TI1 ERJ-3GEYJ152V User guide Datasheet

User's Guide
SBAU120B – November 2005 – Revised July 2011
ADS1232REF User's Guide
The ADS1232REF is a reference design for the ADS1232 24-bit, delta-sigma analog-to-digital converter
(ADC). It contains all the circuitry and user interface elements needed for a weigh-scale digitizer, and is
meant as an example of good design for a basic weigh-scale system. The ADS1232REF is also suitable
for general evaluation of the ADS1232 device. Additionally, performance results obtained with the
ADS1232REF are applicable to the ADS1234, a device with identical performance.
The ADS1232REF hardware has the following features:
• ADS1232 ADC
• Connections for load cells or other voltage sources
• Low-side excitation switch on the load cell header connector
• Ample EMI/RFI suppression between the ADC and rest of design
• Eight-digit starburst LCD readout
• USB connection for firmware updates and remote control
• Designed for very low power consumption
• Battery (9V) or wall power
Version 1.1.0 of the firmware includes the following features:
• Weigh-scale mode with two-point calibration
• Complete configuration of the device
• Real-time peak-to-peak and RMS noise calculation
• Autoranging voltage display
• Noise displayed in volts, codes, and bits
• Voltage displayed in volts or codes
• Adjustable averaging mode
• Raw hexadecimal code display
• Simple and fast configuration
• Parameters saved to internal flash memory
• Computer link
Graphical PC software is also provided for histogram display, datalogging, and device control.
We welcome bug reports and suggestions for additional features; please contact the Texas Instruments
Precision Analog Applications Group.
Hyperterm is a trademark of Microsoft Corporation.
Windows is a registered trademark of Microsoft Corporation.
All other trademarks are the property of their respective owners.
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Contents
1
Getting Started .............................................................................................................. 3
2
Weigh Scale Mode .......................................................................................................... 7
3
Analysis Mode ............................................................................................................. 11
4
Using the PC Software ................................................................................................... 14
5
Serial Console ............................................................................................................. 18
6
Hardware ................................................................................................................... 20
Appendix A
Schematic and Layout ........................................................................................... 23
List of Figures
1
ADS1232REF Controls and Connectors ................................................................................. 3
2
4-Wire Load Cell to Terminal Block
4
3
6-Wire Load Cell to Terminal Block
5
13
......................................................................................
......................................................................................
4-Wire Load Cell to Header................................................................................................
6-Wire Load Cell to Header................................................................................................
ADS1232REF Software Display .........................................................................................
ADS1232REF Average Data .............................................................................................
ADS1232REF Hardware Block Diagram ...............................................................................
ADS1232REF PCB—Top Side ..........................................................................................
ADS1232REF PCB—Bottom Side ......................................................................................
ADS1232REF Schematic—ADC ........................................................................................
ADS1232REF Schematic—MCU ........................................................................................
ADS1232REF Schematic—USB ........................................................................................
1
Unit Conversion Factors and Display Formats .......................................................................... 8
2
Parameters in Configuration Mode ....................................................................................... 9
3
Modes and Example Displays ........................................................................................... 11
4
Voltage Display Ranges .................................................................................................. 12
5
Parameters in Analysis Mode ............................................................................................ 13
6
Console Mode Commands ............................................................................................... 19
7
Load Cell Header Pinout
8
Terminal Block Pinout ..................................................................................................... 22
9
ADS1232REF Bill of Materials
4
5
6
7
8
9
10
11
12
5
5
15
16
20
25
25
26
27
28
List of Tables
2
ADS1232REF User's Guide
.................................................................................................
..........................................................................................
21
23
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Getting Started
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1
Getting Started
Figure 1 shows a diagram of the ADS1232REF.
Figure 1. ADS1232REF Controls and Connectors
1.1
Operating Modes
The ADS1232REF operates in one of three modes:
• Scale mode: When the mode select switch is in Scale position, the ADS1232REF acts as a basic
weigh scale. The scale has tare, range, and calibrate functions, and can display metric (SI) units. Other
parameters can be configured in configuration screens. Scale mode is described in detail in Section 2.
• Analysis mode: When the mode select switch is in Analysis position, codes are taken directly from the
ADS1232 device and various measurements are made upon them. Several measurements are
available, including raw display, voltage, RMS noise, and peak-to-peak measurements. The ADS1232
can also be configured directly from this mode. Analysis mode is described in detail in Section 3.
• Configuration mode: Parameters governing the operation of the ADS1232REF can be viewed and
altered in this mode. Scale and Analysis modes have different options in configuration mode:
configuration for Scale mode is described in Section 2.4, and configuration for Analysis mode is
described in Section 3.4.
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Controls
The main controls for the ADS1232REF are the four buttons and the mode selection slide-switch (see
Figure 1).
The slide-switch selects between weigh-scale (Scale) and Analysis modes. The ADS1232REF switches
modes only when it is displaying data. If the switch is changed in a configuration mode, nothing happens
until the configuration mode is exited. At that time the ADS1232REF reads the switch and enters the
selected mode.
The four buttons have different functions, depending on the operating mode. In Scale mode, the switches
have the functions in the box labeled SCALE. In Analysis mode, the switches have the functions shown in
the box labeled ANALYSIS. In configuration mode, the switches have the functions shown in the box
labeled CONFIG.
The buttons also have different names in different modes. In this document, they are identifed by the
respective names they have in the mode under discussion.
1.2.1
Auxiliary Controls
The Reset switch resets the board, except for the USB interface.
The USB Reset switch resets the USB interface. If USB communication fails, pressing USB Reset may
solve the problem.
The Programming Mode switch is used to update the firmware. For normal operation, it should be set to
JTAG.
1.3
Powering the Board
To apply power to the ADS1232REF, connect a 9V battery or plug in a 6V to 9V ac wall adapter.
AC adapters must be tip positive/sleeve negative. When an ac adapter is plugged in, the board always
takes power from it, and not from the battery.
The ADS1232REF is protected against polarity reversal. If a power source is connected in reverse by
mistake, the display remains blank. To prevent damage to the board, do not leave a reversed power
source connected for longer than a few seconds.
1.4
Connecting a Load Cell
The ADS1232REF is specifically designed for connection to load cells. Two connectors are provided for
this application. The terminal block is used for load cells having stripped wire connections; the load cell
header is for load cells having a header connector. The terminal block provides connections to the
reference input, the power supply, and both input channels. The header has switched excitation.
1.4.1
Connecting a 4-Wire Load Cell to the Terminal Block
Figure 2 shows the connection of a 4-wire load cell to the terminal block. In this configuration, the load cell
is excited by the +5V power supply, and the ADC’s reference is taken from the power supply.
OUTEXC+
OUT+
EXC-
GND
REFIN2+
IN2REF+
IN1+
IN1+5VA
Figure 2. 4-Wire Load Cell to Terminal Block
For this configuration, the reference select switch must be in the +5VA position.
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1.4.2
Connecting a 6-Wire Load Cell to the Terminal Block
Figure 3 shows the connection of a 6-wire load cell to the terminal block. In this configuration, the load cell
is excited by the +5V power supply, and the ADC reference is taken from the sense wire returning from
the load cell. The sense wire connects to the excitation wire at the bridge sensor.
OUTSENSE+
EXC+
GND
REFIN2+
IN2REF+
IN1+
IN1+5VA
OUT+
EXCSENSE-
Figure 3. 6-Wire Load Cell to Terminal Block
For this configuration, the reference select switch should be in the EXT position for best performance. The
+5V position also works, but may not perform as well.
1.4.3
Connecting a 4-Wire Load Cell to the Header
Figure 4 shows the connection of a 4-wire load cell to the header. In this configuration, the load cell is
excited by the +5V power supply, and the ADC reference is taken from the power supply.
