electrodes have been released. All these events are enabled
through the Events register.
Two status registers are provided for these controls, the Static Status register and the Dynamic Status register. The Dynamic
Status register reports if movement is being detected at the moment through the Movement Flag, reports the direction of this
movement in the Direction bit and how many positions were advanced since the last status. The static status reports if the control
is currently touched through the touch flag, the position of the touch, and if an invalid position is detected.
To increase the number of positions detectable in a rotary or slider control, positions “between” the electrodes are also reported.
This means that when two electrodes are touched, the control reports a position different than the position of each of the touched
CRTouch Data Sheet, Rev. 3
18
Freescale Semiconductor
Functional Description
electrodes. For example, E0 corresponds to position 0, E0 and E1 correspond to position 1, and E1 corresponds to position 2.
When more than two electrodes are touched, the central position is reported.
2.3
Modes of operation
The CRTouch operating modes are described in this section. Entry into each mode and exit from each mode as well as the
function while in each of the modes are described.
2.3.1
Run mode
This is the normal operating mode for CRTouch which is the default mode for a new device. In this mode the device is not
entering into low-power nor shutdown modes at any time. Serial communications are active all the time waiting for a command
to be received. Scanning of a resistive touchscreen panel will be performed periodically as defined in the Sampling Rate register.
During run mode, all the internal circuitry remains enabled all the time. All the functions do not have any constraints or special
considerations to be used while in this mode. Power consumption is higher than in any other operating mode.
2.3.2
Sleep mode
Sleep mode is enabled through the SLEEPEN bit in the Configuration Register. This mode sends the part into a low power mode
between scanning periods of a resistive touchscreen panel. When the part is in sleep mode it turns off the internal clocks for the
serial communication peripherals, both UART and I2C. The overall function of the device is the same compared to normal run
mode, with the exception of communication interfaces.
2.3.2.1
CRTouch function in sleep mode
When Sleep mode is enabled, the part will remain in this state until the timeout configured in the Sampling rate register expires.
After the Sampling Rate period expires, the part will start the sequence to scan if the resistive touch screen connected has a new
coordinate and calculate the X and Y coordinates and gestures detection if needed.
Besides a sampling rate period expiration, there are two additional ways to transition from Sleep mode into Run mode:
•
•
Wakeup pin—The active low wakeup pin will transition the part from Sleep mode into run mode. While being asserted,
the device will remain in run mode. The part will return into Sleep mode after the signal has been de-asserted, unless
there is an active communication (UART or I2C) or the part is actively scanning a resistive touchscreen panel. For the
communication case, the communication timeout rules will apply before going back to Sleep mode. When the part is
scanning the resistive touchscreen panel, it will go back to sleep mode as soon as the scanning process finishes.
Serial communication—Either UART or I2C can transition the part from sleep mode into run mode. Each
communication interface has specific characteristics and rules while working in sleep mode.
2.3.2.2
I2C communication in sleep mode
If I2C communication is selected for CRTouch communication, a start condition followed by a Slave Address match can be
used to wakeup the part from sleep mode and transition to normal run mode. Because the I2C internal clock was turned off until
the slave address matched, CRTouch answers with a Not Acknowledge to this initial request. There are two alternatives to use
I2C communication with Sleep mode enabled:
•
Include in the host the logic a re-send of the Slave Address with the appropriate read or write request upon reception
of a not acknowledge.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
19
Functional Description
Figure 13. CRTouch wakeup using I2C communication
•
Use the wakeup signal to bring the part into normal run mode before starting any I2C communication. It is important
to return the wakeup signal into its idle state (high) after the communication is finished, otherwise the part will remain
into normal run mode increasing the overall system power consumption.
When the wakeup pin is used to return the part to run mode, the system will remain in this state for 50 s. If a new
communication starts with a Start condition followed by the device slave address and a valid command for the CRTouch while
in normal run mode, the part will remain in run state. It will return to sleep mode only after the communication remains idle for
1ms after receiving a stop condition. When the part wakes by receiving its slave address through I2C, it remains in run mode
for 1ms waiting for a new communication to start. It goes back to sleep mode after 1 ms of inactivity on the I2C bus.
2.3.2.3
UART communication in sleep mode
When UART communication is used for CRTouch, a start bit will transition the part from sleep mode to run mode. When the
part is in sleep mode the internal clock used for the UART communication is off. Upon reception of a start bit the internal clock
is re-started, the part returns into normal run mode and the communication can be resumed normally.
In the majority of the cases the byte that wokeup the part is properly received and stored. The exception to this rule occurs when
the internal circuitry is transitioning from normal run mode (either because of a previous communication, wakeup pin use, or
screen X and Y coordinates calculation) into sleep mode. If the UART start bit is received at the exact moment the internal
circuitry starts the transition, the initial byte (start of frame) will be lost. This will result in a complete frame loss when it occurs.
There are three alternatives when enabling Sleep mode using UART:
•
•
•
2.3.3
Send the start of frame byte twice in each frame.
Asserting the wakeup pin for at least 10 s before sending the start of frame. It is important to return the wakeup signal
into its idle state (high) after the communication is finished, otherwise the part will remain in normal run mode
increasing the overall system power consumption.
Implementing a timeout on the host side to retry the command if there is no response received within the next 1ms of
sending the command.
Shutdown mode
Shutdown is enabled through the SHUTDOWN bit in the Configuration register. This mode sends the part into the lowest power
consumption state. In this mode, all the resistive touchscreen scanning, serial communication and any other internal activity are
stopped. This mode is intended for when a device is in a standby or hibernating state and wishes to reduce power consumption
to its minimum.
There are three ways to come out of Shutdown mode:
•
•
•
Asserting the wakeup signal for more than 10 s
Using the reset pin
Optionally enabling a capacitive electrode as wakeup source and performing a touch on it.
In all cases the part will recover the latest value for the configuration registers and will resume will resume normal operating
mode. The part will use either normal run mode or Sleep mode based on the latest configuration for the SLEEPEN bit before
going into Shutdown.
CRTouch Data Sheet, Rev. 3
20
Freescale Semiconductor
Functional Description
Any of the capacitive electrodes may be enabled as a Low Power Electrode and can be configured for a scanning period and
sensitivity. To enable this electrode as a wakeup source from Shutdown, the CLPEN bit must be enabled in the Capacitive
System Configuration register. Enabling this bit inhibits normal functioning of all the electrodes, therefore it should only be
enabled prior to sending the device into Shutdown mode. Baseline tracking is not performed for the Low Power Electrode.
2.4
Internal voltage regulator
The voltage regulator module is a LDO linear voltage regulator to provide 3.3 V power from an input power supply varying
from 2.7 V to 5.5 V. It consists of one 3.3 V power channel. The internal voltage regulator can be used to be the main power
supply of the device. When the input power supply is below 3.6 V, the regulator goes to pass-through mode.
2.4.1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2.4.2
Internal voltage regulator features
Low drop-out linear voltage regulator with one power channel (3.3 V)
Low drop-out voltage— 300 mV.
Output current—120 mA.
Three different power modes— RUN, SLEEP, and SHUTDOWN.
Low quiescent current in RUN mode.
Typical value is around 120 A (one thousand times smaller than the maximum
load current).
Very low quiescent current in STANDBY mode.
Typical value is around 1 A.
Automatic current limiting if the load current is greater than 290 mA.
Automatic power-up once some voltage is applied to the regulator input.
Pass-through mode for regulator input voltages less than 3.6 V
Small output capacitor— 2.2 F
Stable with aluminum, tantalum, or ceramic capacitors.
Internal voltage regulator modes of operation
The regulator has these power modes:
•
RUN— The regulating loop of the RUN regulator and the SLEEP regulator are active, but the switch connecting the
SLEEP regulator output to the external pin is open.
• SLEEP— The regulating loop of the RUN regulator is disabled and the standby regulator is active. The switch
connecting the SLEEP regulator output to the external pin is closed.
• SHUTDOWN— The module is disabled.
This is the recommended connections to power CRTouch from internal voltage regulator:
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
21
Serial Communications
Figure 14. Connections to power CRTouch from internal voltage regulator
Figure 15. Recommended connections to power external circuitry from internal voltage regulator
3
Serial Communications
The CRTouch is a four wire and five wire resistive touch Screen and a four key capacitive touch sensing device. It can interact
with a master device either through UART or I2C interfaces
3.1
I2C interface
The registers inside CRTouch can be accessed through the Inter-Integrated Circuit serial interface (I2C, I2C, or IIC). The I2C
interface provides a method of communication with a number of devices and the CRTouch can act only as a slave device inside
an I2C network, therefore it will respond to read and write operations from a Bus master and can never initiate a communication
within the bus. To enable the I2C interface, COM SEL must be tied high when coming out of reset.
CRTouch operates as an I2C slave that sends and receives data through the SDA line on an I2C bus. A bus master initiates all
data transfers to and from CRTouch, and generates the SCL clock that synchronizes the data transfer.
