Atmel QTouch
AT08774: SAM D20 PTC with I2C Slave
APPLICATION NOTE
Introduction
®
This application note explains the firmware solution implemented on Atmel
®
®
ATSAMD20J18 device using ARM Cortex -M0+ processor. The firmware
solution demonstrates SAM D20 PTC self and mutual-capacitance sensor
measurements and transmit/receive touch data using I2C slave.
This implementation is useful in applications where the Host MCU need to
control various touch setup parameters over I2C. For instance, applications
that target low power consumption can adjust clock prescaler and scan
interval. Applications that target best noise performance can adjust noise
counter options dynamically.
The firmware solution is implemented using two SAM D20 Xplained Pro
boards, one acting as User board and the other for QDebug which streams
®
touch data to QTouch Analyzer.
The demonstration program is implemented in C and supports GCC
Compiler used by Atmel Studio 7.
Features
•
•
•
•
•
•
•
Host MCU based touch parameter control
I2C in slave mode
Hardware Touch Acquisition using PTC
Demonstration Program
Uses I2C driver in ASF
QTouch Composer generated touch project
Utilizes SAM D20 Xplained Pro
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
Table of Contents
Introduction......................................................................................................................1
Features.......................................................................................................................... 1
1. Abbreviations and Definitions.................................................................................... 4
2. Overview....................................................................................................................5
3. Hardware and Functional...........................................................................................6
3.1.
3.2.
3.3.
3.4.
3.5.
3.6.
3.7.
Hardware Requisites.................................................................................................................... 6
Circuit Configuration.....................................................................................................................6
Test Setup.....................................................................................................................................7
Startup/Calibration Times............................................................................................................. 8
Calibration.................................................................................................................................... 8
Sleep............................................................................................................................................ 8
Touch Data Debug........................................................................................................................8
4. I2C Operation.......................................................................................................... 10
4.1.
4.2.
I2C-Compatible Address............................................................................................................ 10
CHANGE Pin..............................................................................................................................10
5. Firmware.................................................................................................................. 11
5.1.
5.2.
5.3.
5.4.
5.5.
5.6.
Application Flow..........................................................................................................................11
Creating Self/Mutual Combined Project......................................................................................11
Adding ASF Component (SERCOM I2C - Slave Mode Driver).................................................. 15
Configure and Process I2C........................................................................................................ 16
Files............................................................................................................................................17
Functions....................................................................................................................................18
6. Communication Protocol..........................................................................................21
6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
Introduction.................................................................................................................................21
Address 0: Chip ID..................................................................................................................... 24
Address 1: Major/Minor Code Version........................................................................................24
Address 2: SelfCap Sensor Status.............................................................................................24
Address 3: MutualCap Sensor Status........................................................................................ 24
Address 4: Rotor/Slider Position.................................................................................................24
6.7.
6.8.
6.9.
6.10.
6.11.
6.12.
6.13.
6.14.
6.15.
6.16.
Address 6: Calibrate...................................................................................................................25
Address 7: Reset........................................................................................................................25
Address 8: Scan Interval............................................................................................................ 25
Address 10-11, 52-55: GAIN...................................................................................................... 25
Address 12, 64: Frequency Mode.............................................................................................. 26
Address 13-14, 65-68: PTC Prescaler........................................................................................26
Address 15-16, 69-72: Series Resistor...................................................................................... 27
Address 17-18, 73-76: PTC Prescaler – CC Cal........................................................................27
Address 16, 60: Series Resistor – CC Cal................................................................................. 27
Address 21-23, 81-83: Frequency Hops.................................................................................... 27
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
2
6.17. Address 24-25, 84-87: Filter Level............................................................................................. 28
6.18.
6.19.
6.20.
6.21.
6.22.
6.23.
6.24.
6.25.
6.26.
6.27.
6.28.
6.29.
6.30.
6.31.
6.32.
6.33.
6.34.
6.35.
6.36.
6.37.
6.38.
6.39.
6.40.
6.41.
6.42.
6.43.
6.44.
6.45.
Address 26-27, 88-91: Auto OS................................................................................................. 28
Address 28, 92: Auto Tune.........................................................................................................29
Address 29-30, 93: AKS.............................................................................................................29
Address 31-32, 94: Detect Threshold.........................................................................................30
Address 33-34, 95: Detect Hysteresis........................................................................................30
Address 35-36, 96: Position Resolution..................................................................................... 30
Address 97: Position Hysteresis.................................................................................................31
Address 37, 99: Detect Integration.............................................................................................31
Address 38, 100: Away From Touch Drift (Positive Drift)........................................................... 32
Address 39, 101: Towards Touch Drift (Negative Drift).............................................................. 32
Address 40, 102: Max On Duration............................................................................................ 33
Address 41, 103: Drift Hold Time............................................................................................... 33
Address 42, 104: Away from Touch Recalibration Delay............................................................33
Address 43, 105: Calibration Burst Count - Seq1...................................................................... 34
Address 44, 106: Calibration Burst Count - Seq2...................................................................... 34
Address 45, 107: Recalibration Threshold................................................................................. 34
Address 46-47,108-109: Sensor Post-processing Mode............................................................35
Address 48-49, 110-111: Auto OS Signal Stability Limit.............................................................35
Address 50-51,112-113: Frequency Auto Tune Stability Limit....................................................35
Address 52,114: Frequency Auto Tune In Counter.................................................................... 36
Address 54-55,116-117: Noise Measurement Signal Stability Limit .......................................... 36
Address 56,118: Noise Measurement Noise Limit......................................................................36
Address 57,119: Noise Measurement Sensor Lockout Setting.................................................. 37
Address 58,120: Noise Measurement Lockout Count Down......................................................37
Address 122 – 125: SelfCap Signal........................................................................................... 37
Address 126 – 129: SelfCap Reference.....................................................................................38
Address 130-137: MutualCap Signal..........................................................................................38
Address 138-145: MutualCap Reference................................................................................... 38
7. References.............................................................................................................. 40
8. Revision History.......................................................................................................41
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
3
1.
Abbreviations and Definitions
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Acquisition cycle: A single capacitive measurement process
ASF: Atmel Software Framework
Calibration: Multiple touch measurements carried out continuously to set Reference
Delta: Difference between Reference and Signal (Reference – Signal)
Detect Threshold: Determines delta required for a valid touch
DGI: Data Gateway Interface
EDBG: Embedded Debugger
Drift: AdjustingReference level to track changes in signal level due to environmental changes
I2C: Inter-Integrated Circuit
Max on Duration: Duration for which sensor stays detected
PTC: Peripheral Touch Controller
Reference: Long term average measurement on a channel
Recalibration Threshold: It is the level above which automatic recalibration occurs
Scan Interval: Duration in which touch measurement is performed
SCL: Serial Clock Line
SDA: Serial Data Line
SERCOM: Serial Communication Module
Signal: Raw measurement for capacitance change on a channel
X Line: The Sense Line connected to the X Electrode in Mutual capacitance method
Y Line: The Sense Line connected to the Y Electrode used in Self-capacitance method
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
4
2.
Overview
The SAM D20 series device is a 32-bit ARM Cortex-M0+ based microcontroller, which supports hardware
touch acquisition using PTC peripheral. PTC supports capacitive touch sensing on both self and mutual
capacitance sensors, without any external components (Series resistors might be required to handle
extreme noise scenarios). Refer PTC User guide for detailed information on PTC and QTouch Library.
The firmware solution demonstrated in this application note uses two self-capacitance button sensors and
one mutual capacitance slider sensor. This solution can be easily scaled to support various sensor
configuration with appropriate modifications in firmware.
The device series provides up to six SERCOMs that can be configured to operate as an I2C, SPI, and
USART interface. The firmware solution configures SERCOM4 (PA12, PA13) of ATSAMD20J18 device as
I2C communication interface in slave mode.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
5
3.
3.1.
Hardware and Functional
Hardware Requisites
The following table lists the hardware required to build the test setup for analyzing this firmware solution.
Table 3-1. Hardware Requisites
3.2.
Hardware
Quantity
SAM D20 Xplained Pro board
2
QT1 QTouch Self-capacitance sensor board
1
QT1 QTouch Mutual capacitance sensor board
1
STK600
1
STK600 – ATMEGA2560 board
1
Circuit Configuration
The following table shows connections used in this firmware solution.