EXC+
OUT+
OUTEXC-
6
5
4
3
2
1
Figure 4. 4-Wire Load Cell to Header
For this configuration, the reference select switch must be in the +5VA position; the EXT position will not
work.
1.4.4
Connecting a 6-Wire Load Cell to the Header
Figure 5 shows the connection of a 6-wire load cell to the header. In this configuration, the load cell is
excited by the +5V power supply, and the ADC reference is taken from the sense wire returning from the
load cell. The sense wire connects to the excitation wire at the bridge sensor.
EXC+
SENSE+
OUT+
OUTSENSEEXC-
6
5
4
3
2
1
Figure 5. 6-Wire Load Cell to Header
For this configuration, the reference select switch should be in the EXT position for best performance. The
+5V position also works, but the device may not perform as well.
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Connecting Other Sources
In general, the ADS1232REF can accurately measure any voltage in the input range of the ADS1232
ADC, as long as the following rules are observed:
• Never apply a negative voltage to the inputs of the ADS1232REF. The ADS1232 cannot accept
negative voltages at its input. Applying negative voltages may damage both the device and the
ADS1232REF. (The negative signs used in some signal names indicate inversion, not polarity.)
• Two channels are available. Be sure that the switch is set to the correct channel.
• For single-ended signals, ground the negative input or connect it to 2.5V. 2.5V is available from a
voltage divider by shorting J7; see Section 6.4.5 for details.
• The input range of the amplifier on the ADS1232 does not extend to the supplies. See the ADS1232
data sheet for details.
Note that Scale mode is designed only for use with load cells. Although it can be tested with a voltage
source or resistive divider, Scale mode does not, in general, display meaningful data unless a load cell is
connected and calibration is performed.
1.6
Connecting an External Clock
To connect an external clock, connect a clock oscillator to the EXTCLK test point. No settings need to be
changed; the ADS1232 will automatically use the attached clock.
The clock source must conform to 3.3V TTL or CMOS logic rules.
1.7
1.7.1
Common Tasks
Shorted-Input Noise Test
The noise measurements given in the product data sheet are taken with the inputs shorted to 2.5V. These
noise measurements can be replicated on the ADS1232REF with no external hardware. To set up these
measurements on the ADS1232REF, perform the following steps:
1. Move the mode switch to Analysis mode.
2. Short jumpers J8 and J7. (These jumpers are located very near the terminal block, and are marked
Input Shorting Jumpers in Figure 1.)
3. Set up the ADS1232 as desired, as described in the previous sections.
4. Hold down the DISP button. The display shows the current display mode. While holding down DISP,
press the UNIT button until the word on the left side is RMS.
5. While still holding down DISP, press the MODE button until the word on the right side is VOLT.
6. Release the DISP button. The display shows the word GOT followed by an increasing number. Once
the appropriate number of points is collected, the calculated noise voltage is displayed. This value is
the shorted-input RMS noise voltage, input-referred.
The first RMS noise measurement may be incorrect as a result of device settling. The second
measurement is generally correct.
For a detailed description of Analysis mode, see Section 3.
1.7.2
Measuring Mass
The following items are required to measure mass with the ADS1232REF:
• A load cell, connected as described in Section 1.4
• An object of known mass within the load cell range
To avoid performing calibration on each power-up, you can save the calibration settings to flash memory.
See Section 3.4.1 for details.
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Obtaining a calibration weight:
Before the ADS1232REF can display the mass of an object, it must measure the output of the load cell for
a previously known mass. The known mass can be adjusted.
At power-up, the ADS1232REF expects a 5kg mass. If this mass is not available, or if the load cell range
is not compatible with this mass, the calibration mass can be changed in the following manner:
1. Determine the mass of the calibration weight. The most accurate way to determine the mass is to
weigh the calibration object on an accurately calibrated scale. If the weight is precalibrated, its given
mass can be used, although this approach is not generally as accurate. (Note that the accuracy of the
ADS1232REF as a scale directly depends on the accuracy to which the calibration weight can be
measured.)
2. Switch the mode switch to SCALE mode.
3. Press the PARM buttons simultaneously. The ADS1232REF enters configuration mode.
4. Use the ENT and SEL buttons to select the screen which shows UNIT=. This screen allows you to
select the units used for the calibration mass. If the units shown are not correct, adjust them using the
PARM buttons.
5. Use the VALUE buttons to select the screen that shows CW= followed by the calibration mass. On this
screen, you can adjust each digit of the calibration mass separately. Select the digit using the VALUE
buttons. The currently-selected digit flashes, and can be adjusted using the PARM buttons.
6. Adjust the calibration mass to match the mass of the calibration weight.
7. Press the PARM buttons to exit the configuration mode.
Preparing Scale mode:
Do the following steps to set up the scale mode:
1. Connect the load cell.
2. If the input shorting jumpers J8 and J7 are connected, disconnect them (see Figure 1).
3. Obtain a weight of known mass.
4. If the mass of the weight is not equal to the configured calibration mass, adjust the calibration mass as
described above.
5. Move the mode switch to SCALE position. If calibration has not been performed, the display reads
NO CAL.
6. Press the CAL button, and follow the calibration procedure given in Section 2.3.
If the calibration is performed properly, and the load cell is connected correctly, the ADS1232REF will
measure the mass of an object placed on the load cell (provided that the mass of the object is within the
device range).
Weigh scale mode is described in detail in Section 2.
2
Weigh Scale Mode
In weigh scale mode, the ADS1232REF displays mass. (1) Mass is displayed in either SI or avoirdupois
units based on the voltage received from a load cell.
The ADS1232REF operates in Scale mode when the mode switch is set to the Scale position.
To accurately calculate mass, the ADS1232REF must have calibration information for the load cell. When
scale mode is first entered, the ADS1232REF displays NO CAL, because the ADS1232REF has no
calibration data when it is powered on.
By default, mass is calculated from the average of four successive readings from the ADC. The number of
points for averaging can be adjusted, and averaging can be turned off.
(1)
Load cells do not measure mass directly; they output a voltage proportional to the weight of an object. The mass of an object can be
accurately inferred from this voltage as long as a calibration is accurately performed, the downward force of gravity remains constant (as
it does if the load cell is not moved to a different altitude), and the tilt of the load cell does not change; if either of the latter conditions
change, a new calibration must be performed.
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Display
Weigh scale mode can display mass in these uints: μg (displayed as ug), g, kg, pounds (lb), stone (st),
and ounces (oz). (2)
Internally, mass is measured in grams, and calibration factors are stored in grams. At display time, grams
are converted to the desired display unit using the conversion factors given in Table 1.
blank
(2)
The avoirdupois units used by the ADS1232REF are equal in the imperial and U. S. customary systems.
Table 1. Unit Conversion Factors and Display Formats
UNIT
MULTIPLIER
FORMAT
6
micrograms (μg)
10
nnn.nnnug
milligrams (mg)
1000
nnn.nnnmg
grams (g)
1
nnn.nnng
–3
kilograms (kg)
10
nnn.nnnkg
ounces (oz)
0.035274
nnn.nnnoz
pounds (lb)
0.0022046
nnn.nnnlb
stone (st)
157.473 × 10−6
nnstnn.nn
The display format for stone differs from the format used for the other units. One stone is equal to fourteen
pounds; weight in stone is commonly expressed as a number of stone followed by a number of pounds.
On the ADS1232REF, two digits are shown for stone, followed by st, followed by pounds displayed to two
decimal places.