The CRTouch line operates as an open drain bidirectional signal. A pull-up resistor (typically between 4.7  and 10 K) is
required on CRTouch. For CRTouch, SCL is an input only signal which also requires an external pull-up.
Each transmission is initiated with a START condition generated by the master, followed by the CRTouch slave address (7 bits)
plus one bit that indicates if the transaction is a read or write operation, in the case of write sequences it includes one register
address byte and 1 to N data bytes for read or write transactions, followed by a STOP condition that indicates the end of that
transmission.
CRTouch Data Sheet, Rev. 3
22
Freescale Semiconductor
Serial Communications
Figure 16. I2C START and STOP conditions and timing
3.1.1
I2C bit transfer
Because CRTouch can operate with different voltages, the levels of the logical low and high values are not fixed and depend on
the associated level of VDD.
The data on the SDA line must be stable during the HIGH period of the clock. Any change on the SDA line for data transmission
can only occur when the clock signal on the SCL line is LOW.
Figure 17. Bit Transfer
3.1.2
I2C START and STOP conditions
A transition to low on the SDA line while SCL is high indicates a start (S) condition. A transition to high on the SDA line while
SCL is high defines a STOP (P) condition.
START and STOP conditions are always generated by the master. The bus is free when no master device is engaging the bus
(both SCL and SDA are high). When the bus is free, a master may initiate communication by sending a START signal. The bus
is considered to be busy after the START condition. The bus is considered to be free again at a certain time after the STOP
condition.
The bus stays busy if a repeated START (Sr) is generated instead of a STOP condition. The START (S) and repeated START
(Sr) are functionally identical, therefore the S symbol will be used as a generic term to represent both the START and repeated
START conditions, unless Sr is particularly relevant.
Figure 18. START and STOP conditions
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
23
Serial Communications
3.1.3
I2C transferring data
The number of bytes that can be transmitted per transfer is unrestricted. Each byte has to be followed by an acknowledge bit.
Data is transferred with the most significant bit (MSB) first. Within each byte, there must be 8-data bits and one acknowledge
bit.
3.1.4
I2C acknowledge
Data transfer with acknowledge is obligatory for the I2C protocol. The acknowledge-related clock pulse is generated by the I2C
master as a 9th bit which the recipient uses to handshake reception of each byte of data. Thus each byte transferred effectively
requires 9 bits. To acknowledge a byte, the device sending data through the I2C bus releases the CRTouch line in the 9th bit of
data. In this clock the receiver has to pull down and maintain the CRTouch line stable low during the high period of this clock
pulse as an acknowledgement that the byte was received properly.
When CRTouch does not acknowledge a byte in a transaction it can indicate one of the following conditions:
•
•
The address is trying to be accessed (either read or write) does not exist in the memory map
The location written does not have write attributes
If the CRTouch does not acknowledge the data byte, the CRTouch line is left high during the acknowledge clock bit and the
master has to generate a STOP or repeat START condition.
Figure 19. I2C Acknowledge
3.1.5
CRTouch I2C slave address
The CRTouch has a 7-bit long slave address. The eight bit following the slave address is the R/W bit used to indicate if the
transaction is going to be a Read or Write transaction (low indicates a write command).
The I2C address has a configurable bit through the AddrSel signal. When connected to ground, bit 1 of the I2C address will be
0 and 1 when connected to VDD. The resulting two 7 bit addresses possible are: 0x49 and 0x4B.
Figure 20. I2C Slave Address
CRTouch Data Sheet, Rev. 3
24
Freescale Semiconductor
Serial Communications
3.1.6
Message format for Writing CRTouch
A write sequence comprises the transmission of the CRTouch slave address with a value of 0 for the R/W bit followed by two
bytes of information. The first byte of information is the memory map address byte and the second byte is the first data byte to
be written.
The memory map section of this document details the address of each register, its read and write permissions and the auto
increment address in case more than 1 data byte is written. Any byte received after the address byte is taken as data bytes and
is written in the location where the internal memory map logic points at that moment. A Not Acknowledge may be generated
if the location written does not exist or does not have write permissions.
Figure 21. I2C Write sequence
3.2
UART
The CRTouch device can also send and receive data through a UART communication. Default configuration is 115200 bps, 8
data bits, odd parity and one stop bit. The only configurable parameter is the baud rate through the auto-detection feature. All
the other settings are fixed.
To synchronize start and end of transactions with a host device, UART communication uses a start and end of frame reserved
characters. All the data within the data payload will be sent in unpacked BCD (that is a value of 0 x 8C will be sent in two bytes,
0 x 08 and 0 x 0C) to avoid overlapping with the start and end of frame characters.
Because there are TX and RX dedicated lines for the UART communication, for any command (read or write) there must be a
response from CRTouch, either replying to a read transaction or replying a status byte (success or error) from the previous
transaction.
3.2.1
UART Baudrate auto detection
The CRTouch comes with an auto detect feature that allows configuring any baudrate from 9600 bps to 115200 bps. To use this
feature:
1.
2.
3.
Baudrate auto detection signal is asserted with a LOW value.
Host sends three consecutive bytes with 0 x 55 values with 8-data bits, odd parity, and one stop bit at the desired
baudrate to configure.
Finally new baudrate is configured on CRTouch.
If the requested baudrate is out of range or the values sent are not the appropriate ones to calculate a valid baudrate the last valid
value stored on the memory map is used and a Baudrate error will be indicated in the Status Error register.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
25
Serial Communications
3.2.2
UART communication protocol
The protocol uses the following format:
Figure 22. UART protocol format
Start of Frame — A specific byte that indicates the start of a communication between a host and CRTouch. Data byte value
0 x C0 is used for this purpose.
Register Address — Includes information if there is a write or read request from the MCU host to CRTouch, and data record
address from the CRTouch memory map. Data record address is 7-bits width, from Bit 6 to Bit 0 and write/read transaction is
located on [B7]. B7 LOW Indicates a Read transaction.
Payload Size — Information about quantity of bytes to be read or written is included on this field, this size does not include
start of frame, register address, nor end of frame.
Data bytes —Write or Read information from the the memory map. The numbers of bytes to be read or written specified in the
payload size define how many bytes each frame has. Section 4.1, “Device memory map” includes a description of the registers
address and the next address to be written or read in case of a sequential read/write operation.
End of Frame (EOF) — EOF indicates that the current communication has been finished. If the data frame transmitted from
the host MCU to the CRTouch does not include an EOF (0 x C1), the information sent from the Host to CRTouch does not have
any effect. When processing data through UART interface the command is executed upon the reception of an EOF.
Starting on the data record address byte to the last data byte to be transmitted or received by the host MCU, each data byte is
divided in MSB nibble and LSB nibble where the valid range written goes from 0 x 00 to 0 x 0F.
3.2.3
Registers Read through UART
To read any CRTouch register using the UART interface, the communication must start with a SOF followed by a register
address with the most significant bit value of ‘0’ and the amount of bytes that the host wishes to read followed by an EOF.
Upon reception of a read command, CRTouch will reply using the same UART communication protocol (SOF, Register
Address, Payload Size, Data Payload, and EOF) with the data from the registers read.
Figure 23. Register read through UART communication
CRTouch Data Sheet, Rev. 3
26
Freescale Semiconductor
Serial Communications
Table 6. UART communication responses to a write command
Byte Value
3.2.4
Information
0xC2
Positive Acknowledge. The last command data was valid and has been properly
written into CRTouch.
0xE0
Sampling rate out of range. A value between 5 and 100 (ms) is expected.
0xE1
Invalid write transaction. Register written does not have write attributes
0xE2
Data size out of range. A value between 1 and tes sent in the write command
0xE3
Register Address out of range. See memory map section for more information
0xE5
Parity Error was generated. Parity is odd parity for each byte.
Registers Write through UART
To write one to n CRTouch registers, the communication must start with a SOF, followed by a register address with the most
significant bit value of ‘1’ indicating the amount of registers to be written, followed by the data bytes and ending with an EOF.
The CRTouch will reply either with an acknowledge byte or an error code.
Figure 24. Register write through UART communication
The following table shows a list of possible responses to a write commands from a host. Response to any write command is the
only communication where the communication protocol is not strictly followed to reduce the amount of traffic generated for a
simple acknowledgement.
Table 7. UART communication responses to a write command
Byte Value
Information
0xC2
Positive Acknowledge. The last command data was valid and has been properly written into CRTouch.
0xE0
Sampling rate out of range. A value between 5 and 100 (ms) is expected.
0xE1
Invalid write transaction. Register written does not have write attributes
0xE2
Data size out of range. A value between 1 and test sent in write command
0xE3
Register Address out of range. See memory map section for more information
0xE5
Parity Error was generated. Parity is odd parity for each byte.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
27
Memory Map and Registers Description
4
Memory Map and Registers Description
The CRTouch product has status and configuration registers for the resistive touchscreen driver and the capacitive keys support.
All the status registers are read-only registers. The configuration registers have read and write attributes. All configuration
registers are stored in non-volatile memory when changed, the device therefore does not require reconfiguration after power
loss or reset. Only specific bits in certain registers are not restored and this is indicated in the corresponding bit description.