Table 3-2. Sensor Pin Configuration used in SAM D20 User Board
SAM D20 Xplained Pro (User Board)
QT1 Xplained Pro Sensor Board
PA02 (Y0)
Self-capacitance Button_0 (Y_8)
PA03 (Y1)
Self-capacitance Button_1 (Y_7)
PA10 (X2)
Mutual capacitance Slider Channel_0 (X_1)
PA11 (X3)
Mutual capacitance Slider Channel_1 (X_2)
PA20 (X8)
Mutual capacitance Slider Channel_2 (X_3)
PA21 (X9)
Mutual capacitance Slider Channel_3 (X_4)
PB06 (Y12)
Mutual capacitance Slider (Y_S)
Note: The sense line (X / Y) numbers specified in table preceeding table under SAM D20 Xplained Pro
board are as based on the information in the SAM D20 Datasheet. The X / Y numbers specified under
QT1 sensor board are generic (as marked in QT1 sensor boards).
Table 3-3. Connection between SAM D20 User Board and AVR3009 Host Microcontroller
SAM D20 Xplained Pro (User Board)
AVR3009 Host (ATmega2560)
PA12 (SDA)
PD1
PA13 (SCL)
PD0
PA27 (CHANGE pin)
PD2
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
6
Table 3-4. Connection between SAM D20 User Board and SAM D20 Xplained Pro for QDebug
SAM D20 Xplained Pro (User Board)
SAM D20 Xplained Pro (QDebug)
PA17 (SS) - Connect to GND
-
PA18 (MOSI)
PB22
PA16 (MISO)
PB16
PA19 (SCK)
PB23
GND
GND
Figure 3-1. Circuit Configuration
The firmware solution provided is applicable for ATSAMD20J18 device operating as I2C Slave.
Firmware validation uses the demonstration code provided with the application note “AVR3009: Driving
QTouch Device with IIC Interface” with the required modifications.
An external pull-up resistor of 10kΩ is required on CHANGE line and 4.7kΩ is required on SCL and SDA
lines. Using external pull-up resistor of 10kΩ on RESET line is optional, as the device features an internal
pull-up resistor on this pin.
3.3.
Test Setup
Table 3-2 Sensor Pin Configuration used in SAM D20 User Board represents the actual test setup used
for the firmware validation.
This setup uses one SAM D20 Xplained Pro board, which acts as user board and the same board is used
for QDebug. This Xplained Pro board is directly connected to QT1 Mutual capacitance sensor board
(slider sensor) and hooked wires for connecting to QT1 Self-capacitance sensor board (button sensor). To
demonstrate the firmware solution, the interconnection between Master and Slave uses wires as shown in
the following image:.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
7
Figure 3-2. Test Setup
3.4.
Startup/Calibration Times
The device requires an initialization time of approximately 300ms. This includes calibration time of around
200ms. Any subsequent recalibration will also take approximately 200ms.
The CHANGE line is asserted at startup, after initialization.
3.5.
Calibration
The calibration does not occur periodically. Keys are calibrated when one of the following conditions
occur:
•
•
•
•
Power up
Sensor signal value is greater than the Positive Recalibration Threshold
– Default = 50% of Detect Threshold
At the end of Max on Duration (if enabled)
– Default = Disabled
Host MCU issues a Calibrate Command
If any sensor was in detect state before recalibration, it will go out of detect after recalibration. This will
change the Status Bytes and trigger the CHANGE line to go low.
3.6.
Sleep
The default scan interval of the device is set as 20ms. In the firmware solution touch measurement is
performed on the configured sensors. To reduce power consumption, CPU sleeps during touch
acquisition as well as for the remaining period of scan interval.
3.7.
Touch Data Debug
The SAM D20 Xplained Pro contains Embedded Debugger (EDBG) that features an Atmel Data Gateway
Interface (DGI) using SPI and I2C. The DGI can be used to transmit a variety of data from the Xplained
Pro kit to the host PC. This arrangement can be used to send QDebug data from a user board to PC
running QTouch Analyzer for touch sensor data analysis and tuning. The example project generated
using QTouch composer transfers QDebug data over SPI.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
8
To stream QDebug data from the user board (SAM D20 Xplained Pro) using another SAM D20 Xplained
Pro board, refer Table 3-4 Connection between SAM D20 User Board and SAM D20 Xplained Pro for
QDebug for connection details and refer to procedure provided in PTC User Guide.
The same user board SAM D20 Xplained Pro board can also be used to stream QDebug data for testing
the firmware solution provided. Required SPI debug line connections to EDBG is hard wired in SAM D20
Xplained Pro board. So, using the corresponding debug related pin definitions in touch.h file as shown
in the following table is sufficient to enable QDebug in the same Xplained Pro board.
Table 3-5. Using the Same SAM D20 (User Board) Xplained Pro for QDebug
SAM D20 Xplained Pro (User Board)
Pin
Function
PB22
MOSI
PB16
MISO
PB23
SCK
PB31
SS
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
9
4.
I2C Operation
The firmware solution use SERCOM I2C interface to communicate with Master MCU. This Atmel Twowire Serial Interface is compatible with Philips I2C Bus/Protocol.
Refer to ATSAMD20J18 device datasheet for details of operation.
4.1.
I2C-Compatible Address
The I2C address for the slave ATSAMD20J18 device is set as 0x12.
4.2.
CHANGE Pin
The CHANGE pin is an active low open drain output that can be used to alert the host about any change
in any of the sensor status, thus reducing the need for wasteful I2C communications. CHANGE pin goes
low when there is change in status bytes of any sensor or slider position values (Memory map address 2
to 4, detailed in Table 6-1 Memory Map). When the master performs a read from all the status bytes,
CHANGE pin becomes high.
Poll rate: The host can make use of CHANGE pin output to initiate a communication; this will guarantee
the optimal polling rate.
If the host cannot make use of CHANGE pin, the poll rate should be no faster than once per acquisition
cycle. The default scan interval is 20ms. A faster scan interval will not provide new information and will
slow down the chip operation.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
10
5.
Firmware
5.1.
Application Flow
5.2.
Creating Self/Mutual Combined Project
The following procedure explains creating a combined project for both self and mutual capacitance
sensors.
5.2.1.
Create Self-capacitance Project
Use QTouch Composer – Project builder wizard and create self-capacitance project for two button
sensors as per configuration in the following table, with QDebug enabled. This project name is referred as
“selfcap” in the following sections.
Table 5-1. Self-capacitance Sensor Pin Configuration used in SAM D20 User Board
Parameter Sense
pin
Button0
Y0
(PA02)
Gain Detect
threshold
Filter
level
Auto
oversampling
Auto
tuning
Series
resistor
Frequency
mode
1
8
Disable
PRSC
100K
None
30
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
11
Table 5-2. Debug Pin Configuration used in SAM D20 User Board
Parameter
ATSAMD20J18 port pin
SPI_BB_SS
PA17
SPI_BB_SCK
PA19
SPI_BB_MOSI
PA18
SPI_BB_MISO
PA16
Y lines used in this project are custom configuration, based on available unused pins in the SAM D20
Xplained Pro board. Note that the Y lines are not the same as used in standard ASF example project
“SAM D20 Xplained Pro and QT1 Xplained Pro Self-capacitance example application”.
5.2.2.
Create Mutual capacitance Project
Use QTouch Composer Project builder wizard and create mutual capacitance project for one slider sensor
as per configuration in the following table, with QDebug disabled. This project name is referred as
“mutualcap” in the following sections.
Table 5-3. Mutual Capacitance Sensor Pin Configuration used in SAM D20 User Board
Parameter X Line Y Line
5.2.3.
Gain Detect
Filter Auto
Auto
Series Frequency
threshold level oversampling tuning resistor mode
Slider
Channel0
X2
Y12
1
(PA10) (PB06)
Slider
Channel1
X3
Y12
1
(PA11) (PB06)
Slider
Channel2
X8
Y12
1
(PA20) (PB06)
Slider
Channel3
X9
Y12
1
(PA21) (PB06)
30
8
Disable
PRSC
100K
None
Create Combined (Self + Mutual capacitance) Project
The self-capacitance project created is set as base application project and the mutual capacitance project
created is used as reference. Append the required contents from mutual capacitance to self-capacitance
project, for enabling touch measurement on both self and mutual capacitance sensors.