2.1.1
Calculation of Mass
Mass is calculated from ADC code using the formula:
w = m ● c + wzs – wt
where:
• w = mass
• c = the ADC code
• wt = tare weight
• m, wzs, wt = values determined in the calibration process
m is a calibration constant, and is calculated using Equation 1:
wfs
m=
cfs - czs
(1)
where wfs is the user-specified calibration mass, cfs is the ADC code taken with the calibration mass
applied, and czs is the ADC measurement taken with no load.
wzs , the zero-scale mass, is calculated from m and czs using Equation 2:
wzs = –m ● czs
2.2
2.2.1
(2)
Button Functions
TARE
The tare function allows the mass of a substance to be measured separately from the mass of its
container. When the TARE button is pressed, the scale measures the mass and records it. This reading is
subtracted from each subsequent measurement.
The recorded tare value can be reset to zero by holding the TARE button down for at least one second.
When the tare value is to be reset, the display reads TARE OFF.
Tare is also reset following a calibration.
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2.2.2
RANGE
The RANGE button changes the units or range of the display. RANGE cycles through all available units;
see Section 2.1 for details. When the RANGE button is depressed, it displays the selected unit.
2.2.3
CAL
Pressing CAL initiates the two-point calibration sequence. See Section 2.3 for details.
2.3
Calibration
Two-point calibration is performed by pressing the CAL button. When this button is pressed, the board
executes the following command sequence:
1. The board scrolls the message, REMOVE WEIGHT.
2. The user removes all weight from the load cell and presses any button.
3. The board measures the load cell voltage and records it as the zero point.
4. The board scrolls the message PLACE CAL WEIGHT.
5. The user places a weight on the load cell and presses any button. The weight should have the mass
that was selected in the configuration mode.
6. The board measures the load cell voltage and records it as the calibration weight.
New calibration data are lost when power is removed. To prevent this data loss, calibration data can be
saved, with other board settings, to flash memory. See Section 3.4.1 for details.
2.4
Configuration
The parameters for Scale mode can be adjusted in the configuration mode.
To enter configuration mode, press the PARM buttons simultaneously. The four buttons then assume the
functions shown in the CONFIG box. To exit Configuration mode, press the PARM buttons simultaneously
again. This function does not cause parameters to be adjusted, because only button releases are detected
in Configuration mode.
Configuration mode contains a number of adjustable parameters. To scroll through the available
parameters, use the VALUE buttons. To change the parameter values, use the PARM buttons.
Some items in configuration mode are not parameters, but commands or gateways to a submenu. These
items are labelled as words with a question mark. To enter these or to execute the command, press either
of the PARM buttons.
All parameters in the analysis and scale configuration menus are independent, including the parameters
found in both modes.
Table 2 summarizes the available parameters.
Table 2. Parameters in Configuration Mode
PARAMETER
Display units
DISPLAY
VALUE RANGE
UNIT=
μg, mg, g, kg, lb, st, oz
DESCRIPTION
Display units
Channel
CHANNEL
1, 2
Averages
AVGS=
2–128
ADC speed
SPD=
FAST, SLOW
Calibration mass
CW=
0–99.9 in various units
Calibration mass and unit
Offset calibration
OCAL?
—
Offset calibration; see text
Save parameters
SAVE?
—
Save parameters; see text
Version number
V1.1.0
—
Firmware version number
display
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Analog input channel
Number of points to average
Acquisition rate
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Parameters
Display units: The units to use when displaying mass. Available units are μg (displayed as ug), mg, g, kg,
ounces (oz), pounds, (lb), and stone (st). See Section 2.1 for details.
Averages: Number of points to use when reading weight. The choices available are 2, 4, 8, 10, 16, 32,
50, 64, 100, and 128. The default is 50.
ADC speed: This parameter selects between the two data rates on the ADS1232, which are called
high-speed and low-speed. When high-speed mode is selected, FAST is shown; for low-speed mode, SLOW
is shown. (1)
The actual data rate of the ADS1232 depends on the frequency of the master clock, fCLK. In fast mode, the
data rate is fCLK/61440; in slow mode, the data rate is fCLK/491520. See the ADS1232 data sheet for further
information.
The default setting is low-speed mode.
Calibration weight: This parameter gives the expected mass of the calibration weight used in the
calibration procedure (Section 2.3). The calibration mass can be given in any of the available units, in
three significant figures. The unit is independent of the display unit.
Each digit in the mass is adjusted separately. The currently-selected digit flashes, and can be adjusted
with the PARM buttons. The VALUE buttons are used to select the digit. The unit is adjusted in the same
manner, and flashes when selected.
When the unit is changed, the value changes to the equivalent mass in the new unit.
Channel Selection: This parameter selects between the two analog input channels. Channel 1 uses
either the header or the IN1 connections on the terminal block. Channel 2 uses the IN2 connections on
the terminal block.
Offset calibration: This screen has the same function as it does in Analysis mode. See Calibration for
information.
Save parameters: This screen allows the settings of the ADS1232REF to be stored in flash memory. It
functions the same as it does in Analysis mode. When either PARM button is pressed on this screen, the
ADS1232REF saves its settings to flash memory. These settings are loaded from flash memory when the
board is reset or powered on. All operating parameters are saved, including scale calibration settings,
voltage reference, display mode, and units.
Version number: This screen displays the version number of the ADS1232REF firmware.
(1)
10
The ADS1232REF cannot detect the frequency of the ADS1232 master clock, so it cannot display the actual data rate of the ADS1232
device.
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3
Analysis Mode
In Analysis mode, the ADS1232REF analyzes code output from the ADS1232 and displays it in different
ways. Table 3 summarizes the numerous display modes available, together with example displays.
Table 3. Modes and Example Displays
HEX CODE
DEC CODE
VOLTAGE
ENOB
Raw
1992E9H
+1676001
+499.488M
n/a
RMS
n/a
+5.789
+17.495N
+23.18BIT
Peak-to-Peak
n/a
+31.256
+90.293N
+21.92BIT
Averaged
n/a
+1676001
+499.488M
n/a
The ADS1232REF operates in Analysis mode when the mode switch is set to the ANALYSIS position.
The default Analysis mode is RAW HEX.
To change measurement types, hold down DISP and press UNIT. This function cycles through the four
available measurement types. When DISP is released, the newly selected measurement is made. To
change units, press MODE. This option cycles through the available units for the active measurement
type. This procedure can also be done while DISP is depressed; in that case, the new unit is shown by
name on the display. The measurement modes are described in detail in Section 3.2.
The ADS1232 itself can be configured directly from this mode, as described in Section 3.1.
3.1
Switch Functions
UNIT: Pressing this switch resets the collection process for the RMS, peak-to-peak, and averaged
measurements.
MODE: Cycles between available units. Not all units are available in all modes.
DISP: When this switch is pressed, the display shows the current measurement mode and unit. While
DISP is still pressed, pressing UNIT cycles through the available measurement modes.
CHIP: Holding this switch down allows the settings of the ADS1232 to be changed, using the VALUE,
(ENT) and (SEL) buttons.
Pressing ENT while CHIP is pressed down cycles through the available parameters—gain, data rate, and
active channel.
The gain setting is displayed as GAIN= followed by the gain setting. Gains of 1, 2, 64 and 128 are
available.
Data rate is shown on the display as SPD=FAST or SPD=SLOW. See ADC speed in the Parameters section
for further information.
Channel information is shown as Channel followed by the active channel number (1, 2, or TEMP if
measuring the temperature diode voltage).
If any of these parameters are changed during a multisample measurement, the measurement is
restarted.
3.2
Measurement Modes
Raw: In this measurement, codes are read from the ADS1232 and displayed. No processing or analysis is
done on the sample stream. Data can be displayed as hexadecimal codes, decimal codes, or volts.
Voltage is calculated according to Equation 3:
V
v = 24x · REF
A
2 -1
Where:
•
•
•
A is the converter gain (1, 2, 64, or 128), determined from the programmed gain setting
vREF is the voltage at the converter reference input
x is the ADC decimal code
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VREF is adjustable from Configuration mode. By default, it is 5V.
The voltage display is autoranging. All ranges are shown with six significant figures having three decimal
places. The ranges are given in Table 4.