When writing a configuration value into a register, it may take one sampling period, resistive or capacitive, for it to take effect
and to be read.
4.1
Device memory map
The CRTouch memory map is designed to allow a consecutive bytes reading. Each register has a value for its incremental
address, which is the value that the internal read address pointer holds after reading that specific location. For example, if the
X coordinate is read, the initial transaction starts with address 0x03 and automatically auto-increment to 0x04, 0x05, and 0x06.
When the pressure is disabled, after reading the Y coordinate LSB in address 0x06, the internal address pointer returns to value
0x03 to allow reading again of X and Y coordinates without further write operations.
Table 8. Resistive touch sense status register map
Name
Register
address
Incremental
Address
Default Value
Valid Range
Comment
Resistive Touch Error
Register
0x00
0x01
0x00
—
Used to report Serial
Protocol communication
errors
Resistive Touch Status
Register 1
0x01
0x02
0x00
—
Register used to report
general information
Resistive Touch Status
Register 2
0x02
0x03
0x00
—
Register used to report
general information
X coordinate MSB
0x03
0x04
0x00
0x00 – 0x1F
X coordinate MSB
X coordinate LSB
0x04
0x05
0x00
0x00 – 0xFF
X coordinate LSB
Y coordinate MSB
0x05
0x06
0x00
0x00 – 0x1F
Y coordinate MSB
Y coordinate LSB
0x06
0x031
0x072
0x00
0x00 — 0xFF
Y coordinate LSB
Pressure value MSB
0x07
0x08
0x00
0x00 — 0xFF
Pressure value MSB
Pressure value LSB
0x08
0x03
0x00
0x00 — 0xFF
Pressure value LSB
Resistive Touch FIFO
Status
0x09
0x0A
0x00
—
FIFO Status information
FIFO X coordinate MSB 0x0A
0x0B
0x00
0x00 — 0x1F
FIFO X coordinate MSB
FIFO X coordinate LSB
0x0B
0x0C
0x00
0x00 — 0xFF
FIFO X coordinate LSB
FIFO Y coordinate MSB 0x0C
0x0D
0x00
0x00 — 0x1F
FIFO Y coordinate MSB
FIFO Y coordinate LSB
0x0D
0x0A1
0x0E2
0x00
0x00 — 0xFF
FIFO Y coordinate LSB
FIFO Pressure value
coordinate MSB
0x0E
0x0F
0x00
0x00 — 0xFF
FIFO Pressure value
coordinate MSB
CRTouch Data Sheet, Rev. 3
28
Freescale Semiconductor
Memory Map and Registers Description
Table 8. Resistive touch sense status register map (continued)
Register
address
Name
Incremental
Address
Default Value
Valid Range
Comment
FIFO Pressure value
coordinate LSB
0x0F
0x10
0x00
0x00 — 0xFF
FIFO Pressure value
coordinate LSB
UART baudrate MSB
0x10
0x11
0x01
0x00 — 0x01
UART baud rate MSB
byte
UART baudrate MID
0x11
0x12
0xC2
0x00 — 0xFF
UART baud rate MID byte
UART baudrate LSB
0x12
0x13
0x00
0x00 — 0xFF
UART baud rate LSB
byte
Device Identifier Register 0x13
0x14
0x12
—
Identifies mask set of the
device. Increments with
versions of the device.
Slide displacement
0x14
0x15
0x00
0x00 — 0xFF
Reports how many steps
the user displaced since
the initial touch
Rotate angle
0x15
0x16
0x00
0x00 — 0xFF
Reports the total angle of
the rotate motion since
the initial touch
Zoom size
0x16
0x20
0x00
0x00 — 0xFF
Reports how much zoom
has been exercised by
the user
1.Incremental address when pressure detection is disabled.
2.Incremental address when pressure detection is enabled.
Table 9. Capacitive Touch Status registers
Name
Register
Address
Incremental
Address
Default
Value
Valid Range
Comment
Electrode Status 0x20
0x21
0x00
0x00 — 0x0F Each bit represents the current status of an
electrode.
Capacitive Touch 0x21
Faults
0x22
0x00
0x00 to 0x01 Shows the faults generated by the system
Electrode 0
baseline MSB
0x22
0x23
Electrode 0
baseline LSB
0x23
0x24
Electrode 1
baseline MSB
0x24
0x25
Electrode 1
baseline LSB
0x25
0x26
Electrode 2
baseline MSB
0x26
0x27
Electrode 2
baseline LSB
0x27
0x28
0x0000
0x0000
0x0000
0x0000 –
0x07FF
0x0000 –
0x07FF
0x0000 –
0x07FF
Electrode base capacitance. This value may
adjust to changes due to electrical and
environmental noise.
Electrode base capacitance. This value may
adjust to changes due to electrical and
environmental noise.
Electrode base capacitance. This value may
adjust to changes due to electrical and
environmental noise.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
29
Memory Map and Registers Description
Table 9. Capacitive Touch Status registers
Name
Register
Address
Incremental
Address
Electrode3
baseline MSB
0x28
0x29
Electrode3
baseline LSB
0x29
0x2A
Electrode0
instant delta
0x2A
Electrode1
instant delta
Default
Value
Valid Range
Comment
Electrode base capacitance. This value may
adjust to changes due to electrical and
environmental noise.
0x0000
0x0000 –
0x07FF
0x2B
0x00
-128 — 127
Instant capacitance variation with respect to
its baseline
0x2B
0x2C
0x00
-128 — 127
Instant capacitance variation with respect to
its baseline
Electrode2
instant delta
0x2C
0x2D
0x00
-128 — 127
Instant capacitance variation with respect to
its baseline
Electrode3
instant delta
0x2D
0x2E
0x00
-128 — 127
Instant capacitance variation with respect to
its baseline
Slider and
0x2E
Rotary Dynamic
Status
0x2F
0x00
—
Displays the movement, direction, and
displacement information
Slider and
Rotary Static
Status
0x2F
0x20
0x00
—
Displays the touch and absolute position
information. Holds the invalid position status
flag
Capacitive
0x30
Electrodes FIFO
0x30
0x00
—
Register window for keypad FIFO.
Consecutive reads to this register return
successive FIFO elements.
Table 10. Resistive Touch Configuration register map
Name
Register Incremental
address
Address
Default
Value
Valid Range
Comment
Resistive Touch
0x40
System Configuration
0x41
0x00
0x00 — 0xFF General CRTouch configuration register
Resistive Touch
Trigger events
0x41
0x42
0x00
0x00 — 0xFF Register used to select what event shall
assert port pin event signal
Resistive Touch FIFO
Setup
0x42
0x43
0x00
0x00 — 0x1F FIFO enabler and watermark are
configured in this register
Sampling rate X and Y 0x43
coordinates (msec)
0x44
0x05
0x05 — 0x64 Determines the resistive touchscreen
sampling rate in milliseconds
X Settling Time MSB
0x45
0x44
X Settling Time LSB
0x45
0x46
Y Settling Time MSB
0x46
0x47
Y Settling Time LSB
0x47
0x48
Z Settling Time MSB
0x48
0x49
Z Settling Time LSB
0x49
0x4A
X Settling time high byte
0x0064
0x000E –
0x012C
0x0064
0x000E –
0x012C
X Settling time low byte
Y Settling time high byte
0x0064
0x000E –
0x012C
Y Settling time low byte
Z Settling time high byte
Z Settling time low byte
CRTouch Data Sheet, Rev. 3
30
Freescale Semiconductor
Memory Map and Registers Description
Table 10. Resistive Touch Configuration register map (continued)
Name
Register Incremental
address
Address
Display Horizontal
resolution MSB
0x4A
Display Horizontal
resolution LSB
0x4B
0x4C
Display Vertical
resolution MSB
0x4C
0x4D
Display Vertical
resolution LSB
0x4D
0x4E
Resistive Touch Slide
steps
0x4E
0x4F
Default
Value
Valid Range
0x4B
0x1000
0x1000
0x1000
0x0030 –
0x2000
0x0030 –
0x2000
Comment
MSB of the display resolution on the X
axis
LSB of the display resolution on the X
axis
MSB of the display resolution on the Y
axis
LSB of the display resolution on the Y
axis
0x0A
0x01 — 0xFF Defines how many slides per axis may
be detected
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
31
Memory Map and Registers Description
Table 11. Calibration Values registers map
Name
Register
Address
Incremental
Address
X Calibration Value 1
MSB
0x4F
0x50
X Calibration Value 1
LSB
0x50
0x51
X Calibration Value 2
MSB
0x51
0x52
X Calibration Value 2
LSB
0x52
0x53
X Calibration Value 3
MSB
0x53
0x54
X Calibration Value 3
LSB
0x54
0x55
Y Calibration Value 1
MSB
0x55
0x56
Y Calibration Value 1
LSB
0x56
0x57
Y Calibration Value 2
MSB
0x57
0x58
Y Calibration Value 2
LSB
0x58
0x59
Y Calibration Value 3
MSB
0x59
0x5A
Y Calibration Value 3
LSB
0x5A
0x5B
X Calibration Constant
MSB
0xB
0x5C
X Calibration Constant
LSB
0x5C
0x5D
Y Calibration Constant
MSB
0x5D
0x50E
Y Calibration Constant
LSB
0x5E
0x60
Default
Value
Valid Range
0x4000
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
0x4000
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
0x0
0x0000 –
0xFFFF
Comment
Manual calibration values.
