Texas Instruments ADS1230REF User manual

User's GuideSBAU125A – August 2007 – Revised September 2007
ADS1230REF User's Guide
The ADS1230REF is a reference design for the ADS1230 20-bit, delta-sigma analog-to-digital converter(ADC). It contains all the circuitry and user interface elements needed for a weigh-scale digitizer, and ismeant as an example of good design for a basic weigh-scale system. The ADS1230REF is also suitablefor general evaluation of the ADS1230 device.
The ADS1230REF hardware has the following features:•ADS1230 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 InstrumentsPrecision 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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Contents1 Getting Started ............................................................................................................... 32 Weigh Scale Mode........................................................................................................... 73 Analysis Mode .............................................................................................................. 114 Using the PC Software .................................................................................................... 145 Serial Console .............................................................................................................. 186 Hardware .................................................................................................................... 20Appendix A Schematic and Layout ........................................................................................... 24
List of Figures
1 ADS1230REF Controls and Connectors .................................................................................. 32 4-Wire Load Cell to Terminal Block ....................................................................................... 43 6-Wire Load Cell to Terminal Block ....................................................................................... 54 4-Wire Load Cell to Header ................................................................................................ 55 6-Wire Load Cell to Header ................................................................................................ 56 ADS1230REF PC Software Display ..................................................................................... 157 ADS1230REF Average Data ............................................................................................. 168 ADS1230REF Hardware Block Diagram ................................................................................ 20A-1 ADS1230REF PCB—Top Side ........................................................................................... 26A-2 ADS1230REF PCB—Bottom Side ....................................................................................... 26A-3 ADS1230REF Schematic—ADC ......................................................................................... 27A-4 ADS1230REF Schematic—MCU ......................................................................................... 28A-5 ADS1230REF Schematic—USB ......................................................................................... 29
List of Tables
1 Unit Conversion Factors and Display Formats ........................................................................... 82 Parameters in Configuration Mode ........................................................................................ 93 Modes and Example Displays ............................................................................................ 114 Voltage Display Ranges ................................................................................................... 125 Parameters in Analysis Mode............................................................................................. 136 Console Mode Commands ................................................................................................ 197 Load Cell Header Pinout .................................................................................................. 218 Terminal Block Pinout ..................................................................................................... 22A-1 ADS1230REF Bill of Materials ............................................................................................ 24
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1 Getting Started
1.1 Operating Modes
Getting Started
A diagram of the ADS1230REF is shown in Figure 1 .
Figure 1. ADS1230REF Controls and Connectors
The ADS1230REF operates in one of three modes:•Scale mode: When the mode select switch is in Scale position, the ADS1230REF acts as a basicweigh scale. The scale has tare, range, and calibrate functions, and can display metric (SI) units. Otherparameters 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 theADS1230 device and various measurements are made upon them. Several measurements areavailable, including raw display, voltage, RMS noise, and peak-to-peak measurements. The ADS1230can also be configured directly from this mode. Analysis mode is described in detail in Section 3 .•Configuration mode: Parameters governing the operation of the ADS1230REF can be viewed andaltered 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 isdescribed in Section 3.4 .
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1.2 Controls
1.2.1 Auxiliary Controls
1.3 Power
1.4 Connecting a Load Cell
1.4.1 Connecting a 4-Wire Load Cell to the Terminal Block
EXC-
SNS-
SNS+
SIG+
SIG-
EXC+
OUT+
EXC-
OUT-
EXC+
Getting Started
The main controls for the ADS1230REF are the four buttons and the mode selection slide-switch (seeFigure 1 ).
The slide-switch selects between weigh-scale (Scale) and Analysis modes. The ADS1230REF switchesmodes only when it is displaying data. If the switch is changed in a configuration mode, nothing happensuntil the configuration mode is exited. At that time the ADS1230REF reads the switch and enters theselected mode.
The four buttons have different functions, depending on the operating mode. In Scale mode, the switcheshave the functions in the box labeled SCALE. In Analysis mode, the switches have the functions shown inthe box labeled ANALYSIS. In configuration mode, the switches have the functions shown in the boxlabeled CONFIG.
The buttons also have different names in different modes. In this document, they are identifed by therespective names they have in the mode under discussion.
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 maysolve the problem.
The Programming Mode switch is used to update the firmware. For normal operation, it should be set toJTAG.
To apply power to the ADS1230REF, connect a 9V battery or plug in a 6V–9V ac wall adapter.
AC adapters must be tip positive/sleeve negative. When an ac adapter is plugged in, the board alwaystakes power from it, and not from the battery.
The ADS1230REF is protected against polarity reversal. If a power source is connected in reverse bymistake, the display remains blank. To prevent damage to the board, do not leave a reversed powersource connected for longer than a few seconds.