Table 4. Voltage Display Ranges
VOLTAGE RANGE
DISPLAY SUFFIX
Nanovolts
< 1μV
n
Microvolts
< 1mV
u
Millivolts
< 1V
m
Volts
≥ 1V
V
RMS noise: In this mode, a number of codes are read from the ADS1232, and an RMS noise calculation
is performed on them, using the standard-deviation formula in Equation 4:
Ǹȍ
N
sN +
2
1
(xi*x)
N i +1
(4)
The result can be displayed as decimal codes, volts, or effective bits (ENOB). For decimal codes, sN is
displayed directly. (Hexadecimal is not available since sN is generally fractional.) For volts, sN is converted
to a voltage as in raw mode.
ENOB: E is calculated using Equation 5:
E+
NJ
24* log 2 sN : s N 0 0
24 : s N 0 0
(5)
The zero case is needed when a string of equal codes is read. This event can happen when the converter
is clipping.
This measurement requires a number of codes to be read before a calculation can be made. Therefore,
during the first run, the display shows the word GOT followed by the number of samples collected. This
event happens when the mode is first entered, when the converter configuration changes, or when NEW
BLOCK is pressed.
The number of codes used in the calculation is selected in Configuration mode; 50 codes are used in
laboratory characterization, so this value is the default.
Peak-to-peak noise: In this mode, a number of codes are collected, and the absolute value of the
difference between the minimum and maximum is calculated. The result can be displayed in decimal or
hexadecimal codes, volts, or noise-free bits (ENOB). Volts are calculated as in raw mode; ENOB is
calculated in the same way as in RMS mode.
The number of codes used in the calculation is selectable in Configuration mode.
Averaged: In this mode, a number of codes are collected, and the average is calculated. The result can
be displayed in decimal codes or volts. (Hexadecimal is not available because the result may be
fractional.) Volts are calculated as in raw mode.
The number of codes used in the calculation is selectable in Configuration mode.
3.3
Progress Graph
The row of apostrophes at the top of the display are used to indicate measurement progress. In Raw
mode, the apostrophe moves across the display when data is being received from the converter. The
apostrophe moves once for every eight samples collected from the ADC.
In block collection modes, the apostrophes form a bar graph. As the collection of a block proceeds, the
bar graph increases. When the bar graph reaches all the way to the right, the new result is generated and
collection restarts.
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3.4
Configuration
To enter Configuration mode, press the PARM buttons simultaneously. The four buttons then assume the
functions shown in the CONFIG box. To exit Configuration mode, press the PARM buttons simultaneously
again. This operation does not cause parameters to be adjusted; only button releases are detected in
Configuration mode.
Configuration mode contains a number of adjustable parameters. To scroll through the available
parameters, use the VALUE buttons. To change the parameter values, use the PARM buttons.
Some items in Configuration mode are not parameters, but commands or gateways to a submenu. These
items are labelled as words with a question mark. To enter these items or to execute the command, press
either PARM button.
Although a few of the parameters in the Analysis and Scale configuration menus are the same, the
settings are kept separate between the modes. For example, input channel 1 can be selected in Scale
mode while input channel 2 is selected in Analysis mode. In this setup, when the ADS1232REF switches
from Scale to Analysis mode, the input channel becomes 2.
Table 5 summarizes the available parameters.
Table 5. Parameters in Analysis Mode
PARAMETER
3.4.1
DISPLAY
VALUE RANGE
Averages
AVG=
2–128
Number of points for average,
peak-to-peak, and RMS modes
DESCRIPTION
Voltage Reference
VREF=
0.5–5.0
Voltage used in various
calculations
Power-down mode
PDWN?
—
Power-down mode; see text
Offset calibration
OCAL?
—
Offset calibration; see text
Save parameters
SAVE?
—
Save parameters; see text
Version number
V1.1.0
—
Firmware version number display
Parameters
Averages: Number of points to use in Averaged, RMS noise, and Peak-Peak calculations. The choices
available are 2, 4, 8, 10, 16, 32, 50, 64, 100, and 128. The default setting is 50.
Voltage reference: To convert voltages to codes, the ADS1232REF requires the voltage reference level.
Since this level cannot be measured, it must be selected manually. This parameter allows the reference
level to be set.
Each digit of the voltage reference is selected and adjusted separately. Use the VALUE buttons to select
a digit, and the PARM buttons to adjust it. The selected digit flashes.
This parameter does not affect the actual voltage reference used. If it is incorrect, voltage calculations will
be wrong. The voltage reference is typically the +5V rail; the default value for this parameter is 5.0V.
Power-down mode: When either PARM button is pressed on this screen, the ADS1232REF causes the
ADS1232 to enter power-down mode. This action occurs by pulling the PDWN line low. While the PDWN
line is low, the display reads POWER DN. When a button is pressed from this display, the ADS1232REF
powers the converter on and returns to the analysis display, exiting configuration mode.
This mode can be used to test the current consumption of the board when the ADS1232 is powered down.
Offset calibration: When either PARM button is pressed on this screen, the ADS1232REF initiates a
hardware offset calibration on the ADS1232 by providing two extra shift clock cycles on the next data read
cycle, as described in the ADS1232 data sheet.
When either PARM button is pressed, the display briefly shows OK, indicating that calibration was
performed.
Offset calibration is performed when the ADS1232REF is powered on, but is not automatically performed
at any other time.
Version number: This screen displays the version number of the ADS1232REF firmware.
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Using the PC Software
4
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Using the PC Software
The ADS1232REF is supplied with software that performs various analyses on data received from the
board via the USB connection. It also provides a means of recording received data to a file. The software
is designed to be used with the ADS1232REF operating in Analysis mode. Not all commands will work
with the ADS1232REF operating in Scale mode; the results will be unpredictable.
The program currently runs only on a Microsoft Windows® platform. In Windows, the program
communicates with the ADS1232REF using a virtual COM port driver that causes the USB connection to
appear to Windows as a normal serial port. The necessary driver is installed with the EVM software.
4.1
Installation and Setup
The ADS1232REF software is distributed in an installer program called
ADS123x-setup-withLVRT-1.1.1.exe (the version number in the file name may differ), distributed on the
CD-ROM or available from Texas Instruments. To install the software, execute this program. The program
guides you through the installation process.
Note the following points:
• The installer installs two packages: the ADS123xREF program itself, and the TI Virtual COM Port
driver.
• If any version of the ADS123xREF program is already installed, the installer uninstalls it and quits. You
must run the installer again to complete the installation.
• If the Virtual COM Port driver is already installed, the installer offers to uninstall it. Do not uninstall it;
cancel this part of the installation.
The installer displays messages reminding you of these points.
4.1.1
First Time Connection of the ADS123xREF
If the ADS1232REF has never been connected to your computer before, Windows detects the device as
unknown hardware and takes you through a series of dialogs to install the correct driver. Accept the
default settings; the driver is present and only needs to be copied to the correct location. If the driver is
successfully installed, Windows does not issue this prompt again.
On some computers, if the board is connected to a different USB port, the operating system detects the
board as new hardware. If this action occurs, proceed through the new hardware dialogs as usual, and
allow Windows to reinstall the driver.
4.2
The Display
The ADS1232REF software has a single display; see Figure 6 for a typical display example. The major
elements of the display are discussed next.
Strip chart: This feature displays a scrolling graph of data received from the board.
Histogram: A sliding histogram of data received from the board is also displayed. The number of points
used in the analysis is adjustable.
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DC analysis section: The results of RMS noise analysis, peak-to-peak analysis, and a running voltage
number are shown in this section. The number of analysis points and the reference voltage used for
voltage calculations are also adjustable here.
Recording section: This feature controls recording of data to a file.
Device control section: This section allows device parameters to be adjusted.
Status display: This display shows messages indicating the current state of the program.