Writing to these registers
calibrates the device without
the need for pressing the
calibration points on the
touchscreen.
CRTouch Data Sheet, Rev. 3
32
Freescale Semiconductor
Memory Map and Registers Description
Table 12. Capacitive Touch Configuration registers map
Name
Register
address
Incremental
Address
Default
Value
Valid
Range
Comment
Capacitive System
Configuration
0x60
0x61
0x20
—
Main configuration of the capacitive
touch system
DC Tracker Rate
0x61
0x62
0x0A
0x00 –
0xFF
Determines how often the
recalibration function occurs.
Capacitive Touch
ResponseTime
0x62
0x63
0x04
0x00 –
0x20
Configures the number of scans
necessary to determine if a key is
pressed
StuckKeyTimeout
0x63
0x64
0x64
0x00 —
0xFF
Configures the number of scans to
detect a key stuck
Electrode0 Sensitivity
0x64
0x65
0x40
0x02 –
0x7F
Represents the capacitance threshold
for electrode 0 to be detected as
touched
Electrode1 Sensitivity
0x65
0x66
0x40
0x02 –
0x7F
Represents the capacitance threshold
for electrode 1 to be detected as
touched
Electrode2 Sensitivity
0x66
0x67
0x40
0x02 –
0x7F
Represents the capacitance threshold
for electrode 2 to be detected as
touched
Electrode3 Sensitivity
0x67
0x68
0x40
0x02 –
0x7F
Represents the capacitance threshold
for electrode 3 to be detected as
touched
Electrodes Enablers
0x68
0x69
0x0F
—
Each bit represents the enabler of an
electrode. If a bit is 0, then the
corresponding electrode will not be
scanned
Capacitive touch Low power
scan period
0x69
0x6A
0x0F
0x00 –
0x0F
Represents the value of the scan
period in low power mode
Capacitive Touch Low power
electrode
0x6A
0x6B
0x00
0x00 –
0x03
This register represents the number of
the electrode scanned in low power
mode
Low power electrode
sensitivity
0x6B
0x6C
0x7F
0x00 –
0x7F
Threshold for the low power electrode
while in shutdown mode
Capacitive Resolution
0x6C
0x6D
0x0A
0x08 –
0x0B
Determines the resolution in bits of the
capacitive samples
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
33
Memory Map and Registers Description
Table 12. Capacitive Touch Configuration registers map
Register
address
Name
Incremental
Address
Default
Value
Valid
Range
Comment
Capacitive Touch Events
0x6D
0x6E
0x01
0x00 –
0xFF
Configures the events that reported by
the capacitive controller
Capacitive Touch
AutoRepeatRate
0x6E
0x6F
0xFF
0x00 –
0xFF
Configures the rate at which keys will
be reported when kept pressed
Capacitive Touch
AutoRepeatStart
0x6F
0x70
0xFF
0x00 –
0xFF
Configures the time between a touch
and an auto-repeat event when the
key is kept pressed
Capacitive MaxTouches
0x70
0x71
0x00
0x00 –
0x03
Configures the maximum number of
keys that can be pressed at once
4.2
Registers description
4.2.1
Resistive Touch Status registers
All the Resistive touch status registers have read only attributes. Attempting to write any of these registers return in an invalid
write response from CRTouch.
4.2.1.1
Resistive Touch Error Register
This register reports several possible failures in the system. All bits are cleared after a register read
Bit
Field
7
6
5
4
3
2
1
0
BRE
CE
SE
WEF
DSE
AE
EOFE
PE
Field
Description
7
BRE
Baudrate error
BRE is set when the baud-rate auto detect process can not determine the communication baudrate.
6
CE
Calibration error flag
Set when the calibration process can not calculate the values needed for system calibration. This
typically occurs when the points touched do not match with calibration requirements.
5
SE
Sampling error flag
Set when trying to write the resistive touch sampling rate register with a value less than 5 or more
than 100.
4
WEF
Write Error Flag
WEF is set when trying to write an address that has read-only attributes.
CRTouch Data Sheet, Rev. 3
34
Freescale Semiconductor
Memory Map and Registers Description
Field
3
DSE
2
AE
Description
Data Size Error
DSE is set when Number of data = 0 or Number of data > 101.
Address Error
AE is set when the requested address is outside the address memory map range or within an
un-implemented section of the memory map.
1
EOFE
End of Frame Error
EOF error flag is set to 1 when end of frame is not received after the communication timeout expires.
0
PE
Parity Error
PE error flag is set to 1 when one or several bytes from the received frame does not have odd parity
properly configured.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
35
Memory Map and Registers Description
4.2.1.2
Resistive Touch Status register 1
This register reports different events that may be detected in the system, and latches some bits to ensure
that the event does not get lost if not read immediately. Latched bits clear after a register read. The
TouchPending pin is also set after this register is read.
Bit
Field
Field
7
RTST
7
6
5
4
3
2
1
0
RTST
RTS2T
RTSZ
RTSR
RTSS
RTSF
CTE
RTSRDY
Description
Resistive Touch Screen Touched is set after any touch event in a resistive screen is connected to
CRTouch
0 Resistive touch screen not currently touched
1 Resistive touch screen currently touched
6
RTS2T
Resistive touch screen Two Touch detection is set after the screen has a two touch detection event.
This bit is automatically cleared when a two touch condition is no longer detected on the screen.
0 Two touch event not currently detected
1 Two touch currently detected.
5
RTSZ
Resistive Touch Screen Zoom indicates when a zoom gesture has been detected.
0 Zoom gesture not detected
1 Zoom gesture pending for reading
4
RTSR
Resistive Touch Screen Rotate indicates when a rotate gesture has been detected.
0 Rotate gesture not detected
1 Rotate gesture pending for reading
3
RTSS
Resistive Touch Screen Slide indicates when a slide gesture has been detected.
0 Slide gesture not pending for reading
1 Slide gesture pending for reading
2
RTSF
Resistive touch screen FIFO data is set when the FIFO count reaches the watermark value or when
the FIFO is filled.
0 FIFO data ful and watermark reached
1 FIFO data not full and watermark not reached
1
CTE
Capacitive touch event is set after one of the configured capacitive events is detected.
0 Capacitive touch event not pending for reading
1 Capacitive touch event pending for reading
0
Resistive Touch Sample ready is set after a resistive touch screen connected to CRTouch is pressed
RTSRDY and the device finished all the data processing to determine X and Y coordinates.
0 Resistive touch sample not pending for reading
1 Resistive touch sample pending for reading
CRTouch Data Sheet, Rev. 3
36
Freescale Semiconductor
Memory Map and Registers Description
4.2.1.3
Resistive Touch Status Register 2
Bit
Field
7
6
5
4
RTSCAL
Reserved
RTSZD
RTSRD
Field
3
2
1
0
RTSSD
RTSD
Description
7
Resistive Touch screen calibrated is set after the screen has been properly calibrated. After initial calibration the
RTSCAL result is stored in the internal non-volatile memory and is recovered after automatically reset.
0 Resistive touch screen not calibrated
1 Resistive touch screen calibrated
This bit is reserved
6
Reserved
5
RTSZD
Zoom direction
0 Zoom in
1 Zoom out
4
RTSRD
Resistive Touch Screen Rotate Direction.
0 Clock wise direction
1 Counter clock wise direction
3-2
RTSSD
Resistive Touch Screen Slide Direction indicates the direction of the slide gesture after its detection.
1-0
RTSTD
4.2.1.4
Bit
0
0
Horizontal positive direction
0
1
Horizontal negative direction
1
0
Vertical positive direction
1
1
Vertical negative direction
Resistive Touch Screen type detected. After reset, the system scans for the type of resistive touch screen
connected to the system. The RTSD bits indicate the type of screen detected.