The following procedure details the steps to include required contents. Use the demonstration project
available for reference.
1. Copy all the macros (excluding DEF_TOUCH_PTC_ISR_LVL) from the touch.h file in the
mutualcap project and paste in the touch.h file from the selfcap project.
2.
Compare both touch.c files, copy the required contents from the mutual capacitance project and
perform the following changes in the selfcap base project.
2.1.
Declare the data block array for the mutual capacitance method, after the self-capacitance
data array declaration.
/** * Mutual Cap Data block provided as input to
Touch library. */static uint8_t
mutlcap_data_blk[PRIV_MUTLCAP_DATA_BLK_SIZE];
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
12
2.2.
Declare mutual capacitance sensors pin information, along with the self-capacitance
sensor details.
/**
* Mutual Cap Sensor Pins Info.
*/
uint16_t mutlcap_xy_nodes[DEF_MUTLCAP_NUM_CHANNELS * 2] = {DEF_MUTLCAP_NODES};
filter_level_t mutlcap_filter_level_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_FILTER_LEVEL_PER_NODE};
uint8_t mutlcap_auto_os_per_node[DEF_MUTLCAP_NUM_CHANNELS]=
{DEF_MUTLCAP_AUTO_OS_PER_NODE};
gain_t mutlcap_gain_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_GAIN_PER_NODE};
rsel_val_t mutlcap_resistor_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_SENSE_RESISTOR_PER_NODE };
prsc_div_sel_t mutlcap_prsc_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_CLK_PRESCALE_PER_NODE };
prsc_div_sel_t mutlcap_boot_prsc_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_CC_CAL_CLK_PRESCALE_PER_NODE};
rsel_val_t mutlcap_boot_resistor_per_node[DEF_MUTLCAP_NUM_CHANNELS] =
{DEF_MUTLCAP_CC_CAL_SENSE_RESISTOR_PER_NODE};
freq_hop_sel_t mutlcap_freq_hops[3u] = {DEF_MUTLCAP_HOP_FREQS};
2.3.
2.4.
Define Configuration structure for mutual capacitance after self-capacitance structure.
Update the touch_config structure with the address of mutual capacitance configuration
parameter, as shown in following code snippet.
touch_config_t touch_config = {
&mutlcap_config,
&selfcap_config,
/* Pointer to Self Cap configuration structure.*/
DEF_TOUCH_PTC_ISR_LVL,
/* PTC interrupt level. */
};
2.5.
Define the measure complete callback prototype, after self cap measure complete callback
routine.
void touch_mutlcap_measure_complete_callback( void );
2.6.
3.
Similar to measure complete callback function for self-capacitance, define the mutual
capacitance measure complete call back function in the end of touch.c file.
To invoke the mutual capacitance measurement related APIs as follows. Use the mutual
capacitance project touch.c file as reference.
3.1.
Invoke touch_mutlcap_sensors_init API after invoking
touch_selfcap_sensors_init.
touch_ret = touch_mutlcap_sensors_init(&touch_config);
if (touch_ret != TOUCH_SUCCESS) {
touch_app_err_handler(TOUCH_INIT_CONFIG_ERR, touch_ret);
}
3.2.
Similarly invoke touch_mutlcap_sensors_calibrate after invoking
touch_selfcap_sensors_calibrate.
touch_ret = touch_mutlcap_sensors_calibrate(DEF_MUTL_AUTO_TUNE_VALUE);
if (touch_ret != TOUCH_SUCCESS) {
touch_app_err_handler(TOUCH_INIT_CALIB_ERR, touch_ret);
}
return (touch_ret);
3.3.
Next, configure the mutual capacitance sensors in the touch_sensors_config routine
definition. Append the mutual capacitance sensor configuration next to the self-capacitance
sensors.
touch_ret_t touch_sensors_config(void)
{
touch_ret_t touch_ret = TOUCH_SUCCESS;
sensor_id_t sensor_id;
touch_ret = touch_selfcap_sensor_config(SENSOR_TYPE_KEY,
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
13
CHANNEL_0,CHANNEL_0, NO_AKS_GROUP, 15u, HYST_25,RES_8_BIT, &sensor_id);
if (touch_ret != TOUCH_SUCCESS)
{
touch_app_err_handler(TOUCH_SENSOR_CONFIG_ERR, touch_ret);
}
touch_ret = touch_selfcap_sensor_config(SENSOR_TYPE_KEY,
CHANNEL_1,CHANNEL_1, NO_AKS_GROUP, 15u, HYST_25,RES_8_BIT, &sensor_id);
if (touch_ret != TOUCH_SUCCESS)
{
touch_app_err_handler(TOUCH_SENSOR_CONFIG_ERR, touch_ret);
}
touch_ret = touch_mutlcap_sensor_config(SENSOR_TYPE_SLIDER,
CHANNEL_0,CHANNEL_3, NO_AKS_GROUP, 10u, HYST_25,RES_8_BIT, 0u, &sensor_id);
if (touch_ret != TOUCH_SUCCESS)
{
touch_app_err_handler(TOUCH_SENSOR_CONFIG_ERR, touch_ret);
}
}
3.4.
return (touch_ret);
Finally, invoke the mutual capacitance sensor measure routine next to the self-capacitance
sensor measure routine. The touch acquisition process is sequential in case of SAM D20
PTC. So, before invoking the mutual capacitance sensor acquisition, the application needs
to ensure that the acquisition is complete on the self-capacitance sensors and vice-versa.
The following code snippet shows the conditional implementation required for invoking
touch acquisition.
touch_ret_t touch_sensors_measure(void)
{
touch_ret_t touch_ret = TOUCH_SUCCESS;
if (!(p_selfcap_measure_data->acq_status & TOUCH_CC_CALIB_ERROR))
{
1u)
if (touch_time.time_to_measure_touch == 1u) {
if(start_check == 1 || p_mutlcap_measure_data->measurement_done_touch ==
{
touch_ret = touch_selfcap_sensors_measure(
touch_time.current_time_ms,
NORMAL_ACQ_MODE,
touch_selfcap_measure_complete_callback);
if ((touch_ret != TOUCH_ACQ_INCOMPLETE) &&
(touch_ret == TOUCH_SUCCESS)) {
p_mutlcap_measure_data->measurement_done_touch = 0u;
start_check = 0;
} else if ((touch_ret != TOUCH_SUCCESS) &&
(touch_ret != TOUCH_ACQ_INCOMPLETE)) {
touch_app_err_handler(TOUCH_MEASURE_INCOMPLETE, touch_ret);
/* Reaching this point can be due to *
1. The api has retured an error due to a invalid
* input parameter.
*
2. The api has been called during a invalid Touch
* Library state. */
}
}
}
if(p_selfcap_measure_data->measurement_done_touch == 1u)
{
touch_ret = touch_mutlcap_sensors_measure(
touch_time.current_time_ms,
NORMAL_ACQ_MODE,
touch_mutlcap_measure_complete_callback);
if ((touch_ret != TOUCH_ACQ_INCOMPLETE) &&
(touch_ret == TOUCH_SUCCESS)) {
p_selfcap_measure_data->measurement_done_touch = 0u;
touch_time.time_to_measure_touch = 0u;
} else if ((touch_ret != TOUCH_SUCCESS) &&
(touch_ret != TOUCH_ACQ_INCOMPLETE)) {
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
14
touch_app_err_handler(TOUCH_MEASURE_INCOMPLETE, touch_ret);
/* Reaching this point can be due to *
1. The api has retured an error due to a invalid
* input parameter.
*
2. The api has been called during a invalid Touch
* Library state. */
}
}
}
else
{
/*
To find which sensor failed in the calibration, check
p_xxxxcap_measure_data->p_sensors[<sensor>].state ==
SENSOR_CALIBRATION_ERROR
*/
touch_app_err_handler(TOUCH_MEASURE_CC_CAL_FAILED, touch_ret);
}
}
return (touch_ret);
Note: In the above code, the start_check variable is used to invoke touch acquisition at
power up. This should be initialized to "1" in touch.c file (uint8_t start_check =
1u;).