Acquire button: This button starts and stops the running acquisition of data.
4.3
Starting the Program
When the program launches, a screen similar to that shown in Figure 6 appears. Immediately after launch,
the program searches all available serial ports for the board. To do this step, it opens every available
serial port in turn, testing it to see if there is an ADS1232REF connected. The program uses the first
ADS1232REF it finds.
Figure 6. ADS1232REF Software Display
Although this procedure is conceptually simple, it may not go as smoothly as expected. The following
process ensures that the board is found correctly. Note that Steps 1–3 can be done in any order.
Step 1. Apply power to the ADS1232REF.
Step 2. Plug in the USB connector.
Step 3. Start the program.
Step 4. Watch the status display. It reads Scanning followed by the name of the serial port being
tested. When the board is found, the display reads Idle. Until a board is found, the display
cycles through every port, spending approximately one second on each port.
Once the board is detected, the program enters Idle mode and is ready for use.
NOTE: If the board is never detected, it is still possible (and safe) to exit the program during the
search process. If the board does not respond, pressing the USB Reset switch (SW1) may
help.
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4.4
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Analysis or Record Mode
The program operates in analysis mode or record mode. Both modes acquire the data and update the
displays, but record mode also writes the result to the selected file.
4.5
Adjusting Device Parameters
To adjust device parameters, use the controls in the Device control box. Each control corresponds to a
setting that can also be made from the board itself.
4.6
Acquiring Data
To start receiving and analyzing data from the board, click the Acquire button, located in the lower
right-hand corner of the display. The program begins to receive data from the board, displaying the results
in near-real time.
It is not possible for the program to adjust board parameters in Analysis mode. For this reason, the board
controls are disabled and dimmed while Analysis occurs.
4.6.1
Averaging
The PC software can process data collected from the board using a sliding-window averager. The controls
for the averager are found in the Averager box.
To turn the averager on, use the Averaging switch. The number of points averaged is set by the Points
control, and the number of points currently collected is shown in the Collected box.
When the averager is turned on, it is cleared. To reset the averager, turn it off and then on again.
The histogram displays an integer representation of the averaged data. Note that when selecting a high
number of averages, the integer results might include only one code; the histogram for that case is blank.
The strip chart display shows both the full precision result of the averages and the integer version, as
illustrated in Figure 7.
Strip Chart
Histogram
Figure 7. ADS1232REF Average Data
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4.6.2
Block Analysis Length
The histogram, RMS, and peak-to-peak calculations require a set of samples. These calculations are
updated with every group of samples received, and are performed on a block of the most recently
acquired (or averaged) samples.
The number of samples used is set using the Analysis points control. By default, this number is 50, but
can be changed at any time. This value also controls the RMS and peak-to-peak noise analysis lengths.
If the number of samples collected is not yet equal to the number of samples specified by the Analysis
points control, 0s are substituted for the samples not yet received.
In Analysis mode, the analysis can be reset using the button marked Reset analysis. This function clears
the internal analysis buffer. This button cannot be used outside of Analysis and Recording modes.
Analysis is automatically reset when Analysis and Recording modes are entered.
4.6.3
RMS and Peak-to-Peak Noise Analysis
The RMS and peak-to-peak noise analysis calculations are performed in exactly the same way as they are
in the ADS1232REF firmware, as described in Section 3.2. Each calculation can be displayed in units of
volts, codes, or bits, as on the board. See Section 3.2 for detailed descriptions of the calculations.
The number of samples used in each calculation is set using the Analysis points control. By default, this
number is 50, but can be changed at any time. This control also controls the histogram length.
4.6.4
Displaying Volts
When units of volts are displayed, the program must have a value for the reference voltage applied to the
ADS1232 to properly calculate the voltage. Because this voltage cannot be measured using the
ADS1232REF, it is set manually using the Vref control.
The value of Vref defaults to 5V, because the reference is normally taken from the 5V power supply. If a
different reference voltage level is used, the value of Vref should be changed to reflect the different level,
so that voltage calculations are performed correctly.
The Vref control also affects voltages recorded in Record mode.
4.6.5
Block Acquisition
To enable the program to run reliably on slower computers, results are not calculated each time a sample
is received. Instead, groups of samples are collected and added to an analysis buffer that is processed as
it becomes full. This processing delay is timed so that the display updates at least every 0.75 seconds.
4.7
Data Recording
The ADS1232REF software can record incoming samples to a text file. This file can be loaded into other
programs for analysis. Data recording is performed using the controls in the Recording box.
Follow these steps to record data to a file:
Step 1. Select or create a destination file. Either type the file path directly into the Destination file
control, or click the small open folder icon to the right of the control to open a dialog box from
which a file can be selected. If the selected file exists already, the program will display a
warning. Otherwise, type the name of the file that you wish to create.
Step 2. Select a data format. Samples can be recorded as raw (decimal) codes or as volts. In both
cases, the data are written to the file as ASCII data, and the file is a text file.
Step 3. Click the Record button. The program begins to collect and analyze data from the board, as
well as write it to the selected file. As recording proceeds, the recording time indicators are
updated.
Step 4. Click Record again to stop the recording when the desired amount of data has been
collected.
The selected file is not opened or created until recording begins. If an error occurs at that time, recording
stops and a message displays in the status box.
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Recording time is not measured, but calculated from the number of samples collected. The speed is used
to determine the amount of time for each sample. If the data rate is changed at the board, the recording
time will be incorrect. This change does not affect the data file, except that samples continue to be
collected with the different settings.
In Recording mode, analysis proceeds as in Analysis mode; Recording mode is identical to Analysis
mode, except that data is written to a file. See the previous section for documentation on Analysis mode.
When Recording mode begins, if the selected file exists, it is erased and overwritten. The pre-existence of
the file is checked only when a new file is selected.
4.7.1
File Format
Data files begin with a header that contains the text collected from ADS1232REF, the time of recording,
and the speed and gain. Following this header, values are written in either volts or raw codes, with one
value per line. Line separators are in DOS format, consisting of a carriage return and a line feed. This
format can be examined in a text editor and loaded or imported into most other software, including
spreadsheets.
Voltages are calculated using the reference voltage given in the Vref control; it is therefore important that
this value be correct.
5
Serial Console
The ADS1232REF provides a console mode that can be used with any Windows terminal emulation
program, such as Hyperterm™. In Windows, this configuration is done through the Virtual COM Port driver
supplied with the EVM software, causing the ADS1232REF to appear in Windows as an extra serial port.
5.1
Using the Console
To use the console, load a terminal emulation program and connect to the EVM serial port using the
following parameters:
• Baud rate: 115200
• Data bits: 8
• Parity: none
• Stop bits: 1
• Flow control: none
• Local echo: off
• Terminal emulation: ANSI or VT100
Setting up the terminal program is beyond the scope of this document; see the specific terminal program
documentation for details.
To locate the serial port, try higher port numbers first. When the board first starts, it outputs the following
message:
ADS1232REF 1.1.0c (c)2005-2007 Texas Instruments 1232>
Pressing Reset causes the board to output this message.
The command prompt is always 1232> . Commands are entered at this prompt. Commands consist of one
letter possibly followed by arguments. The format of the arguments depends on the command.
Commands are case insensitive. Upper-case characters are printed here, but lower-case characters also
work.
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The available commands are listed in Table 6. In this table, values in brackets indicate a range or list of
possible characters. A dash (–) indicates a range, and commas (,) indicate a list.
Table 6. Console Mode Commands
COMMAND
FORMAT
OPERATION
P
P [0-3]
Set PGA
R
R [F,S]
Set data rate
K
K
Perform offset
calibration
V
V
Show firmware version
S
S
Start streaming
D
D
Read data once
C
C
Set input channel
Q
Q
Query parameters
Console mode does not interrupt standalone operation. It is always available, even when the standalone
mode is in use. However, if parameters are changed using both the console and standalone modes,
parameters may become out of sync.