0
0
Resistive touch not detected
0
1
4 wires resistive touch screen detected
1
0
5 wires resistive touch screen detected
1
1
Reserved
X coordinate
15
Field
14
13
12
11
10
9
8
7
6
XMSB
5
4
3
2
1
0
XLSB
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
37
Memory Map and Registers Description
Signal
4.2.1.5
Bit
Description
15-8
XMSB
Most significant Byte for X coordinate
7-0
XLSB
Least significant Byte for X coordinate
Y coordinate
15
14
13
12
Field
11
10
9
Bit
Field
5
4
3
2
1
0
2
1
0
YLSB
15-8
YMSB
Most significant Byte forY coordinate
7-0
YLSB
Least significant Byte for Y coordinate
Pressure value
15
14
13
12
11
10
9
8
7
6
5
PRESSMSB
4
3
PRESSLSB
Signal
Bit
6
Description
Field
4.2.1.7
7
YMSB
Signal
4.2.1.6
8
Description
15-8
PRESSMSB
Most significant Byte for Pressure detected when touching the screen
7-0
PRESSLSB
Least significant Byte for Pressure detected when touching the screen
Resistive Touch FIFO status
7
6
5
4
Reserved
Reserved
FIFOWMRKF
FIFOWMRKF
3
2
1
0
FIFOCNT
CRTouch Data Sheet, Rev. 3
38
Freescale Semiconductor
Memory Map and Registers Description
Signal
Description
7
Reserved
Reserved
6
Reserved
Reserved
5
FIFOWMRKF
FIFO Watermark Flag indicates when the FIFO counter is greater than or equal to the value
configured in the WaterMark bits of the FIFO Configuration register.
4-0
FIFOCNT
FIFO sample counter, default value 00000. (00001 to 11111 indicates 1 to 31 samples stored
in FIFO)
4.2.1.8
Bit
FIFO X coordinate
15
14
13
Field
12
11
10
9
Bit
5
4
3
2
1
0
2
1
0
2
1
0
FIFOXLSB
15-8
FIFOXMSB
Most significant Byte for X coordinate stored in the FIFO
7-0
FIFOXLSB
Least significant Byte for X coordinate stored in the FIFO
FIFO Y coordinate
15
14
13
12
11
10
9
8
7
6
5
4
FIFOYMSB
3
FIFOYLSB
Signal
Bit
6
Description
Field
4.2.1.10
7
FIFOXMSB
Signal
4.2.1.9
8
Description
15-8
FIFOYMSB
Most significant Byte for Y coordinate stored in the FIFO
7-0
FIFOYLSB
Least significant Byte for Y coordinate stored in the FIFO
FIFO Pressure Value
15
14
Field
13
12
11
10
9
8
7
FIFOPMSB
6
5
4
3
FIFOPLSB
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
39
Memory Map and Registers Description
Signal
4.2.1.11
Bit
23
Description
15-8
FIFOPMSB
Most significant Byte for Pressure stored in the FIFO
7-0
FIFOPLSB
Least significant Byte for Pressure stored in the FIFO
UART baudrate MSB (read only)
22
21
Field
20
19
18
17
16
15
BRH
Bit
Bit
Field
11
10
9
8
7
6
5
4
3
2
1
0
BRL
Description
23-16
FIFOYMSB
Most significant Byte for UART baudrate used for the system configuration.
15-8
FIFOYLSB
Intermediate Byte for UART baudrate used for the system configuration.
7-0
FIFOYLSB
Least significant Byte for UART baudrate used for the system configuration.
Device identifier register (read only)
7
6
5
Field
4.2.1.13
13 12
BRM
Signal
4.2.1.12
14
4
3
2
1
0
DEVICEID
Signal
Description
7-0
DEVICEID
Device ID stores the product version information. This register is factory programmed and
its usage is for traceability purposes.
Slide displacement
7
6
5
4
3
2
1
0
SLIDEDATA
CRTouch Data Sheet, Rev. 3
40
Freescale Semiconductor
Memory Map and Registers Description
4.2.1.14
Bit
Signal
Description
7-0
SLIDEDATA
Reports how many steps the user has displaced after the initial touch. This is useful to
keep track of the motion if at lower sampling rates, more than one step was displaced in
a sample period.
Rotate angle
7
6
5
4
Field
7-0
ROTATEDATA
Bit
1
0
1
0
Description
Reports the total angle of the rotate motion after the initial touch.
Zoom size (read only)
7
6
5
4
Field
3
2
ZOOMSIZE
Signal
7-0
ZOOMSIZE
4.2.2
2
ROTATEDATA
Signal
4.2.1.15
3
Description
Reports how much zoom has been exercised by the user.
Capacitive Touch Sensing Status registers
All the Capacitive Touch Sensing Status registers have read only attributes. Attempting to write any of these registers will return
an invalid write response from CRTouch.
4.2.2.1
Bit
Capacitive Electrodes Status register
7
Field
6
5
4
Reserved
3
2
1
0
E3
E2
E1
E0
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
41
Memory Map and Registers Description
Signal
Description
7-4
Reserved
Reserved
3-0
E3-E0
4.2.2.2
E3 – E0 represents the status of the corresponding electrode. A bit set to
1 indicates that the corresponding electrode is detecting a touch event.
Capacitive Touch Faults register
Bit
7
6
5
Field
4
Bit
Bit
Field
1
0
SE
Description
7-1
Reserved
Reserved
0
Shortened
Electrode
Indicates if one of the capacitive electrodes cannot be measured, typically
due to a short to Vcc or ground.
1 Timeout fault detected
0 No timeout fault detected
Electrodes Baselines registers
15
14
Field
4.2.2.4
2
Reserved
Signal
4.2.2.3
3
13
12
11
10
9
8
7
6
5
ExBASELINEMSB
4
3
2
1
0
ExBASELINELSB
Signal
Description
15-8
Electrode Baseline
MSB
Most significant Byte for Electrodes 0 to 3 baseline. The baseline value is compared
to the instant value to determine if the electrode is touched or not.
7-0
Electrode Baseline
LSB
Least significant byte for electrodes 0 to 3 baseline. The baseline value is compared
to the instant value to determine if the electrode is touched or not.
Electrodes instant Delta registers
7
6
5
4
3
2
1
0
ExINSTANTDELTA
CRTouch Data Sheet, Rev. 3
42
Freescale Semiconductor
Memory Map and Registers Description
4.2.2.5
Bit
Field
4.2.2.6
Bit
Field
Signal
Description
7-0
Electrode Instant
Delta
Electrode 3 to Electrode 0 instant capacitance variation with respect to its baseline.
This register is in signed format, ranging from -128 to 127. If the instant value is
greater than these values, the Delta value is saturated.
Slider and rotary dynamic status
7
6
CTDSMOV
CTDSDIR
5
4
3
2
Reserved
1
0
CTDSVAL
Signal
Description
7
CTDSMOV
Capacitive Touch Dynamic Status Movement indicates if movement is being detected at
the moment of reading. 1 Indicates that there is movement detected
6
CTDSDIR
Capacitive Touch Dynamic Status Direction is used to determine the direction of
movement. 1 indicates an incremental movement. This bit remains with its last value even
if movement has stop and is no longer detected.
5-4
Reserved
Reserved
3-0
CTDSVAL
Capacitive Touch Dynamic Status value indicates the difference in positions from the last
status to the new one. This indicates how many positions have been advanced in the
current direction of movement.
Slider and rotary static status
7
6
5
CTSSTOUCH
CTSSINV
Reserved
4
3
2
1
0
CTDSVAL
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
43
Memory Map and Registers Description
Signal
Description
7
CTSSTOUCH
Capacitive Touch Static Status Touch indicates if a touch in the control is being detected
at the moment of reading.
6
CTSSINV
Capacitive Touch Static Status Invalid flag Indicates if an invalid combination of touched
electrodes is being detected. An invalid combination is detected when two or more non
adjacent electrodes are detected as touched, for example electrodes 0 and 2.
5Reserved
Reserved
4-0
CTDSVAL
Capacitive Touch Static Status Value indicates the absolute position within the control that
is actuated.
NOTE
For rotary and sliders, the number of positions is greater than the number of electrodes. The
device reports different positions when more than one electrode is being touched. For more
details, review Section 2.2.3, “Rotary and slider control”
4.2.2.7
Capacitive electrodes FIFO (read only)
When electrodes are configured as keypad, capacitive electrodes FIFO keeps status information from capacitive electrode 0 to 3.
Bit
Field
7
6
CTFIFOTOUCH
Reserved
Signal
7
CTFIFOTOUCH
5Reserved
5-0
CTFIFOKEY
4.2.3
5
4
3
2
1
0
CTFIFOKEY
Description
Capacitive Touch FIFO Touch indicates if the event was a release or a touch event. 1
Indicates the key was released
Reserved
Capacitive Touch FIFO Key determines the key on which the event has occurred
Resistive Touch Configuration registers
All the Resistive Touch Status registers have read and write attributes. Care must be taken that the written value is valid for the
specific register written
4.2.3.1
Resistive and Capacitive Touch Configuration register
The Resistive and Capacitive Touch Configuration register is used to configure the different settings used as part of the resistive
and capacitive scanning processes. All the configuration bits except CRTSHTDWN are non-volatile and recovered to their latest
value as part of the part reset sequence.
CRTouch Data Sheet, Rev. 3
44
Freescale Semiconductor
Memory Map and Registers Description
Bit
7
Field
6
RTPRESEN
5
CTCNTRL
Field
4
3
2
1
0
RTSLDEN
RTROTEN
RTPNCEN
CRTSLEEP
CRTSHTDWN
Description
7
RTPRESEN
Resistive touch pressure enable bit is used to enable the pressure measurement on the resistive touch
screen as part of the X and Y scanning process. If FIFO is enabled, changing the value of this bit will
automatically flush the FIFO to synchronize X, Y, and pressure buffers.