The ADS1230REF is specifically designed for connection to load cells. Two connectors are provided forthis application. The terminal block is used for load cells having stripped wire connections; the load cellheader is for load cells having a header connector. The terminal block provides connections to thereference input (or power supply) and the header has switched excitation.
Figure 2 shows the connection of a 4-wire load cell to the terminal block. In this configuration, the load cellis excited by the +5V power supply, and the ADC reference is taken from the power supply.
For this configuration, the reference select switch must be in the +5VA position.
Figure 2. 4-Wire Load Cell to Terminal Block
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1.4.2 Connecting a 6-Wire Load Cell to the Terminal Block
EXC-
SNS-
SNS+
SIG+
SIG-
EXC+
OUT+
EXC-
SENSE-
OUT-
SENSE+
EXC+
1.4.3 Connecting a 4-Wire Load Cell to the Header
OUT+
EXC-
OUT-
EXC+
1
2
3
4
5
6
1.4.4 Connecting a 6-Wire Load Cell to the Header
OUT-
EXC+
OUT+
EXC-
SENSE+
SENSE-
1
2
3
4
5
6
Getting Started
Figure 3 shows the connection of a 6-wire load cell to the terminal block. In this configuration, the load cellis excited by the +5V power supply, and the ADC’s reference is taken from the sense wire returning fromthe load cell. The sense wire connects to the excitation wire at the bridge sensor.
Figure 3. 6-Wire Load Cell to Terminal Block
Figure 4 shows the connection of a 4-wire load cell to the header. In this configuration, the load cell isexcited by the +5V power supply, and the ADC reference is taken from the power supply.
Figure 4. 4-Wire Load Cell to Header
For this configuration, the reference select switch must be in the +5VA position; the EXT position does notwork.
Figure 5 shows the connection of a 6-wire load cell to the header. In this configuration, the load cell isexcited by the +5V power supply, and the ADC reference is taken from the sense wire returning from theload cell. The sense wire connects to the excitation wire at the bridge sensor.
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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1.5 Connecting Other Signal Sources
1.6 Connecting an External Clock
1.7 Common Tasks
1.7.1 Shorted-Input Noise Test
1.7.2 Measuring Mass
Getting Started
In general, the ADS1230REF can accurately measure any voltage in the input range of the ADS1230ADC, as long as the following rules are observed:•Never apply a negative voltage to the inputs of the ADS1230REF. The ADS1230 cannot acceptnegative voltages at its input. Applying negative voltages may damage both the device and theADS1230REF. (The negative signs used in some signal names indicate inversion, not polarity.)•For single-ended signals, ground the negative input or connect it to 2.5V. 2.5V is available from avoltage divider by shorting J7; see Section 6.4.5 for details.•The input range of the amplifier on the ADS1230 does not extend to the supplies. See the ADS1230data sheet for details.
Note that Scale mode is designed only for use with load cells. Although it can be tested with a voltagesource or resistive divider, Scale mode does not, in general, display meaningful data unless a load cell isconnected and calibration is performed.
To connect an external clock, connect a clock oscillator to the EXTCLK test point. No settings need to bechanged; the ADS1230 will automatically use the attached clock.
The clock source must conform to 3.3V TTL or CMOS logic rules.
The noise measurements given in the product data sheet are taken with the inputs shorted to 2.5V. Thesenoise measurements can be replicated on the ADS1230REF with no external hardware. To set up thesemeasurements on the ADS1230REF, 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 markedInput Shorting Jumpers in Figure 1 .)3. Set up the ADS1230 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 MODE button until the word on the left side is RMS.5. While still holding down DISP, press the UNIT 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. Oncethe appropriate number of points is collected, the calculated noise voltage is displayed. This value isthe shorted-input RMS noise voltage, input-referred.
The first RMS noise measurement may be incorrect as a result of device settling. The secondmeasurement is generally correct.
For a detailed description of Analysis mode, see Section 3 .
The following items are required to measure mass with the ADS1230REF:•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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2 Weigh Scale Mode
Weigh Scale Mode
Obtaining a calibration weight:
Before the ADS1230REF can display the mass of an object, it must measure the output of the load cell fora previously known mass. The known mass can be adjusted.
At power-up, the ADS1230REF expects a 5kg mass. If this mass is not available, or if the load cell rangeis 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 toweigh the calibration object on an accurately calibrated scale. If the weight is precalibrated, its givenmass can be used, although this approach is not generally as accurate. (Note that the accuracy of theADS1230REF as a scale directly depends on the accuracy to which the calibration weight can bemeasured.)
2. Switch the mode switch to SCALE mode.3. Press the ENT and SEL buttons simultaneously. The ADS1230REF enters configuration mode.4. Use the PARM buttons to select the screen which shows UNIT =. This screen allows you to select theunits used for the calibration mass. If the units shown are not correct, adjust them using the VALUEbuttons.