Build and Test:The project creation, which can perform measurement on both self and mutual
capacitance sensors is complete. Build the project at this stage and ensure there are no errors /
warnings. Then download it into the ATSAMD20J18 device in SAM D20 Xplained Pro user board.
QDebug:The combined project has QDebug enabled for self-capacitance sensors. So, the performance
of self-capacitance sensors can be analyzed using QTouch Analyzer.
To enable QDebug for the mutual capacitance sensor, enable the required macro definition in the
touch.h file as follows.
//#define DEF_TOUCH_QDEBUG_ENABLE_SELFCAP
#define DEF_TOUCH_QDEBUG_ENABLE_MUTLCAP
#define DEF_TOUCH_QDEBUG_ENABLE 1u
Build and load the project again. Now, mutual capacitance slider performance can be analyzed in QTouch
Analyzer.
Note: The QTouch Analyzer can only provide either self or mutual capacitance sensor data,
simultaneously.
5.3.
Adding ASF Component (SERCOM I2C - Slave Mode Driver)
Next step is to add SERCOM I2C – Slave Mode Callback driver from ASF, into the combined project
created. To open the ASF wizard in the project, click on ASF -> ASF Wizard. Then search and select
SERCOM I2C – Slave Mode I2C driver (Callback) under the Available Modules. Click on the Add
button as shown in the following figure.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
15
Figure 5-1. Selecting SERCOM I2C Slave Driver from ASF
The SERCOM I2C driver is available under the Selected Modules list. Click on the Apply button to
include the selected I2C diver module into the combined project. Save the changes and perform a test
build using the project.
Figure 5-2. Adding SERCOM I2C Slave Driver into the Project
5.4.
Configure and Process I2C
In the user project (combined project created) which includes required I2C drivers from ASF, I2C should
be configured in slave mode and the necessary callbacks should be defined.
The I2C driver added from ASF does not handle internal memory addressing. So the application code
needs to process the read and write commands appropriately.
In the user project, include the source and header files available in the apps_src folder in the
demonstration project. Among the included source files, i2c_process.c file takes care of configuring
the I2C in slave mode and define I2C callbacks for read request, write request, read complete, write
complete operations.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
16
As well, this file handles internal memory addressing to comply with master requests. This internal
addressing implementation requires number of bytes written by master to the slave device. So, in the
i2c_slave_interrupt.c file in the interrupt handler _i2c_slave_interrupt_handler definition,
a variable for number of bytes written is incremented whenever request is received for write, as shown in
following code snippet.
/* Continue buffer write/read */
} else if (module->buffer_length > 0 && module->buffer_remaining > 0) {
/* Call function based on transfer direction */
if (module->transfer_direction == I2C_TRANSFER_WRITE)
{
_i2c_slave_read(module);
num_bytes_written++;
} else {
_i2c_slave_write(module);
The variable “num_bytes_written” should be declared as extern in the i2c_slave_interrupt.c
file.
extern uint8_t num_bytes_written;
Based on the number of bytes written, the slave decides whether it is a master write instruction or read
instruction.
Case 1: If the number of bytes written is one, then slave determines this as a read request from master.
The data byte received is considered as address to be read and the slave points to that address for read
operation.
Case 2: If the number of bytes written is more than one, then slave determines this as a write request
from master. Slave writes the received data bytes into a data buffer.
Process received data:
During write operation, data bytes written are stored in a data buffer. This data must be processed
appropriately, where the first byte in buffer represents the address to be written into and the following
bytes are the data bytes to be written. These data bytes written updates / configures the touch setup
parameters, discussed in following sections. The i2c_process.c file also handles processing of the
received data bytes and updating the memory map.
To complete configuring and data processing, replace the main.c file available in demonstration project
in the user project. This completes the demonstration project creation by the user.
Build the project and test it using any I2C Master MCU.
5.5.
Files
The folder structure of the firmware solution is as follows:
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
17
Figure 5-3. Folder Structure
The following table provides a brief description of additional files used in this firmware solution.
Table 5-4. File Description
File name
Description
configuration.h Configuration for Change pin is provided here.
5.6.
memorymap.h
Defines memory map structure which contains touch setup parameters as objects.
memorymap.c
Provides a default value to the touch setup parameters in memory map.
i2c_process.h
It consist of function prototypes and macro definitions used in i2c_process.c
i2c_process.c
It configures I2C and processes data bytes received.
Functions
A brief description of functions used in the additional files included in the firmware solution are provided in
the following table.
Table 5-5. Functions
Function
Description
void memorymap_defaults(void)
Provides default values to
touch setup parameters in
memory map.
Input
None
Output
None
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
18
Function
Description
void i2c_read_request_callback(struct
i2c_slave_module *const module)
This function points the
read location to the
appropriate memory map
location requested by
master.
void i2c_write_request_callback(struct
i2c_slave_module *const module)
void i2c_read_complete_callback(struct
i2c_slave_module *const module)
void i2c_write_complete_callback(struct
i2c_slave_module *const module)
void configure_i2c_slave(void)
Input
*const – pointer
to the I2C slave
module
structure.
Output
None
This function points the
write location to the write
buffer.
Input
*const – pointer
to the I2C slave
module
structure.
Output
None
Updates the change pin
status when the status
bytes is read by master.
Input
*const – pointer
to the I2C slave
module
structure.
Output
None
Checks the number of
bytes written and takes
necessary action for read/
write request.
Input
*const – pointer
to the I2C slave
module
structure.
Output
None
Configures SERCOM4
I2C in Slave mode.
Input
None
Output
None
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
19
Function
Description
void configure_i2c_slave_callbacks(void)
Register and enable I2C
Slave callback routines.
void update_sensor_data(void)
void update_setup_config(void)
void update_memory_map(void)
Input
None
Output
None
Updates touch sensor
data measured in the
memory map structure
and updates change pin
status based on sensor
state.
Input
type - type code
for the object
details
requested
Output
None
Updates touch setup
parameters based on
data written by master.
Input
None
Output
None
Updates the memory map
with data written by
master.
Input
None
Output
None
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
20
6.
Communication Protocol
6.1.
Introduction
The device is address mapped. All communications consist of write and read access to the locations in an
8-bit address map.
The memory map structure that contains the touch status / setup parameters used in firmware solution
are provided in the following table. The touch setup parameters can be modified as required for the user
application.