6-5
CTCNTRL
Capacitive Touch Control defines the type of control used for the four capacitive electrodes that can be
connected to CRTouch.
CTCNTRL CTCNTRL
1
0
Configuration
1
1
Keypad control selected
1
0
Slider control selected
0
1
Rotary control selected
0
0
Capacitive keys disabled
4
RTSLDEN
Resistive Touch Slide Enable — A single touch slide can be detected if the X and Y coordinates fit in the
slide gesture description. Status registers 1 and 2 are used to indicate when the slide gesture was
detected and the slide direction.
3
RTROTEN
Resistive Touch Rotate Enable — Status registers 1 and 2 are used to indicate when the Rotate gesture
was detected and if it was a clock-wise or counter-clock-wise gesture.
2
RTZMEN
Resistive Touch Zoom Enable — This bit controls if zoom motions on the touch screen are detected and
reported. Status registers 1 and 2 are used to indicate when the pinch gesture is detected and if it was a
zoom-in or zoom out gesture.
1
CRTSLEEP
Capacitive Resistive Touch sleep is used to send the deviceinto sleep mode. Section 2.3.2, “Sleep mode”
has detailed information on the CRTouch behavior while in sleep mode.
1 Sleep mode enabled
0 Sleep mode disabled
0
Capacitive Resistive Touch Shutdown is used to configure the CRTouch into its lowest power mode
CRTSHTDWN available. Section 2.3.3, “Shutdown mode” has detailed information on the CRTouch behavior when this bit
is enabled. Shutdown is the only bit in the configuration register that is not restored after a reset.
1 Shutdown mode enabled
0 Shutdown mode disabled
4.2.3.2
Resistive and Capacitive Triggers register
The Resistive and Capacitive Triggers register configures what events will assert the TOUCHPENDING pin. This can be used
to signal to an external host that there is a pending activity to be read in the status registers. The Triggers register also contains
a bit used by the host to send CRTouch into calibration mode—see Section 2.1.4, “Calibration process.” All bits except for the
Calibration bit are non-volatile. A 1 enables the event to assert the TOUCHPENDING pin.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
45
Memory Map and Registers Description
Bit
Field
7
6
5
4
3
2
1
0
RTREL
RTCAL
RTPINCH
RTSLD
RTROT
RTFIFOWM
CTEV
RTEV
Description
Field
4.2.3.3
7
RTREL
Resistive touch release bit is used to generate a signal when the resistive touch screen is
released.
6
RTCAL
Resistive touch Calibration bit sends the CRTouch into calibration mode. After this bit is
enabled, the system behavior is Section 2.1.4, “Calibration process.” Writing a 0 to this bit
while in a calibration process aborts the calibration. Calibration mode is finished after the
calibration points have been identified or with a reset.
5
RTZOOM
Resistive Touch Pinch trigger bit configures the external event pin to be asserted when a
Zoom-in or Zoom out is detected.
4
RTROT
Resistive Touch Rotate trigger bit configures the external event pin asserted when a
clock-wise or counter-clock-wise rotate gesture is detected.
3
RTSLD
Resistive Touch Slide trigger bit configures the external event pin asserted when a slide
gesture in any direction is detected.
2
RTFIFOWM
Resistive Touch FIFO Watermark bit is used to generate a signal after the number of
samples in the FIFO is greater than or equal to the Watermark bits configuration in the FIFO
setup register
1
CTEV
Capacitive Touch Event is used to generate a pending activity signal when any capacitive
event is detected. Capacitive events detection is configured in the Capacitive Events
register.
0
RTEV
Resistive Touch Event signals the host after each sampling period after the signals have
been processed and the coordinates have been determined, as well as any resistive event.
FIFO Setup register
Any writes to this register will automatically flush the FIFO of any stored elements.
Bit
Field
7
6
Reserved
5
4
3
RTFIFOEN
2
1
0
RTFIFOWMRK
CRTouch Data Sheet, Rev. 3
46
Freescale Semiconductor
Memory Map and Registers Description
Field
Description
7-5
Reserved
Reserved
6
RTFIFOEN
Resistive Touch FIFO Enable enables storing the resistive touch data inside the FIFO.
3-0
RTFIFOWMRK
Resistive Touch FIFO Watermark indicates the amount of samples needed to signal an
event. When the amount of values stored in the FIFO is greater than or equal to the
watermark configuration, the RTSF bit is set in the Status Register 1.
0 Watermark is disabled. FIFO event is signaled when the FIFO is full.
1–15 FIFO event will be signaled when the FIFO counter reaches this value.
4.2.3.4
Resistive touch sampling rate
This register is used to configure the period to sample the resistive touch screen.
Bit
7
6
5
4
3
2
1
0
RTSAMPLING
Field
Signal
Description
7–0
RTSAMPLING
Value in miliseconds to indicate the scanning period. Value must be between 5 and 100 (10 points per
second to 200 points per second).
4.2.3.5
X coordinate stabilization time
This 16-bit value holds the number needed in micro-seconds for the signals required for an X coordinate scanning to stabilize.
The value is calculated automatically as part of the calibration process but can be written through serial communication to
simplify factory configuration of devices.
Bit
15
14
13
Field
12
11
10
9
8
7
6
4
3
2
1
0
XCTIMESETLSB
XCTIMESETMSB
Signal
5
Description
15–8
Most significant byte for the X coordinates stabilization delay.
X Coordinate
stabilization MSB
7–0
Least significant byte for the X coordinates stabilization delay
X Coordinate
stabilization LSB
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
47
Memory Map and Registers Description
4.2.3.6
Y coordinate stabilization time
This 16-bit value holds the number needed in micro-seconds for the signals required for a Y coordinate scanning to stabilize.
The value is calculated automatically as part of the calibration process but can be written through serial communication to
simplify factory configuration of devices.
Bit
15
14
13
Field
12
11
10
9
8
7
6
5
4
3
2
1
0
YCTIMESETLSB
YCTIMESETMSB
Signal
Description
15-8
Most significant byte for the Y coordinates stabilization delay.
Y Coordinate
stabilization MSB
7-0
Y Coordinate
Least significant byte for the Y coordinates stabilization delay
stabilization LSB
4.2.3.7
Z coordinate stabilization time
This 16-bit value holds the number needed in micro-seconds for the signals required for the pressure coordinate scanning to
stabilize. The value is calculated automatically as part of the calibration process, but can be written through serial
communication to simplify factory configuration of devices.
Bit
15
Field
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ZTIMESETLSB
ZTIMESETMSB
Signal
Description
15-8
Most significant byte for the two-touch signals stabilization delay.
Pressure
stabilization MSB
7-0
Least significant byte for the two-touch signals stabilization delay
Pressure
stabilization LSB
4.2.3.8
Display horizontal resolution
Determines the resolution for the X coordinates. It is important to configure this value properly before a calibration is executed.
Values written to this register have no effect until after both horizontal and vertical resolutions have been written. Writes to these
registers reset the device calibration.
CRTouch Data Sheet, Rev. 3
48
Freescale Semiconductor
Memory Map and Registers Description
Bit
Field
15
14
13
Reserved
Reserved
12
11
10
9
8
7
6
5
XAXISRESMSB
4
3
2
1
0
XAXISRESLSB
Signal
Description
15–14
Reserved
Reserved
13–8
Most significant byte for the X axis resolution
X Axis Resolution
MSB
7–0
Least significant byte for the X axis resolution
X Axis Resolution
LSB
4.2.3.9
Display vertical resolution
Determines the resolution for the Y coordinates. It is important to configure this value properly before a calibration is executed.
Values written to this register have no effect until after both horizontal and vertical resolutions have been written. Writes to these
registers reset the device calibration.
Bit
Field
15
14
13
Reserved
Reserved
12
11
10
9
8
7
6
5
4
3
2
1
0
YAXISRESLSB
YAXISRESMSB
Signal
Description
15–14
Reserved
Reserved
13–8
Most significant byte for the Y axis resolution
Y Axis Resolution
MSB
7–0
Least significant byte for the Y axis resolution
Y Axis Resolution
LSB
4.2.3.10
Resistive touch slide steps
Bit
Field
7
6
5
4
3
2
1
0
RTSLDSTEPS
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
49
Memory Map and Registers Description
Signal
Description
7–0
RTSLDSTEPS
4.2.4
Number of steps reported when a slide is perform side to side of the touch screen
Calibration Values registers
This set of registers hold the calibration coefficients for the X and Y single touch coordinates, as well as the constants for each
axis required for two touch gesture calculations. Writing to these values calibrates the device without the need for touching the
calibration points on the screen. All of the values must be written to calibrate the device. The Status Register 2 bit for calibration
is set after a reset.
4.2.4.1
X calibration values
This set of three 16-bit values represents the calibration coefficients for the X coordinate. To obtain the X coordinate, the first
value is multiplied by the X sample, the second value by the Y sample, and the third value added with the products.