5. Use the PARM buttons to select the screen that shows CW= followed by the calibration mass. On thisscreen, you can adjust each digit of the calibration mass separately. Select the digit using the PARMbuttons. The currently-selected digit flashes, and can be adjusted using the VALUE buttons.6. Adjust the calibration mass to match the mass of the calibration weight.7. Press the VALUE buttons simultaneously 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 asdescribed above.5. Move the mode switch to SCALE position. If calibration has not been performed, the display readsNO 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 ADS1230REF willmeasure the mass of an object placed on the load cell (provided that the mass of the object is within thedevice range).
Weigh scale mode is described in detail in Section 2 .
In weigh scale mode, the ADS1230REF displays mass.
(1)
Mass is displayed in either SI or avoirdupoisunits based on the voltage received from a load cell.
The ADS1230REF operates in Scale mode when the mode switch is set to the Scale position.
To accurately calculate mass, the ADS1230REF must have calibration information for the load cell. Whenscale mode is first entered, the ADS1230REF displays NO CAL, because the ADS1230REF has nocalibration data when it is powered on.
By default, mass is calculated from the average of four successive readings from the ADC. The number ofpoints 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 beaccurately inferred from this voltage as long as a calibration is accurately performed, the downward force of gravity remains constant (asit 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 conditionschange, a new calibration must be performed.
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2.1 Display
2.1.1 Calculation of Mass
m =
wfs
c-cfs zs
(1)
2.2 Button Functions
2.2.1 TARE
Weigh Scale Mode
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, gramsare converted to the desired display unit using the conversion factors given in Table 1 .
xxx(2)
The avoirdupois units used by the ADS1230REF are equal in the imperial and U. S. customary systems.
Table 1. Unit Conversion Factors and Display Formats
Unit Multiplier Format
micrograms ( μg) 10
6
nnn.nnnugmilligrams (mg) 1000 nnn.nnnmggrams (g) 1 nnn.nnngkilograms (kg) 10
–3
nnn.nnnkgounces (oz) 0.035274 nnn.nnnozpounds (lb) 0.0022046 nnn.nnnlbstone (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 fourteenpounds; weight in stone is commonly expressed as a number of stone followed by a number of pounds.On the ADS1230REF, two digits are shown for stone, followed by st, followed by pounds displayed to twodecimal places.
Mass is calculated from ADC code using the formula:w = mc + w
zs
– w
twhere:
•w= mass•c= the ADC code•w
t
= t are weight•m, w
zs
, wt = values determined in the calibration process
mis a calibration constant, and is calculated using Equation 1 :
where w
fs
is the user-specified calibration mass, c
fs
is the ADC code taken with the calibration massapplied, and c
zs
is the ADC measurement taken with no load.
w
zs
, the zero-scale mass, is calculated from m and c
zs
using Equation 2 :w
zs
= –mc
zs
(2)
The tare function allows the mass of a substance to be measured separately from the mass of itscontainer. When the TARE button is pressed, the scale measures the mass and records it. This reading issubtracted 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
2.2.3 CAL
2.3 Calibration
2.4 Configuration
Weigh Scale Mode
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.
Pressing CAL initiates the two-point calibration sequence. See Section 2.3 for details.
Two-point calibration is performed by pressing the CAL button. When this button is pressed, the boardexecutes 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 CALWEIGHT.
5. The user places a weight on the load cell and presses any button. The weight should have the massthat was selected in the configuration mode.6. The board measures the load cell voltage and records it as the calibration weight.
New calibration data is lost when power is removed. To prevent this data loss, calibration data can besaved, with other board settings, to flash memory. See Section 3.4.1 for details.
The parameters for Scale mode can be adjusted in the configuration mode.
To enter configuration mode, press the VALUE buttons simultaneously. The four buttons then assume thefunctions shown in the CONFIG box. To exit Configuration mode, press the VALUE buttonssimultaneously again. This function does not cause parameters to be adjusted, because only buttonreleases are detected in Configuration mode.
Configuration mode contains a number of adjustable parameters. To scroll through the availableparameters, use the PARM buttons. To change the parameter values, use the VALUE buttons.
Some items in configuration mode are not parameters, but commands or gateways to a submenu. Theseitems are labelled as words with a question mark. To enter these or to execute the command, press SELor ENT.
All parameters in the analysis and scale configuration menus are independent, including the parametersfound in both modes.
Table 2 summarizes the available parameters.