5.2
5.2.1
Command Reference
P—Set PGA
This command sets the gain of the ADS1232 PGA, according to these parameters:
• P0—sets gain to 1
• P1—sets gain to 2
• P2—sets gain to 64
• P3—sets gain to 128
• P—(with no argument) prints the current gain setting
5.2.2
R—Set Data Rate
This command sets the speed of the ADS1232 according to these parameters:
• RF—sets rate to fast
• RS—sets rate to slow
• R—(with no argument) prints the current data rate setting
Note that the actual data rate depends on the frequency of the device clock.
5.2.3
K—Perform Offset Calibration
Initiates an offset calibration on the ADS1232, using the method described in the product data sheet.
5.2.4
V—Show Version
Displays a message containing the firmware version and copyright notice.
5.2.5
S—Start Streaming
When S is issued, the ADS1232REF begins printing raw output codes from the ADS1232 in hexadecimal
format, separated by new lines. The device iterates continuously until a character is received from the
serial port.
S is used primarily by the EVM software for data collection.
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D—Collect One Sample
Issuing the D command causes the ADS1232REF to report the latest collected sample from the ADS1232.
The sample is displayed in raw hexadecimal.
5.2.7
C—Set Channel
This command sets the desired channel of the ADS1232 programmable gain amplifier in the following
manner:
• C0—sets input to channel AIN1
• C1—sets input to channel AIN2
• CT—sets input channel to specified temperature
• C—(with no arguments) provides the current channel setting
5.2.8
Q—Query Parameters
Q causes the ADS1232REF to issue a coded string summarizing the current settings. The format of the
string is:
P[0-3]R[F,S]OIC[0,1,T]
followed by a carriage-return and linefeed.
6
Hardware
A block diagram of the ADS1232REF is shown in Figure 8. The schematic and layout drawings are given
in Section A.2 at the end of this document.
TO TERMINAL
SWITCHES
LCD
BLOCK
CH2
INPUT
GPIO
CH1
MSP430F449
ADS1232
SPI
FILTERING
UART
+5V
LOAD CELL
POWER
USB-SERIAL
CONNECTORS
SUPPLY
INTERFACE
+3.3V
USB CONNECTOR
Figure 8. ADS1232REF Hardware Block Diagram
6.1
Microcontroller
The ADS1232REF uses the MSP430F449 microcontroller. This device provides an LCD controller,
hardware SPI and UART interfaces, and a multiplier. The latter is important because the firmware must
perform many multiplications.
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6.2
Power Supply
The ADS1232REF operates from +5VDC and +3.3VDC. These supplies are generated by linear
regulators U1 and U2. Input power comes from either wall-adapter connector J2, or battery connector
BT1. J2 is switched; when a connector is plugged in, BT1 is disconnected.
Noise is important because the ADS1232 voltage reference is typically taken from the power supply. The
supplies are heavily bypassed to reduce noise.
6.3
User Interface
The ADS1232REF user interface consists of the display and switches SW2–5 and SW8. Switches are
connected to interrupt-capable GPIOs on the microcontroller, allowing them to wake the microcontroller
from sleep mode.
6.4
ADC Section
The ADC section consists of the ADS1232 device itself and ancillary circuitry.
All signals on the ADS1232 (except for the Channel 2 inputs) are filtered by pass-through capacitors that
help to reject electromagnetic interference (EMI), radio frequency interference (RFI), and noise generated
by the digital circuitry.
6.4.1
Input Circuitry
The ADS1232REF is designed to connect to resistive bridge sensors, particularly load cells. The ADS1232
has two channels. Channel 2 is a direct connection, and does not have filtering. Channel 1 is filtered by
pass-through capacitors C46 and C47 and differential capacitor C7. Common-mode capacitors C32 and
C29 provide additional RF rejection.
6.4.2
Load Cell Header
The load cell header, J6, provides a convenient terminal for load cells having a properly fitted header
connector. It provides excitation and sense connections. The negative excitation line is connected to
ground through analog switch U7, which is controlled by the microcontroller. This arrangement allows for
sleep-and-convert control, which can reduce self-heating in the load cell and conserve power.
The load cell connector’s pinout is given in Table 7. For connection examples, see Section 1.4.3 and
Section 1.4.4.
Table 7. Load Cell Header Pinout
6.4.3
PIN NO.
PIN NAME
1
EXC+
FUNCTION
2
EXCSNS+
3
SIG+
Input for positive load cell output
4
SIG–
Input for negative load cell output
5
EXCSNS–
6
EXC–
Positive excitation; connected to +5VA
Positive sense; connected to external positive reference input
Negative sense; connected to external negative reference input
Negative excitation; connected to ground through switch U7
Input Terminal Block
The input terminal block consists of J4 and J5. It provides connections to all of the analog inputs on the
ADS1232, and connections to the ADS1232REF voltage reference network. Unlike the load cell header,
there are no dedicated excitation outputs. Instead, connections to ground and the 5V supply are provided,
and neither are switched. Also, unlike the header, channel 2 inputs are available on the terminal block.
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The terminal block pinout is given in Table 8.
Table 8. Terminal Block Pinout
TERMINAL NAME
6.4.4
FUNCTION
+5VA
5V analog power-supply output
IN1–
Channel 1 negative input
IN1+
Channel 1 positive input
REF+
Positive reference input
IN2–
Channel 2 negative input
IN2+
Channel 2 positive input
REF–
Negative reference input
GND
Board ground
Voltage Reference
The ADS1232REF is designed to operate either ratiometrically or with an external reference. The two
modes are selected using switch SW7.
In the EXT position, the ADS1232 reference inputs are taken from the load cell connectors. In the +5VA
position, the ADS1232 positive reference input comes from the 5V analog supply, and the negative
reference input is connected to ground.
After the switch is placed a filtering network that consists of resistors R14 and R15, bulk capacitor C4,
pass-through capacitors C44 and C45, and filtering capacitors C28, C30, and C31.
6.4.5
Input Shorting Jumpers
The shorted-input noise test for the ADS1232 is best performed with both inputs connected to 2.5V. To
make this test easy to perform, jumpers J7 and J8 are provided.
Jumper J8 shorts the inputs of channel 1 together. Jumper J7 connects the inverting input to a voltage
divider made from R25 and R26, dividing the power supply by 2. This voltage divider electrically
resembles an ideal bridge sensor.
6.5
USB Interface
The USB interface can be used for firmware download or data communications. Its role in firmware
download is discussed in Section 6.6.
The USB interface consists of USB-to-serial converter U4, a Texas Instruments TUSB3410. This device
incorporates a USB interface module, a microcontroller, and a 16550-type UART. Driver software is
available that causes the device to appear as a serial port on the host PC.
The USB interface is powered separately from the rest of the ADS1232REF; it takes power from the USB
line, through linear regulator U3.
The serial port side of U4 is connected to the microcontroller UART signals. To keep the power domains
separate, and to keep the USB and microcontroller sides from inadvertently powering each other, the
UART is connected through isolators U8 and U9.
6.6
Programming Connections
The MSP430 can be programmed via the dedicated JTAG port or the serial bootstrap loader.
The JTAG connector is not factory-installed. The footprint is similar to an edge-card pattern, and accepts a
standard, dual-row 0.100in header mounted on the side of the board. This header is compatible with
MSP430 parallel-port JTAG adaptors.
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To allow firmware to be downloaded through USB, U4 is connected to the microcontroller bootstrap loader
pins. The DTR and RTS pins are connected to the RST and TCK inputs on the microcontroller to allow the
serial bootstrap loader to operate. These lines are not isolated; instead, they are switched through SW9,
which also connects USB ground and power to the microcontroller ground and power. Normally this switch
is open; it is only switched on when firmware is to be downloaded through USB. This feature also protects
the microcontroller from unknown states on these pins at power-up.