Table 6-1. Memory Map
Address
Use
Access
0
Chip ID
Read
1
Major/Minor Code Version
Read
2
SelfCap Sensor Status
Read
3
MutualCap Sensor Status
Read
4
Rotor/Slider Position
Read
5
Reserved_1
Read
6
Calibrate
Read/Write
7
Reset
Read/Write
8
Scan Interval
Read/Write
9
Reserved_2
Read/Write
10
Gain for Button_0
Read/Write
11
Gain for Button_1
Read/Write
12
Frequency_Mode
Read/Write
13
PTC Prescaler for Channel_0
Read/Write
14
PTC Prescaler for Channel_1
Read/Write
15
Series Resistor for Channel_0
Read/Write
16
Series Resistor for Channel_1
Read/Write
17
PTC Prescaler - CC Cal for Channel_0
Read/Write
18
PTC Prescaler - CC Cal for Channel_1
Read/Write
19
Series Resistor - CC Cal for Channel_0
Read/Write
20
Series Resistor - CC Cal for Channel_1
Read/Write
21 – 23
Frequency Hops
Read/Write
24
Filter Level for Channel_0
Read/Write
Self-capacitance Setup Block
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
21
Address
Use
Access
25
Filter Level for Channel_1
26
Auto OS for Channel_0
27
Auto OS for Channel_1
28
Auto Tune
Read/Write
29 – 30
AKS (Key 0 – 1)
Read/Write
31 – 32
Detect Threshold (Button 0 – 1)
Read/Write
33 – 34
Detect Hysteresis (Button 0 – 1)
Read/Write
35 – 36
Position Resolution (Button 0 – 1)
Read/Write
37
Detect Integration
Read/Write
38
Away From Touch Drift
Read/Write
39
Towards Touch Drift
Read/Write
40
Max On Duration
Read/Write
41
Drift Hold Time
Read/Write
42
Away from touch Recalibration Delay
Read/Write
43
Calibration burst count - Seq1
Read/Write
44
Calibration burst count – Seq2
Read/Write
45
Recalibration Threshold
Read/Write
46 – 47
Sensor post-processing mode
Read/Write
48 – 49
Auto OS signal stability limit
50 – 51
Frequency auto tune stability limit
Read/Write
52
Frequency auto tune In counter
Read/Write
53
Reserved_3
Read/Write
54 – 55
Noise measurement signal stability limit
Read/Write
56
Noise measurement noise limit
Read/Write
57
Noise measurement sensor lockout setting
Read/Write
58
Noise measurement lockout count down
Read/Write
59
Reserved_4
Read/Write
60
Gain for Slider Channel_0
Read/Write
61
Gain for Slider Channel_1
Read/Write
62
Gain for Slider Channel_2
Read/Write
63
Gain for Slider Channel_3
Read/Write
64
Frequency_Mode
Read/Write
Read/Write
Mutual capacitance Setup Block
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
22
Address
Use
Access
65 – 68
PTC Prescaler (Channel_0 to Channel_3)
Read/Write
69 – 72
Series Resistor (Channel_0 to Channel_3)
Read/Write
73 – 76
PTC Prescaler - CC Cal (Channel_0 to Channel_3)
77 – 80
Series Resistor - CC Cal (Channel_0 to Channel_3)
Read/Write
81 – 83
Frequency Hops
Read/Write
84 – 87
Filter Level (Channel_0 to Channel_3)
Read/Write
88 – 91
Auto OS (Channel_0 to Channel_3)
Read/Write
92
Auto Tune
Read/Write
93
Slider AKS
Read/Write
94
Slider Detect Threshold
Read/Write
95
Slider Detect Hysteresis
Read/Write
96
Slider Position Resolution
Read/Write
97
Slider Position Hysteresis
Read/Write
98
Reserved_5
Read/Write
99
Detect Integration
Read/Write
100
Away From Touch Drift
Read/Write
101
Towards Touch Drift
Read/Write
102
Max On Duration
Read/Write
103
Drift Hold Time
Read/Write
104
Away from touch Recalibration Delay
Read/Write
105
Calibration burst count - Seq1
Read/Write
106
Calibration burst count – Seq2
Read/Write
107
Recalibration Threshold
Read/Write
108 – 109
Sensor post-processing mode
Read/Write
110 – 111
Auto OS signal stability limit
Read/Write
112 – 113
Frequency auto tune stability limit
Read/Write
114
Frequency auto tune In counter
Read/Write
115
Reserved_6
Read/Write
116 – 117
Noise measurement signal stability limit
Read/Write
118
Noise measurement noise limit
Read/Write
119
Noise measurement sensor lockout setting
Read/Write
120
Noise measurement lockout count down
Read/Write
121
Reserved_7
Read
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
23
6.2.
Address
Use
Access
122 – 125
SelfCap Signal
Read
126 – 129
SelfCap Reference
Read
130 – 137
MutualCap Signal
Read
138 – 145
MutualCap Reference
Read
Address 0: Chip ID
Address
Bit 7
Bit 6
Bit 5
Bit 4
0
Bit 3
Bit 2
Bit 1
Bit 0
Chip ID
This address holds the Chip ID, always reads 0x1A.
6.3.
Address 1: Major/Minor Code Version
Address
Bit 7
1
Bit 6
Bit 5
Bit 4
Major Version
Bit 3
Bit 2
Bit 1
Bit 0
Minor Version
There is an 8-bit major and minor version of the firmware revision. The top nibble of the firmware version
register contains the major version (1.0) and the bottom nibble contains the minor version (1.0).
6.4.
Address 2: SelfCap Sensor Status
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
2
0
0
0
0
0
0
Button_1
Button_0
The last two bits indicate touch status of two self-capacitance buttons. It is reported as ‘1’ if button is
touched else reports ‘0’ when untouched. A change in this status bits causes CHANGE line to assert low.
6.5.
Address 3: MutualCap Sensor Status
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
3
0
0
0
0
0
0
0
Slider_State
The last bit indicates touch status of mutual capacitance slider. It is reported as ‘1’ if slider is touched else
reports ‘0’ when slider is not in detection. A change in this status bit causes CHANGE line to assert low.
6.6.
Address 4: Rotor/Slider Position
Address
4
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Slider Position
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
24
This byte reports slider position output. This is valid only when slider is in detect state. A change in this
value causes CHANGE line to assert low.
6.7.
Address 6: Calibrate
Address
Bit 7
Bit 6
Bit 5
6
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
CALIBRATE
Writing any non-zero value into this address will trigger the device to start a recalibration on all enabled
sensors.
6.8.
Address 7: Reset
Address
Bit 7
Bit 6
Bit 5
7
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RESET
Any non-zero value will trigger the device to reset. After reset, the device will revert to default settings
provided to touch setup parameters.
The host must wait for at least 300ms for the operation to be completed before communications can be
re-established.
6.9.
Address 8: Scan Interval
Address
Bit 7
Bit 6
Bit 5
8
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SCAN INTERVAL
This 8-bit value represents the duration (in ms) to invoke touch measurement. Longer the interval yields
lower power consumption, as the device sleeps longer after touch measurement, but at the cost of slower
response to touch.
6.10.
Address 10-11, 52-55: GAIN
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
10
GAIN for SelfCap Button_0
11
GAIN for SelfCap Button_1
52
GAIN for MutualCap Slider Channel _0
53
GAIN for MutualCap Slider Channel _1
54
GAIN for MutualCap Slider Channel _2
55
GAIN for MutualCap Slider Channel _3
Bit 1
Bit 0
Address 10-11 represents gain setting for self-capacitance buttons.
Address 52-55 represents gain setting for mutual capacitance slider channels.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
25
Gain setting is applied on a per-channel basis to allow scaling-up of the touch delta upon contact. Gain
setting depends on the sensor design and touch panel thickness.
Range: GAIN_1 to GAIN_32
Default: GAIN_1 ( Self-capacitance), GAIN_2 (Mutual capacitance)
6.11.
Address 12, 64: Frequency Mode
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
12
Frequency Mode for SelfCap
56
Frequency Mode for MutualCap
Bit 1
Bit 0
Address 12 represents frequency mode to be used for self-capacitance buttons.
Address 56 represents frequency mode to be used for mutual capacitance slider.
Frequency mode setting allows users to tune the PTC touch acquisition frequency characteristics to
counter environment noise. The different frequency modes available are:
•
•
•
•
FREQ_MODE_HOP
FREQ_MODE_SPREAD
FREQ_MODE_SPREAD_MEDIAN
FREQ_MODE_NONE
Refer to PTC User guide for more details.
Default: FREQ_MODE_NONE (For both Self-capacitance and Mutual capacitance).
6.12.
Address 13-14, 65-68: PTC Prescaler
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
13 – 16
PTC Prescaler for SelfCap
65 – 68
PTC Prescaler for MutualCap
Bit 1
Bit 0
This setting controls the clock pre-scaler to the Generic clock input to PTC. The Generic clock input to
PTC should be set to 4MHz. The pre-scaler setting scales down the PTC clock as follows:
•
PRSC_DIV_SEL_1 sets PTC Clock to 4MHz
•
PRSC_DIV_SEL_2 sets PTC Clock to 2MHz
•
PRSC_DIV_SEL_4 sets PTC Clock to 1MHz
•
PRSC_DIV_SEL_8 sets PTC Clock to 500kHz
Range: PRSC_DIV_SEL_1 to PRSC_DIV_SEL_8
Default: PRSC_DIV_SEL_1 (For both Self-capacitance and Mutual capacitance)
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
26
6.13.
Address 15-16, 69-72: Series Resistor
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
15 – 16
Series Resistor for SelfCap
77 – 80
Series Resistor for MutualCap
Bit 1
Bit 0
Bit 1
Bit 0
This setting controls the value of internal series resistor on the Y line.
•
RSEL_VAL_0 sets internal series resistor to 0Ω
•
RSEL_VAL_20 sets internal series resistor to 20kΩ
•
RSEL_VAL_50 sets internal series resistor to 50kΩ
•
RSEL_VAL_100 sets internal series resistor to 100kΩ
Range: RSEL_VAL_0 to RSEL_VAL_100
Default: RSEL_VAL_100 (For both Self-capacitance and Mutual capacitance)
6.14.