Bit
15
14
Field
13
12
11
10
9
8
7
6
5
XCALxMSB
3
2
1
0
XCALxLSB
Signal
Description
15–8
XCALxMSB
Most significant byte for the X coordinate calibration value.
7–0
XCALxLSB
Least significant byte for the X coordinate calibration value.
4.2.4.2
4
Y calibration values
This set of three 16-bit values represents the calibration coefficients for the Y coordinate. To obtain the Y coordinate, the first
value is multiplied by the X sample, the second value by the Y sample and the third value added with the products.
Bit
15
Field
14
13
12
11
10
9
8
7
XCALxMSB
Signal
6
5
4
3
2
1
0
XCALxLSB
Description
15–8
YCALxMSB
Most significant byte for theY coordinate calibration value.
7–0
YCALxLSB
Least significant byte for the Y coordinate calibration value.
CRTouch Data Sheet, Rev. 3
50
Freescale Semiconductor
Memory Map and Registers Description
4.2.4.3
X and Y two touch constant values
These values are used for calculations on two touch gestures.
Bit
15
14
Field
13
12
11
10
9
8
7
6
5
4
X/YCONSTMSB
Signal
3
2
1
0
X/YCONSTLSB
Description
15–8
Most significant byte for the X/Y two touch constant calibration value.
X/YCONSTMSB
7–0
Least significant byte for the X/Y two touch constant calibration value.
X/YCONSTLSB
4.2.5
4.2.5.1
Bit
Field
TSS Configuration registers
Capacitive system configuration
7
6
Reserved
5
4
3
2
DCTRACKEREN
STUCKKEYEN
Reserved
CLPEN
Signal
7–6
Reserved
5
DCTRACKEREN
4
STUCKKEYEN
3
Reserved
2
CLPEN
1–0
Reserved
1
0
Reserved
Description
Reserved
DC Tracker Enable — This bit enables the DC tracker to continuously adjust the
electrode capacitance baseline. The periodicity at which the baseline is adjusted is
determined by the DC Tracker Rate.
Stuck Key Enable — This bit enables the baseline recalibration of a touched electrode
after a period of time. If the electrode remains touched for as long as the Stuck Key
Timeout register defines, then the electrode baseline is recalculated and as a
consequence the electrode is released.
Reserved
Capacitive Low Power Enable — This bit enables one of the four electrodes to wake the
system from Shutdown mode. When this bit is enabled, no electrodes are scanned while
in Run mode. This bit should be enabled only prior to entering into Shutdown mode. This
bit is not restored and will always be 0 after a reset.
Reserved
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
51
Memory Map and Registers Description
4.2.5.2
DC Tracker Rate
Bit
7
6
5
4
3
2
1
0
DCTRACKERRATE
Field
Signal
Description
7–0
DCTRACKERRATE
Determines how often the recalibration function occurs. This number represents the number of
capacitive samples required before recalibration. If this register is set to 0, the DC Tracker
feature is disabled.
0 DC Tracker feature disabled
1–255 DC Tracker executed every n sampling period
4.2.5.3
Response Time register
Bit
7
6
Field
Reserved
5
4
2
1
0
RESPTIME
Signal
Description
7–6
Reserved
Reserved
5–0
RESPTIME
4.2.5.4
3
Determines the number of measurements required to detect a status change in any electrode.
This value represents the number of capacitive samples required for an electrode status
change detection.
1–32 n measurements to be used
Stuck Key Timeout register
Bit
7
6
5
4
3
2
1
0
STUCKKEYTOUT
Field
Signal
Description
7–0
STUCKKEYTOUT
Determines how many mili-seconds must an electrode be detected as touched before
recalibrating that electrode and then detect it as untouched. If this value is set to 0, the stuck
key feature is disabled.
0 Stuck key feature disabled
1–255 Electrode recalibrated after n task executions
CRTouch Data Sheet, Rev. 3
52
Freescale Semiconductor
Memory Map and Registers Description
4.2.5.5
Electrodes Sensitivity
This set of registers, one per electrode, holds the sensitivity value of each electrode. Sensitivity value is an 8-bit value that
represents the minimum difference between an instant reading versus the baseline required to indicate a touch.
Bit
7
Field
6
5
4
Reserved
3
2
1
0
ExSENS
Signal
Description
7
Reserved
6–0
ExSENS
4.2.5.6
Represents the capacitance threshold for an electrode to be detected as touched, relative to
the baseline value of that electrode.
2–127 Electrode x (0 to 3) sensitivity
Electrodes enablers
This register holds the information of which electrode is enabled. Each bit represents an electrode
Bit
7
6
Field
5
4
Reserved
Signal
2
1
0
E3EN
E2EN
E1EN
E0EN
Description
3–0
ExEN
4.2.5.7
3
1 – Electrode x Enabled
0 – Electrode x Disabled
Low Power Scan Period register
Represents the value of the scan period in the low power mode, this range does not represent a linear (ms) scan interval.
Bit
Field
7
6
5
4
3
Reserved
2
1
0
LPSP
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
53
Memory Map and Registers Description
Signal
Description
7–4
Reserved
Reserved
LPSP
4.2.5.8
Determines scan period in low power mode. Only selection from the list of predefined values is
allowed.
0000 — 1 ms scan interval
0001 — 5 ms scan interval
0010 — 10 ms scan interval
0011 — 15 ms scan interval
0100 — 20 ms scan interval
0101 — 30 ms scan interval
0110 — 40 ms scan interval
0111 — 50 ms scan interval
1000 — 75 ms scan interval
1001 — 100 ms scan interval
1010 — 125 ms scan interval
1011 — 150 ms scan interval
1100 — 200 ms scan interval
1101 — 300 ms scan interval
1110 — 400 ms scan interval
1111 — 500 ms scan interval
Low Power Electrodes register
This register represents the number of the electrodes scanned in the low power mode.
Bit
7
6
5
Field
4
0
LPEL
Reserved
1–0
LPEL
Field
1
Description
7–2
Reserved
Bit
2
Reserved
Signal
4.2.5.9
3
Low Power Electrode — This value selects which of the four electrodes, from E0 – E3, will be
scanned when the system is in Shutdown mode and the CLPEN bit is enabled in the Capacitive
System Configuration register.
Low Power Electrode Sensitivity register
7
Reserved
6
5
4
3
2
1
0
LPSENS
CRTouch Data Sheet, Rev. 3
54
Freescale Semiconductor
Memory Map and Registers Description
Signal
Description
7
Reserved
6–0
LPSENS
4.2.5.10
Determines the sensibility value for the low power electrode.
Capacitive Resolution register
This register determines the resolution of the capacitive samples. Increasing the capacitive resolution helps improving the signal
to noise ratio when using thick dielectrics. A reset is needed for this value to take effect.
Bit
7
6
Field
5
4
3
2
Reserved
0
CAPRES
Signal
Description
7–4
Reserved
Reserved
3–0
CAPRES
Resolution of capacitive samples.
0–7 Reserved
8–11 Resolution value
12–15 Reserved
4.2.5.11
1
Capacitive Events register
This register is used to configure events for keypad, rotary and slider controls. Each bit has a different meaning if the enabled
control is a keypad, rotary, or slider.
Bit
7
Field
6
Reserved
5
4
3
2
1
0
RELEN
AUTOREPEN
HLDEN
MOVEN
TOUCHEN
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
55
Memory Map and Registers Description
Signal
Description
7-5
Reserved
Reserved
4
RELEN
Release Event Enabler
If this bit is set, the Capacitive Event bit in the Status Register 2 is set when all the electrodes
in the control are released.
1 Event enabled
0 Event disabled
3
AUTOREPEN
Auto Repeat Enable
If this bit is set, the Capacitive Event bit in the Status Register 2 will be set at the rate defined
by the Auto Repeat Rate register when the same electrode remains touched.
1 Auto-repeat enabled
0 Auto-repeat disabled
2
HLDEN
Hold event enabler
If this bit is set, the Capacitive Event bit in the Status Register 2 will be set when an electrode
is first touched and remains touched for the period of time defined by the Auto Repeat Start
register. The hold event is produced only once, and auto repeat events may be produced after.
1 Hold event enabled
0 Hold event disabled
1
MOVEN
Movement event enabler
If this bit is set, the Capacitive Event bit in the Status Register 2 will be set when a transition
from one position to another is detected.
1 Movement event enabled
0 Movement event disabled
0
TOUCHEN
Touch event enabler
If this bit is set, the Capacitive Event bit in the Status Register 2 will be set when all electrodes
are released and an initial touch is detected in any of the electrodes.
1 Touch event enabled
0 Touch event disabled
Keypad Events
Bit
Field
7
6
5
MAXKEYS BUFFOV Reserved
4
3
2
1
0
KEYEXEN
BUFFOVEN
AUTOREPEN
RELEN
TOUCHEN
CRTouch Data Sheet, Rev. 3
56
Freescale Semiconductor
Memory Map and Registers Description
Signal
Description
7
MAXKEYS
This bit reflects if the number of keys allowed to be touched at the same time through the Max
Keys register has been exceeded. This bit is automatically cleared when the condition is no
longer true.