Appendix A Schematic and Layout
The printed circuit board (PCB) layouts for the top and bottom sides of the ADS1232REF are shown in
Figure 9 and Figure 10, respectively. The schematic for the ADS1232REF is shown in Section A.3. The
bill of materials is provided in Table 9.
A.1
Bill of Materials
Table 9. ADS1232REF Bill of Materials
REFERENCE DESIGNATOR
DESCRIPTION
MANUFACTURER
MFG. PART NUMBER
R23, R24
0 1/16W 1% Chip Resistor
Panasonic
ERJ-3GEY0R00V
R17
20 1/4W 5% Chip Resistor
Panasonic
ERJ-8GEYJ200V
R2, R3
33 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ330V
R12–R15
100 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ101V
R11
220 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ221V
R1
1.5K 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ152V
R4–R10, R16
10K 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ103V
R25, R26
20K 1/16W 1% Chip Resistor
Panasonic
ERJ-3EKF2002V
R18, R27
47K 1/10W 5% Chip Resistor
Panasonic
ERJ-3GEYJ473V
R22
200k Potentiometer 200kΩ, 1/4in
SQ
Bourns
3362U-1-204LF
R19-R21
221k 1/16W 1% Chip Resistor
Panasonic
ERJ-3EKF2213V
C1, C2, C16, C17
22pF 50V Ceramic Chip
Capacitor, ±0.5pF, NPO
TDK
C1608C0G1H220J
C29, C30, C31, C32
100pF 16V PPS Film Chip
Capacitor, 2%
Panasonic
ECH-U1C101GX5
C38–C43, C48, C49
100pF Filter High Frequency,
100pF
Murata
NFM21CC101U1H3D
C5, C11, C13–C15
0.01μF 50V Ceramic Chip
Capacitor, ±10%, X7R
TDK
C1608X7R1H103K
C12, C21, C33–C36
0.1μF 50V Ceramic Chip
Capacitor, ±10%, X7R
TDK
C1608X7R1H104K
C6, C7
0.1μF 16V PPS Film Chip
Capacitor, 2%
Panasonic
ECH-U1C104GX5
C9, C10, C22
1μF 16V Ceramic Chip
Capacitor, ±10%, X7R
TDK
C1608X7R1C105K
C37, C44–C47
1μF Filter High-Frequency, 1.0μF Murata
NFM21PC105B1C3D
C23–C28
2.2μF 6.3V Ceramic Chip
Capacitor, ±20%, X5R
TDK
C1608X5R0J225M
C3
4.7μF 16V Ceramic Chip
Capacitor, +80/-20%, Y5V
TDK
C2012Y5V1C475Z
C8, C18–C20
10μF 16V Ceramic Chip
Capacitor, ±20%, X7R
TDK
C3216X7R1C106M
C4
100μF 10V Tantalum Chip
Capacitor, ±10%
Kemet
T494D107K010AT
U6
Analog-to-Digital Converter
Texas Instruments
ADS1232IPW
U5
Microcontroller
Texas Instruments
MSP430F449IPZ
U2, U3
Linear Voltage Regulator, +3.3V
Texas Instruments
TPS77133DGKG4
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Schematic and Layout
23
Bill of Materials
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Table 9. ADS1232REF Bill of Materials (continued)
REFERENCE DESIGNATOR
DESCRIPTION
MANUFACTURER
MFG. PART NUMBER
U1
Linear Voltage Regulator, +5V
Texas Instruments
TPS76350DBVG4
U4
USB to Serial Converter
Texas Instruments
TUSB3410VFG4
U7
Analog Switch, SPST
Texas Instruments
TS5A3166DCKR
U8, U9
Digital Isolator
Texas Instruments
ISO721DG4
U10, U11
Inverter, Single Gate
Texas Instruments
SN74LVC1G04DBVRG4
BT1 (+)
9V Battery Clip Female
Keystone Electronics
594
BT1 (–)
9V Battery Clip Male
Keystone Electronics
593
J1
USB Type B Socket
Mill-Max
897-43-004-90- 000000
J2
2.5mm Power Jack
CUI
PJ-102BH
J6
1 X 6 Header
Samtec
TSW-106-07-G-S
J7, J8
1 X 2 Header
Samtec
TSW-102-07-G-S
J4, J5
3.5mm PCB Terminal Block,
4-position
On Shore Technology
ED555/4DS
N/A
ADS1232 REF PCB
Texas Instruments
6474748
D1
30V, 200mA Schottky Diode
Fairchild Semiconductor
BAT54
D2
Green LED, SMD
Lumex
SSL-LX3052GD
L1
Ferrite Bead Core, 4A 100MHz
Panasonic
EXC-ML20A390U
LCD1
8-Character LCD Display, TN
Type
Varitronix
VIM878-DP-RC-S-LV
SW1–SW6
Push-button Switch
ITT
KSAIM211LFT
SW7
DPDT Slide Switch, Top Actuator NKK
SS22SDP2
SW8
SPDT Slide Switch, Top Actuator NKK
SS12SDP2
SW9
4PDT Slide Switch, RA Actuator
E-Switch
EG4208
TP15
Testpoint
Keystone Electronics
5011
X1
12MHz Quartz Crystal
Citizen
CS10-12.000MABJUT
X2
32.678kHz Quartz Crystal
Epson
C-002RX 32.7680KE: PBFREE
24
Schematic and Layout
SBAU120B – November 2005 – Revised July 2011
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PCB Layout
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A.2
PCB Layout
Figure 9. ADS1232REF PCB—Top Side
Figure 10. ADS1232REF PCB—Bottom Side
SBAU120B – November 2005 – Revised July 2011
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Schematic and Layout
25
Schematic and Layout
TEMP
TP5
Copyright © 2005–2011, Texas Instruments Incorporated
CUI-STACK PJ-102BH
J2
C38
9V
D1
BT1
DOUT
TP6
C40
SCLK
C8
10uF
C9
1uF
+5VA
GAIN0
TP19
C39
1
3
2
5
6
3
4
SCLK
TP9
C41
GAIN1
SPEED
TPS77133DGK
IN
OUT
IN
OUT
EN FB/SENSE
GND
RESET
U2
TPS76350DBV
7
8
1
2
C11
RST
TP4
0.01uF
4
5
TP3
+5V
GAIN1
TP21
C48
+3.3VD
VIN
VOUT
ENABLE
GND
NR/ADJUST
U1
SPEED
TP10
C42
C20
10uF
+3.3VD
C19
10uF
+5V
A0
TP22
C49
R27
47K
PWDN/RST
TP12
EXTCLK
C43
TP11
1
20
19
21
23
24
22
7
8
4
3
6
EXC
TP15
GND
ADS1232IPW
DVDD
GAIN1
GAIN0
SPEED
SCLK
DRDY/DOUT
PDWN
TEMP
A0
XTAL2
CLKIN/XTAL1
DGND
U6
2.2uF
4
2
3
J6
V+
NO
TS5A3166DCK
IN
COM
GND
U7
+5VA
C44
+5VA
5
1
R26
20K
J7
100pF
C31
C28
2.2uF
100pF
C6
0.1uF
HEADER-6
1
2
3
4
5
6
20K
R25
18
16
15
11
12
14
13
9
10
17
5
2
+5VA
EXC+
EXCSNS+
SIG+
SIGEXCSNSEXC-
+5VA
AVDD
REFP
REFN
AINP1
AINN1
AINP2
AINN2
CAP
CAP
AGND
DGND
DGND
2.2uF
C27
2
26
1
C45
2
100pF
C29
C7
0.1uF
100pF
C32
TP13
C47
C46
R24
0
SW-DPDT
SW7
VREF+
R23
0
+5VA
J4
J5
OST_ED555/4DS OST_ED555/4DS
+5VA
J8
100
100
TP14
C4
100uF VREFR15
R14
A.3
1
+3.3VD C26
Schematics
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Schematics
Figure 11. ADS1232REF Schematic—ADC
SBAU120B – November 2005 – Revised July 2011
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PDWN/RST
A0
GAIN0
DOUT
TEMP
+3.3VD
2
4
6
8
10
12
14
1
3
5
7
9
11
13
HEADER-7X2