Address 17-18, 73-76: PTC Prescaler – CC Cal
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
17 – 18
CC Cal PTC Prescaler for SelfCap
73 – 76
CC Cal PTC Prescaler for MutualCap
This setting controls PTC Prescaler to be used during compensation capacitor calibration.
6.15.
Address 16, 60: Series Resistor – CC Cal
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
16
CC Cal Series Resistor for SelfCap
60
CC Cal Series Resistor for MutualCap
Bit 1
Bit 0
This setting controls Series Resistor to be used during compensation capacitor calibration.
6.16.
Address 21-23, 81-83: Frequency Hops
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
21
Frequency Hop_1 for SelfCap
22
Frequency Hop_2 for SelfCap
23
Frequency Hop_3 for SelfCap
81
Frequency Hop_1 for MutualCap
82
Frequency Hop_2 for MutualCap
83
Frequency Hop_3 for MutualCap
Bit 1
Bit 0
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
27
This frequency hop delay setting is used when the Frequency mode is set to FREQ_MODE_HOP.
A set of three frequency hop delay settings should be specified. This delay setting inserts n PTC clock
cycles between consecutive measurements on a given sensor, thereby changing the PTC acquisition
frequency.
FREQ_HOP_SEL_1 setting inserts 1 PTC clock cycle between consecutive measurements.
FREQ_HOP_SEL_15 setting inserts 15 PTC clock cycles.
Higher delay setting will increase the total time taken for capacitance measurement on a given sensor as
compared to a lower delay setting. A desired setting can be used to avoid noise around the same
frequency as the acquisition frequency.
Range:FREQ_HOP_SEL_1 to FREQ_HOP_SEL_16
6.17.
Address 24-25, 84-87: Filter Level
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
24-25
Filter Level for SelfCap
84 – 87
Filter Level for MutualCap
Bit 2
Bit 1
Bit 0
This filter level setting controls the number of samples taken to resolve each acquisition. A higher filter
level setting provides improved signal to noise ratio under noisy conditions, while increasing the total time
for measurement resulting in increased power consumption and response time.
Range: FILTER_LEVEL_1 to FILTER_LEVEL_64
Default: FILTER_LEVEL_8 (For both Self-capacitance and Mutual capacitance)
6.18.
Address 26-27, 88-91: Auto OS
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
26 – 27
Auto OS for SelfCap
88 – 91
Auto OS for MutualCap
Bit 2
Bit 1
Bit 0
Auto oversample controls the automatic oversampling of sensor channels when unstable signals are
detected with the default setting of 'Filter level'.
Enabling Auto oversample results in 'Filter level' x 'Auto Oversample' number of samples taken on the
corresponding sensor channel when an unstable signal is observed. In a case where 'Filter level' is set to
FILTER_LEVEL_4 and 'Auto Oversample' is set to AUTO_OS_4, 4 oversamples are taken with stable
signal values and 16 oversamples are taken when unstable signal is detected.
Range: AUTO_OS_DISABLE to AUTO_OS_128
Default: AUTO_OS_DISABLE (For both Self-capacitance and Mutual capacitance)
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
28
6.19.
Address 28, 92: Auto Tune
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
22
Auto Tune for SelfCap
66
Auto Tune for MutualCap
Bit 2
Bit 1
Bit 0
Auto tune parameter setting is passed to the touch_xx_sensors_calibrate API in order to allow
users to tune the PTC module for power consumption or noise performance.
AUTO_TUNE_PRSC
When Auto tuning of pre-scaler is selected the PTC uses the user defined internal series resistor setting
(DEF_MUTLCAP_SENSE_RESISTOR) and the pre-scaler is adjusted to slow down the PTC operation to
ensure full charge transfer. Auto tuning of pre-scaler with RSEL_VAL_100 as the series resistor results in
best noise performance while resulting in increased power consumption and touch response time.
AUTO_TUNE_RSEL
When Auto tuning of the series resistor is selected the PTC runs at user defined pre-scaler setting speed
(DEF_MUTLCAP_CLK_PRESCALE) and the internal series resistor is tuned automatically to the optimum
value to allow for full charge transfer. Auto tuning of series resistor with PRSC_DIV_SEL_1 as the PTC
pre-scale results in best case power consumption.
AUTO_TUNE_NONE
When manual tuning option is selected, the user defined values of PTC pre-scaler and series resistor is
used for PTC operation as given in DEF_MUTLCAP_CLK_PRESCALE and
DEF_MUTLCAP_SENSE_RESISTOR.
Default: AUTO_TUNE_PRSC (For both Self-capacitance and Mutual capacitance)
6.20.
Address 29-30, 93: AKS
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
29
AKS for SelfCap Button_0
30
AKS for SelfCap Button_1
93
AKS for MutualCap Slider
In designs, where the sensors are close together or configured for high sensitivity, multiple sensors might
report a detect simultaneously. To allow applications to determine the intended single touch, the touch
library provides the user the ability to configure a certain number of sensors in an AKS group.
When a group of sensors are in the same AKS group, only the first strongest sensor will report detection.
The sensor reporting detection will continue to report detection even if another sensor's delta becomes
stronger. The sensor stays in detect until its delta falls below its detection threshold. If any more sensors
in the AKS group are still in detect only the strongest will report detection. At a given time point, only one
sensor from each AKS group is reported to be in detect.
Range: NO_AKS_GROUP to AKS_GROUP_7
Default: NO_AKS_GROUP (For all Self and Mutual capacitance sensors)
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
29
6.21.
Address 31-32, 94: Detect Threshold
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
31
Detect Threshold for SelfCap Button_0
32
Detect Threshold for SelfCap Button_1
94
Detect Threshold for MutualCap Slider
Bit 1
Bit 0
A sensor’s detect threshold define the quantity the signal must increase above its reference level to
qualify as a potential touch detect. However, the final detection confirmation must satisfy the Detect
Integrator (DI) limit. Larger threshold values desensitize sensors since the signal must change more (i.e.
requires larger touch) to exceed the threshold level. Conversely, lower threshold levels make sensors
more sensitive.
Threshold setting depends on the amount of signal swing when a sensor is touched. Usually, thicker front
panels or smaller electrodes have smaller signal swing on touch, thus require lower threshold levels.
Range: 3 to 255
Default: 20 (Self-capacitance), 30 (Mutual capacitance)
6.22.
Address 33-34, 95: Detect Hysteresis
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
33
Detect Hysteresis for SelfCap Button_0
34
Detect Hysteresis for SelfCap Button_1
95
Detect Hysteresis for MutualCap Slider
Bit 1
Bit 0
This setting is sensor detection hysteresis value. It is expressed as a percentage of the sensor detection
threshold setting. When a sensor goes into detect its threshold level is reduced (by the hysteresis value)
in order to avoid the sensor dither in and out of detect if the signal level is close to original threshold level.
•
Setting of 0 = 50% of detect threshold value (HYST_50)
•
Setting of 1 = 25% of detect threshold value (HYST_25)
•
Setting of 2 = 12.5% of detect threshold value (HYST_12_5)
•
Setting of 3 = 6.25% of detect threshold value (HYST_6_25)
Range: HYST_6_25 to HYST_50
Default: HYST_25 (For all Self and Mutual capacitance sensors)
6.23.
Address 35-36, 96: Position Resolution
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
35
Position Resolution for SelfCap Button_0
36
Position Resolution for SelfCap Button_1
96
Position Resolution for MutualCap Slider
Bit 1
Bit 0
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
30
The rotor or slider needs the position resolution (angle resolution in case of rotor and linear resolution in
case of slider) to be set. Resolution is the number of bits needed to report the position of rotor or slider.
Range: 2 bits to 8 bits
Default: 8bits (For all Self and Mutual capacitance sensors)
6.24.
Address 97: Position Hysteresis
Address
Bit 7
Bit 6
97
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Position Hysteresis for MutualCap Slider
In case of Mutual Cap, the rotor or slider needs the position hysteresis (angle hysteresis in case of rotor
and linear hysteresis in case of slider) to be set. It is the number of positions the user has to move back,
before touch position is reported when the direction of scrolling is changed and during the first scrolling
after user press.