1 Number of key is exceeded
0 Number of keys below the configured value
6
BUFFOV
This bit reflects if the Keypad FIFO is full. This bit is automatically cleared with a read of the
register.
1 Keypad FIFO holds 16 events
0 Keypad FIFO has free elements
5
Reserved
Reserved
4
KEYEXEN
If this bit is set, the Capacitive Event bit in the Status Register 2 Is set when the MAXKEYS flag
is set.
1 Keys exceeded event enabled
0 Keys exceeded event disabled
3
BUFFOVEN
If this bit is set, the Capacitive Event bit in the Status Register 2 Is set when the BUFFOV flag
is set.
1 Buffer overflow event enabled
0 Buffer overflow event disabled
2
AUTOREPEN
If this bit is set, the new touch events are stored in the Keypad FIFO at the rate defined by the
AUTORPRATE register while the electrode remains touched.
1 Touch event auto repeat enabled.
0 Touch event auto repeat disabled.
1
RELEN
If this bit is set, electrode release events are stored in the Keypad FIFO.
1 Release events stored in FIFO
0 Release events not stored in FIFO
0
TOUCHEN
4.2.5.12
If this bit is set, electrode touch events are stored in the Keypad FIFO.
1 Touch events stored in FIFO
0 Touch events not stored in FIFO
Auto repeat rate register
Bit
7
Field
6
5
4
3
2
1
0
AUTORPRATE
Signal
Description
7–0
AUTORPRATE
Auto repeat rate — Sets the rate at which the pressed keys are reported when kept pressed. If
set to 0, no auto-repeat occurs and the event will be automatically disabled in the Events
Register. The user must manually re-enable this event if desired.
0 Auto-repeat feature disabled
1–255 Touch event reported every n measurements
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
57
Memory Map and Registers Description
4.2.5.13
Auto repeat rate start register
Bit
7
6
5
4
3
Field
2
1
0
AUTORPSTRT
Signal
Description
7–0
AUTORPSTRT
Auto repeat start
Sets the time a key must remain pressed before generating new events at the auto-repeat rate.
If set to 0, the auto-repeat state will be entered immediately after the last touch.
0–255 Wait n measurements before auto-repeat.
4.2.5.14
Max Touches register
This register defines the maximum number of simultaneous touched keys reported by a keypad control. This feature can be used
to control the function when a bigger than expected area is touched. For example, a multiplexed array of electrodes where only
two keys are needed to detect a value or function. In this case, the MaxTouches register is configured with a value of two.
Bit
7
Field
6
5
4
3
2
Reserved
1
0
MAXTOUCHES
Signal
Description
7–0
MAXTOUCHES
Maximum number of touches. Sets the limit for simultaneous touched keys. If set to 0, no limit
is established.
0 No limit established
1–3 Limit set to n keys.
CRTouch Data Sheet, Rev. 3
58
Freescale Semiconductor
Electrical Specifications
Appendix A Electrical Specifications
This chapter contains electrical and timing specifications.
A.1
Voltage and current operating requirements
Symbol
Description
Minimum
Maximum
Unit
VDD
Supply voltage
1.8
3.6
V
VDDA
Analog supply voltage
1.8
3.6
V
VDD-VDDA
VDD to -VDDA differential voltage
-0.1
0.1
Vss-VssA
Vss to -VssA differential voltage
-0.1
0.1
VIH
Input high voltage 1
0.7 X VDD
0.75 X VDD
—
—
V
V
—
—
0.35 X VDD
0.3 X VDD
V
V
0
0
2
–0.2
mA
mA
0
0
25
–5
mA
mA
VDD – 0.5
VDD – 0.5
—
—
V
V
—
—
0.5
0.5
V
V
VIL
•
•
Input low voltage 2
•
•
IIC
2.7 V ≤ VDD ≤ 3.6 V
1.8 V ≤ VDD ≤ 2.7 V
2.7 V ≤ VDD ≤ 3.6 V
1.8 V ≤ VDD ≤ 2.7 V
DC Injection current – single pin 3
•
•
VIN > VDD
VIN < VSS
DC injection current – sum of all stressed pins 3
•
•
VOH
VOL
VIN > VDD
VIN < VSS
Output high voltage
•
•
2.7 V ≤ VDD ≤3.6 V, IOH = –10 mA
1.8 V ≤ VDD ≤ 2.7 V, IOH = –3 mA
Output low voltage
•
•
2.7 V ≤ VDD ≤ 3.6 V, IOH = –10 mA
1.8 V ≤ VDD ≤ 2.7 V, IOH = –3 mA
TJ
Die junction temperature
–40
125
°C
TA
Ambient temperature
–40
105
°C
1.The device always interprets an input as a 1 when the input is greater than or equal to VIH (min.) and less than or equal to VIH
(max.), regardless of whether input hysteresis is turned on.
2. The device always interprets an input as a 0 when the input is less than or equal to VIL (max.) and greater than or equal to VIL
(min.), regardless of whether input hysteresis is turned on.
3. All functional non-supply pins are internally clamped to VSS and VDD. Input must be current limited to the value specified. To
determine the value of the required current-limiting resistor, calculate resistance values for positive and negative clamp
voltages, then use the larger of the two values. Power supply must maintain regulation within operating VDD range during
instantaneous and operating maximum current conditions. If positive injection current (VIn > VDD) is greater than IDD, the
injection current may flow out of VDD and could result in external power supply going out of regulation. Ensure external VDD
load will shunt current greater than the maximum injection current. This will be the greatest risk when the MCU is not
consuming power. Examples are: if no system clock is present, or if clock rate is very low (which reduces overall power
consumption).
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
59
Electrical Specifications
A.2
UART timing specifications
Description
A.3
Min
Typical
Max
Unit
Reading response time
—
57
75
S
Writing response time
—
81
110
S
Auto baudrate pulse width
1.5
—
—
ms
Time between auto baudrate pulse and 2
first synchronization byte
—
—
ms
Auto baudrate timeout
—
1.1
s
—
ESD handling ratings
Symbol
Description
Min.
Max.
Unit
Notes
VHBM
Electrostatic discharge voltage,
human body model
-2000
+2000
V
1
VCDM
Electrostatic discharge voltage,
charged-device model
-500
+500
V
2
I
Latch-up current at ambient
temperature of 105°C
-100
+100
mA
1. Determined according to JEDEC Standard JESD22-A114, Electrostatic Discharge (ESD) Sensitivity Testing Human Body Model
(HBM).
2. Determined according to JEDEC Standard JESD22-C101, Field-Induced Charged-Device Model Test Method for
Electrostatic-Discharge-Withstand Thresholds of Microelectronic Components.
A.4
I2C timing specifications
Description
A.5
Min
Max
Unit
Reading frame duration
214
1700
S
Writing frame duration
300
1800
S
Capacitive electrodes specifications
Description
Electrode capacitance range
Min
1
Capacitive electrodes sampling peroid —
Typical
Max
Unit
20
500
pF
7
—
mS
CRTouch Data Sheet, Rev. 3
60
Freescale Semiconductor
Electrical Specifications
A.6
Current ratings
Typical1
Description
Max2
Unit
Run
mA
•
•
3.3 V
1.8 V
11.8
11.8
14.6
13.7
3.3 V
1.8 V
0.39
0.39
6.9
6.1
1
1
120
61
Sleep
•
•
mA
A
Shutdown
•
•
3.3 V
1.8 V
1. Average current measured with the device in idle state.
2. Average current measured while touching the touch screen, with pressure and two touch gestures enabled. A screen with
impedances around 600 was used. This value varies depending on the current consumed by the screen when touched.
A.7
Operating mode transition timing specification
Description
Min
Max
Unit
Reset – Run1
—
13
mS
Run – Sutdown transiton
22
5503
S
Sleep – Run4
5
—
S
Wake pulse
10
—
S
1. Valid for power on reset, pin reset and shutdown wakeup.
2. Measured when only the shutdown bit is written without prior register writes.
3. Measured after writing a series of registers before shutdown. Time increases due to the time required to store values in non
volatile memory.
4. After a falling edge on Wake pin.
A.8
Resistive screen scan times specifications
Description
Signal settling time
Min
Typical
Max
14
100
300
—
—
150
160
—
—
Normal mode
Calibration mode
S
S
Signal measurement time
•
•
Unit
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
61
Electrical Specifications
A.9
NVM reliability specifications
Symbol
Description
Min
Typical
Unit
tnvmretee100
Data retention up to 100% of write
endurance
5
50
Years
tnvmretee10
Data retention up to 10% of write
endurance
10
100
Years
tnvmretee1
Data retention up to 1% of write
endurance
15
100
Years
nnvmwree
Write Endurance
315 K
1.6 M
Writes
CRTouch Data Sheet, Rev. 3
62
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Appendix B Packing Information
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Packing Information
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CRTouch Data Sheet, Rev. 3
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Packing Information
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Packing Information
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Document Number: CRTOUCHDS
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