J3
RST
TDO/TDI
TDI/CLK
TM S
TCK
RST
TCK
M CURX
M CUTX
RESET
SW6
TP20
P1.4/SM CLK
R18
47K
C25
2.2uF
+3.3VD
TEM P
BSLRX
BSLTX
DOUT
EXC
+3.3VD
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
R16
10K
+3.3VD
R8
10K
R7
10K
SW8
NKK_SS12SDP2
SW3
TARE
SW2
SW4
R9
10K
SW5
CONFIG
R10
10K
CAL
SIM O0
TP7
DNP
DOUT
SCLK
SPEED
RANGE
C23
2.2uF
+3.3VD
P2.3/TB2
P2.2/TB1
P2.1/TB0
P2.0/TA2
P1.7/CA1
P1.6/CA0
P1.5/TACLK/ACLK
P1.4/TBCLK/SM CLK
P1.3/TBOUTH/SVSOUT
P1.2/TA1
P1.1/TA0/M CLK
P1.0/TA0
XT2OUT
XT2IN
TDO/TDI
TDI/TCLK
TM S
TCK
RST/NM I
P6.0/A0
P6.1/A1
P6.2/A2
AVSS
DVSS1
AVCC
C24
2.2uF
PDW N/RST
X2
EPS_C-002RX 32.7680K-A:PBFREE
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
221K
221K
S(38)
S(37)
S(36)
S(35)
S(34)
S(33)
S(32)
S(31)
S(30)
S(29)
S(28)
S(27)
S(26)
S(25)
S(24)
S(23)
S(22)
S(21)
S(20)
S(19)
S(18)
S(17)
S(16)
S(15)
S(14)
U5
M SP430F449IPZ
P4.3/SIM O1/S38
P4.4/SOM I1/S37
P4.5/UCLK1/S36
P4.6/S35
P4.7/S34
S33
S32
S31
S30
S29
S28
S27
S26
S25
S24
S23
S22
S21
S20
S19
S18
S17
S16
S15
S14
221K
C15
0.01uF
R21
C14
0.01uF
R20
C13
0.01uF
R19
COM (3)
COM (2)
COM (1)
COM (0)
S(39)
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
P2.4/UTXD0
P2.5/URXD0
P2.6/CAOUT
P2.7/ADC12CLK
P3.0/STE0
P3.1/SIM O0
P3.2/SOM I0
P3.3/UCLK0
P3.4/TB3
P3.5/TB4
P3.6/TB5
P3.7/TB6
P4.0/UTXD1
P4.1/URXD1
DVSS2
DVCC2
P5.7/R33
P5.6/R23
P5.5/R13
R03
P5.4/COM 3
P5.3/COM 2
P5.2/COM 1
COM 0
P4.2/STE1/S39
DVCC1
P6.3/A3
P6.4/A4
P6.5/A5
P6.6/A6
P6.7/A7/SVSIN
VREF+
XIN
XOUT
VeREF+
VREF-/VeREFP5.1/S0
P5.0/S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
Copyright © 2005–2011, Texas Instruments Incorporated
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
C5
LCD1
200K
0.01uF
R22
S(7)
S(8)
S(11)
S(12)
S(15)
S(16)
S(19)
S(20)
S(23)
S(24)
S(27)
S(28)
S(31)
S(32)
S(35)
S(36)
COM (0)
COM (1)
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
SBAU120B – November 2005 – Revised July 2011
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TP8
TP18
M CURX M CUTX
R13 100
S(5)
S(6)
S(7)
S(8)
S(9)
S(10)
S(11)
S(12)
S(13)
R12 100
S(5)
S(6)
S(9)
S(10)
S(13)
S(14)
S(17)
S(18)
S(21)
S(22)
S(25)
S(26)
S(29)
S(30)
S(33)
S(34)
COM (3)
COM (2)
+3.3VD
LCD_DISPLAY
www.ti.com
Schematics
Figure 12. ADS1232REF Schematic—MCU
Schematic and Layout
27
Copyright © 2005–2011, Texas Instruments Incorporated
GND
D+
DVCC
4
3
2
1
C37
R17
20
M UR_NFM 21PC105F1C3D
USB SLAVE CONN
J1
L1
FERRITE BEAD
R1
1.5K
R3
33
C3
4.7uF
USB5V
R2
33
5
6
3
4
C1
22pF
C2
22pF
C17
22pF
OUT
OUT
FB/SENSE
RESET
TPS77133DGK
IN
IN
EN
GND
U3
C16
22pF
12M Hz
X1
TP1
USB_CLK
7
8
1
2
8
18
28
5
6
7
22
26
27
GND
GND
GND
PUR
DP
DM
C18
10uF
CLKOUT
X2
X1/CLKI
U4
10
SDA
10K
11
10K
R5
SCL
R4
TP2
4
USB3.3V
R6
10K
D2
GREEN
R11
220
USB3.3V
1uF
C22
23
24
13
20
16
21
14
15
19
17
SW1
DTR
RTS
RX
TX
USB3.3V
C10
1uF
USB RESET
TUSB3410VF
TEST0
TEST1
CTS
RTS
RI/CP
DTR
DSR
DCD
SOUT/IR_SOUT
SIN/IR_SIN
VDD
3.3V_USB
VREGEN
RESET
SUSPEND
W AKEUP
1
9
2
12
3
25
VCC
VCC
P3.0
P3.1
P3.3
P3.4
2
2
USB3.3V
C12
4
0.1uF
C33
0.1uF
C34
0.1uF
C21
0.1uF
+5VA
4
SN74LVC1G04DBV
U11
SN74LVC1G04DBV
U10
TP17
TX
USB3.3V
5
3
5
Schematic and Layout
3
28
32
31
30
29
TP16
RX
8
6
7
5
1
3
2
4
ISO721D
VCC2
OUT
GND2
GND2
U9
ISO721D
VCC1
VCC1
IN
GND1
U8
ESW_EG4208
SW9
VCC1
VCC1
IN
GND1
VCC2
OUT
GND2
GND2
USB5V
RST
TCK
PROGRAMM ING M ODE
USB3.3V
USB3.3V
+5V
1
3
2
4
+3.3VD
8
6
7
5
+3.3VD
C35
M CUTX
0.1uF
C36
M CURX
0.1uF
Schematics
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Figure 13. ADS1232REF Schematic—USB
SBAU120B – November 2005 – Revised July 2011
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Revision History
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Revision History
Changes from A Revision (September, 2007) to B Revision ......................................................................................... Page
•
•
•
•
•
•
•
•
•
•
Corrected nomenclature errors in Section 1.7.1 ...................................................................................... 6
Revised button descriptions in procedure to obtain a calibration weight .......................................................... 7
Updated Section 2.1.1 ................................................................................................................... 8
Changed button descriptions in Configuration section .............................................................................. 9
Updated Table 2 .......................................................................................................................... 9
Revised Section 2.4.1 .................................................................................................................. 10
Corrected button nomenclature in Section 3 ........................................................................................ 11
Revised button nomenclature in Section 3.4 ........................................................................................ 13
Corrected button nomenclature errors in Section 3.4.1 ............................................................................ 13
Changed first paragraph of Section 4 ................................................................................................ 14
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
SBAU120B – November 2005 – Revised July 2011
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Copyright © 2005–2011, Texas Instruments Incorporated
Revision History
29
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