Hysteresis can range from 0 (1 position) to 7 (8 positions). The hysteresis is carried out at 8 bits
resolution internally and scaled to desired resolution; therefore at resolutions lower than 8 bits there might
be a difference of 1 reported position from the hysteresis setting, depending on where the touch is
detected.
•
Position hysteresis is not used in case of self-capacitance method sensors.
Range: 0 to 7
Default: 0 (For Mutual capacitance Slider)
6.25.
Address 37, 99: Detect Integration
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
37
Detect Integration for SelfCap
99
Detect Integration for MutualCap
Bit 1
Bit 0
The QTouch Library features a detect integration mechanism, which confirm detection in a robust
environment. The detect integration (DI) acts as a simple signal filter to suppress false detections caused
by spurious events such as electrical noise.
A counter is incremented each time the sensor delta has exceeded its threshold and stayed there for a
specific number of acquisitions, without going below the threshold levels. When this counter reaches a
preset limit (the DI value) the sensor is finally declared to be touched. If on any acquisition the delta
exceeds the threshold level, the counter is cleared and the process has to start from the beginning. The
DI process is applicable to a 'release' (going out of detect) event as well.
For example, if the DI value is 10, the device has to exceed its threshold and stay there for 10 successive
acquisitions without going below the threshold level, before the sensor is declared to be touched.
Range: 0 to 255
Default: 4
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
31
6.26.
Address 38, 100: Away From Touch Drift (Positive Drift)
Address
6.27.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
38
Away From Touch Drift for SelfCap
100
Away From Touch Drift for MutualCap
Bit 1
Bit 0
Bit 1
Bit 0
Address 39, 101: Towards Touch Drift (Negative Drift)
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
39
Towards Touch Drift for SelfCap
101
Towards Touch Drift for MutualCap
Drift in a general sense means adjusting reference level (of a sensor) to allow compensation for
temperature (or other factor) effect on physical sensor characteristics. Decreasing reference level for
such compensation is called Negative drift and increasing reference level is called Positive drift.
Specifically, the drift compensation should be set to compensate faster for increasing signals than for
decreasing signals.
Signals can drift because of changes in physical sensor characteristics over time and temperature. It is
crucial that such drift be compensated for; otherwise false detections and sensitivity shifts can occur. Drift
compensation occurs only while there is no detection in effect. Once a finger is sensed, the drift
compensation mechanism ceases since the signal is legitimately detecting an object. Drift compensation
works only when the signal in question has not crossed the 'Detect threshold' level.
The drift compensation mechanism can be asymmetric; it can be made to occur in one direction faster
than it does in the other simply by changing the appropriate setup parameters. Signal values of a sensor
tend to increase when an object (touch) is approaching it or a characteristic change of sensor over time
and temperature. Increasing signals should not be compensated quickly, as an approaching finger could
be compensated for partially or entirely before even touching the channel (towards touch drift).
However, an object over the channel which does not cause detection, and for which the sensor has
already made full allowance (over some period of time), could suddenly be removed leaving the sensor
with an artificially suppressed reference level and thus become insensitive to touch. In the latter case, the
sensor should compensate for the object's removal by raising the reference level relatively quickly (away
from touch drift).
Away from Touch Drift Range: 0 to 127
Default: 5
Towards Touch Drift Range: 0 to 127
Default: 20
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
32
6.28.
Address 40, 102: Max On Duration
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
40
Max On Duration for SelfCap
102
Max On Duration for MutualCap
Bit 1
Bit 0
The Maximum ON duration timer monitors such detections; if detection exceeds the timer's settings, the
sensor is automatically recalibrated. After a recalibration has taken place, the affected sensor once again
functions normally even if it still in contact with the foreign object.
Max on duration can be disabled by setting it to zero (infinite timeout) in which case the channel never
recalibrates during a continuous detection (but the host could still command it).
Range: 0 to 255
Default: 0
6.29.
Address 41, 103: Drift Hold Time
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
41
Drift Hold Time for SelfCap
103
Drift Hold Time for MutualCap
Bit 1
Bit 0
Drift Hold Time (DHT) is used to restrict drift on all sensors while one or more sensors are activated. It
defines the length of time the drift is halted after a key detection. This feature is useful in cases of high
density keypads where touching a key or floating a finger over the keypad would cause untouched keys
to drift, and therefore create a sensitivity shift, and ultimately inhibit any touch detection.
Range: 1 to 255
Default: 20
6.30.
Address 42, 104: Away from Touch Recalibration Delay
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
36
Away from Touch Recalibration Delay for SelfCap
78
Away from Touch Recalibration Delay for MutualCap
Bit 0
If any key is found to have a significant negative delta, it is deemed to be an error condition. If this
condition persists beyond away from touch recalibration delay period, then an automatic recalibration is
carried out.
A counter is incremented each time the sensor delta is equal to the away from touch recalibration
threshold and stayed there for a specific number of acquisitions. When this counter reaches a preset limit
(the PRD value) the sensor is finally recalibrated. If on any acquisition the delta is seen to be greater than
the away from touch recalibration threshold level, the counter is cleared and the away from touch drifting
is performed.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
33
For example, if the away from touch recalibration delay setting is 10, then the delta has to drop below the
recalibration threshold and stay there for 10 acquisitions in succession without going below the threshold
level, before the sensor is declared to be recalibrated.
Range: 1 to 255
Default: 20
6.31.
Address 43, 105: Calibration Burst Count - Seq1
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
37
Calibration burst count - Seq1 for SelfCap
79
Calibration burst count - Seq1 for MutualCap
Bit 1
Bit 0
This setting represents the total number of measurements carried out during sensor calibration.
Range: 1 to 255
Default: 8
6.32.
Address 44, 106: Calibration Burst Count - Seq2
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
38
Calibration burst count - Seq2 for SelfCap
80
Calibration burst count - Seq2 for MutualCap
Bit 1
Bit 0
This setting represents the total number of measurements that is considered for performing drifting
reference value during sensor calibration. This value should be less than the Seq1 count value set, as
this is subset of calibration operation.
Range: 1 to 255
Default: 4
6.33.
Address 45, 107: Recalibration Threshold
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
39
Recalibration Threshold for SelfCap
81
Recalibration Threshold for MutualCap
Bit 1
Bit 0
Recalibration threshold is the level beyond which automatic recalibration occurs. Recalibration threshold
is expressed as a percentage of the detection threshold setting. This setting is an enumerated value and
its settings are as follows:
•
Setting of 0 = 100% of detect threshold (RECAL_100)
•
Setting of 1 = 50% of detect threshold (RECAL_50)
•
Setting of 2 = 25% of detect threshold (RECAL_25)
•
Setting of 3 = 12.5% of detect threshold (RECAL_12_5)
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
34
•
Setting of 4 = 6.25% of detect threshold (RECAL_6_25)
However, an absolute value of 4 is the hard limit for this setting. For example, if the detection threshold is
40 and the Recalibration threshold value is set to 4. Although this implies an absolute value of 2 (40 *
6.25% = 2.5), it is hard limited to 4.
Range: RECAL_6_25 to RECAL_100
Default: RECAL_50
6.34.
Address 46-47,108-109: Sensor Post-processing Mode
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
40-41
Sensor post-processing mode for SelfCap
82-83
Sensor post-processing mode for MutualCap
Bit 1
Bit 0
This setting controls the touch library post-processing mode options.
•
Setting of 0 = TOUCH_LIBRARY_DRIVEN
•
Setting of 1 = TOUCH_APPLN_DRIVEN
When TOUCH_LIBRARY_DRIVEN mode is selected, the library self-initiates repeated touch
measurements to resolve touch press, release and calibration. This mode is suited for best response
time.
When TOUCH_APPLN_DRIVEN mode is selected, the library does not initiate repeated touch
measurement to resolve touch press, release and calibration. This mode suits deterministic PTC interrupt
execution time for applications requiring stringent CPU time requirements.
Default: 0
6.35.
Address 48-49, 110-111: Auto OS Signal Stability Limit
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
48-49
Auto OS signal stability limit for SelfCap
110-111
Auto OS signal stability limit for MutualCap
Bit 1
Bit 0
Bit 1
Bit 0
This setting defines the stability limit of the signals for performing over-samples.
Range: 1 to 1000
Default: 20
6.36.
Address 50-51,112-113: Frequency Auto Tune Stability Limit
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
42-43
Frequency auto tune stability limit for SelfCap
84-85
Frequency auto tune stability limit for MutualCap
This setting defines the stability limit of signals for Frequency auto tune calculation.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
35
Range: 1 to 1000
Default: 10
Note: This applies only for FREQ_MODE_HOP
6.37.
Address 52,114: Frequency Auto Tune In Counter
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
44
Frequency auto tune in counter for SelfCap
86
Frequency auto tune in counter for MutualCap
Bit 1
Bit 0
The DEF_XXXXCAP_FREQ_AUTO_TUNE_IN_CNT parameter is used to trigger the frequency auto tune. If
sensor signal change at each frequency exceeds the value specified as DEF_XXXXCAP_
FREQ_AUTO_SIGNAL_STABILITY_LIMIT for DEF_XXXXCAP_FREQ_AUTO_TUNE_IN_CNT, then
frequency auto tune will be triggered at this frequency.
Range: 1 to 255
Default: 12
Note: The Frequency Auto Tune feature and related parameters are available only in FREQ_MODE_HOP
mode.
6.38.
Address 54-55,116-117: Noise Measurement Signal Stability Limit
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
46-47
Noise measurement signal stability limit for SelfCap
88-89
Noise measurement signal stability limit for MutualCap
Bit 0
This setting defines the stability limit of signals for noise calculation.
Range: 1 to1000
Default: 10
6.39.
Address 56,118: Noise Measurement Noise Limit
This setting uses to set the noise limit cou
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
48
Noise measurement noise limit for SelfCap
90
Noise measurement noise limit for MutualCap
Bit 1
Bit 0
nter to trigger sensor lockout functionality.
Range: 1 to 255
Default: 12
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
36
6.40.
Address 57,119: Noise Measurement Sensor Lockout Setting
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
49
Noise measurement sensor lockout setting for SelfCap
91
Noise measurement sensor lockout setting for MutualCap
Bit 0
This setting defines noisy senor lockout setting when the measured noise exceeds the noise limit and
does not report a touch.
•
Setting of 0 = SINGLE_SENSOR_LOCKOUT
•
Setting of 1 = GLOBAL_SENSOR_LOCKOUT
•
Setting of 2 = NO_LOCKOUT
Default: 0
6.41.
Address 58,120: Noise Measurement Lockout Count Down
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
50
Noise measurement lockout count down for SelfCap
92
Noise measurement lockout count down for MutualCap
Bit 0
If the sensor signal moves from noisy to a good condition and stays there for a ‘Lockout Countdown’
number of measurements, the sensor is unlocked and sensors are ready for touch detection and drifting
is enabled.
Note: This parameter is valid only for global lockout.
Range: 1 to 255
Default: 10
6.42.
Address 122 – 125: SelfCap Signal
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
122
SelfCap Button_0 – Signal LSB
123
SelfCap Button_0 – Signal MSB
124
SelfCap Button_1 – Signal LSB
125
SelfCap Button_1 – Signal MSB
Bit 1
Bit 0
Addresses 122 – 125 allow signal data to be read for self-capacitance buttons. There are two bytes of
data for each button. The 16-bit signal which is accessed as two 8-bit bytes, stored LSB first.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
37
6.43.
Address 126 – 129: SelfCap Reference
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
126
SelfCap Button_0 – Reference LSB
127
SelfCap Button_0 – Reference MSB
128
SelfCap Button_1 – Reference LSB
129
SelfCap Button_1 – Reference MSB
Bit 1
Bit 0
Addresses 126 – 129 allow reference data to be read for self-capacitance buttons. There are two bytes of
data for each button. The 16-bit reference which is accessed as two 8-bit bytes, stored LSB first.
6.44.
Address 130-137: MutualCap Signal
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
130
MutualCap Slider Channel_0 – Signal LSB
131
MutualCap Slider Channel_0 – Signal MSB
132
MutualCap Slider Channel_1 – Signal LSB
133
MutualCap Slider Channel_1 – Signal MSB
134
MutualCap Slider Channel_2 – Signal LSB
135
MutualCap Slider Channel_2 – Signal MSB
136
MutualCap Slider Channel_3 – Signal LSB
137
MutualCap Slider Channel_3 – Signal MSB
Bit 1
Bit 0
Addresses 130 – 137 allow signal data to be read for each channel of mutual capacitance slider. There
are two bytes of data for each channel. The 16-bit signal which is accessed as two 8-bit bytes, stored
LSB first.
6.45.
Address 138-145: MutualCap Reference
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
138
MutualCap Slider Channel_0 – Reference LSB
139
MutualCap Slider Channel_0 – Reference MSB
140
MutualCap Slider Channel_1 – Reference LSB
141
MutualCap Slider Channel_1 – Reference MSB
142
MutualCap Slider Channel_2 – Reference LSB
143
MutualCap Slider Channel_2 – Reference MSB
144
MutualCap Slider Channel_3 – Reference LSB
145
MutualCap Slider Channel_3 – Reference MSB
Bit 1
Bit 0
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
38
Addresses 138– 145 allow reference data to be read for each channel of mutual capacitance slider. There
are two bytes of data for each channel. The 16-bit reference which is accessed as two 8-bit bytes, stored
LSB first.
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
39
7.
References
•
•
•
•
•
•
SAM D20 PTC User Guide - http://www.atmel.com/Images/Atmel-42195-Qtouch-Library-PeripheralTouch-Controller_User-Guide.pdf
Atmel SAM D20 Xplained Pro User Guide - http://www.atmel.com/images/atmel-42102-samd20xplained-pro_user-guide.pdf
Atmel AVR3009: Driving QTouch Device with IIC Interface - http://www.atmel.com/images/
doc42064.pdf
Atmel QTouch Library User Guide - http://www.atmel.com/Images/doc8207.pdf
ATSAMD20J18 device datasheet - http://www.atmel.com/Images/Atmel-42129-SAMD20_Datasheet.pdf
Atmel AT03665: ASF Manual (SAM D20) - http://www.atmel.com/images/atmel-42139-asf-manualsam-d20_application-note_at03665.pdf
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
40
8.
Revision History
Doc Rev.
Date
Comments
42325C
04/2016
Revised for QTouch Library 5.8
42325B
01/2015
Revised for QTouch Library 5.4
42325A
06/2014
Initial document release
Atmel AT08774: SAM D20 PTC with I2C Slave [APPLICATION NOTE]
Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
41
Atmel Corporation
©
1600 Technology Drive, San Jose, CA 95110 USA
T: (+1)(408) 441.0311
F: (+1)(408) 436.4200
|
www.atmel.com
2016 Atmel Corporation. / Rev.: Atmel-42325C-SAM-D20-PTC-with-I2C-Slave_Application Note-04/2016
®
®
®
Atmel , Atmel logo and combinations thereof, Enabling Unlimited Possibilities , QTouch and others are registered trademarks or trademarks of Atmel Corporation in
®
®
®
U.S. and other countries. ARM , Cortex , ARM Connected logo, and others are the registered trademarks or trademarks of ARM Ltd. Other terms and product
names may be trademarks of others.
DISCLAIMER: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any
intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL TERMS AND
CONDITIONS OF SALES LOCATED ON THE ATMEL WEBSITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED
OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS AND PROFITS, BUSINESS
INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED
OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this
document and reserves the right to make changes to specifications and products descriptions at any time without notice. Atmel does not make any commitment to
update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive
applications. Atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life.
SAFETY-CRITICAL, MILITARY, AND AUTOMOTIVE APPLICATIONS DISCLAIMER: Atmel products are not designed for and will not be used in connection with any
applications where the failure of such products would reasonably be expected to result in significant personal injury or death (“Safety-Critical Applications”) without
an Atmel officer's specific written consent. Safety-Critical Applications include, without limitation, life support devices and systems, equipment or systems for the
operation of nuclear facilities and weapons systems. Atmel products are not designed nor intended for use in military or aerospace applications or environments
unless specifically designated by Atmel as military-grade. Atmel products are not designed nor intended for use in automotive applications unless specifically
designated by Atmel as automotive-grade.