Table 2. Parameters in Configuration Mode
Parameter Display Value Range Description
Display units UNIT= μg, mg, g, kg, lb, st, oz Display unitsAverages AVGS= 2–128 Number of points toaverageADC speed SPD= FAST, SLOW Acquisition rateCalibration mass CW= 0–99.9 in various units Calibration mass and unitOffset calibration OCAL? — Offset calibration; see textSave parameters SAVE? — Save parameters; see textVersion number V1.1.0 — Firmware version numberdisplay
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2.4.1 Parameters
Weigh Scale Mode
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 ADS1230, which are calledhigh-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 ADS1230 depends on the frequency of the master clock, f
CLK
. In fast mode, thedata rate is f
CLK
/61440; in slow mode, the data rate is f
CLK
/491520. See the ADS1230 data sheet forfurther information.
The default setting is low-speed mode.
Calibration weight: This parameter gives the expected mass of the calibration weight used in thecalibration procedure (Section 2.3 ). The calibration mass can be given in any of the available units, inthree 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 adjustedwith the VALUE buttons. The PARM buttons are used to select the digit. The unit is adjusted in the samemanner, and flashes when selected.
When the unit is changed, the value changes to the equivalent mass in the new unit.
Offset calibration: This screen has the same function as it does in Analysis mode. See Calibrationsection 2.3 for information.
Save parameters: This screen allows the settings of the ADS1230REF to be stored in flash memory. Itfunctions the same as it does in Analysis mode. When ENT or SEL is pressed on this screen, theADS1230REF saves its settings to flash memory. These settings are loaded from flash memory when theboard 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 ADS1230REF firmware.(1)
The ADS1230REF cannot detect the frequency of the ADS1230 master clock, so it cannot display the actual data rate of the ADS1230device.
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3 Analysis Mode
3.1 Switch Functions
3.2 Measurement Modes
v =
2 1-
24
xvREF
A
·
(3)
Analysis Mode
In Analysis mode, the ADS1230REF analyzes code output from the ADS1230 and displays it in differentways. 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/aRMS n/a +5.789 +17.495N +23.18BITPeak-to-Peak n/a +31.256 +90.293N +21.92BITAveraged n/a +1676001 +499.488M n/a
The ADS1230REF 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 MODE. This function cycles through the fouravailable measurement types. When DISP is released, the newly selected measurement is made. Tochange units, press UNIT. 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 nameon the display. The measurement modes are described in detail in Section 3.2 .
The ADS1230 itself can be configured directly from this mode, as described in Section 3.1 .
NEW BLOCK: Pressing this switch resets the collection process for the RMS, peak-to-peak, andaveraged measurements.
UNIT: 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. WhileDISP is still pressed, pressing NEW BLOCK / MODE cycles through the available measurement modes.
CHIP: Holding this switch down allows the settings of the ADS1230 to be changed, using the PARM(NEW BLOCK) and VAL (UNIT) buttons.
Pressing PARM while DISP 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 64 and 128 are available.
Data rate is shown on the display as SPD=FAST or SPD=SLOW. See ADC speed in the Parameters sectionfor further information.
If any of these parameters are changed during a multisample measurement, the measurement isrestarted.
Raw: In this measurement, codes are read from the ADS1230 and displayed. No processing or analysis isdone on the sample stream. Data can be displayed as hexadecimal codes, decimal codes, or volts.
Voltage is calculated according to Equation 3 :
Where:
•A is the converter gain (64 or 128), determined from the programmed gain setting•v
REF
is the voltage at the converter reference input•x is the ADC decimal code
v
REF
is adjustable from Configuration mode. By default, it is 5V.
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s =
N(x )-
ix2
N
i =1
1
Nå
(4)
E = 24 log s :-2 N 0sN¹
24 : s 0
N=
(5)
3.3 Progress Graph
Analysis Mode
The voltage display is autoranging. All ranges are shown with six significant figures having three decimalplaces. The ranges are given in Table 4 .
Table 4. Voltage Display Ranges
VOLTAGE RANGE DISPLAY SUFFIX
Nanovolts < 1 μV nMicrovolts < 1mV uMillivolts < 1V mVolts ≥1V V
RMS noise: In this mode, a number of codes are read from the ADS1230, and an RMS noise calculationis performed on them using the standard-deviation formula (given in Equation 4 ):
The result can be displayed as decimal codes, volts, or an effective number of bits (ENOB). For decimalcodes, s
N
is displayed directly. (Hexadecimal is not available because s
N
may be fractional.) For volts, s
Nis converted to a voltage as in raw mode.
ENOB: E is calculated using Equation 5 :
The zero case is needed when a string of equal codes is read. This can happen when the converter isclipping.
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. Thisevent happens when the mode is first entered, when the converter configuration changes, or when NEWBLOCK is pressed.
The number of codes used in the calculation is selected in Configuration mode; 50 codes are used inlaboratory 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 thedifference between the minimum and maximum is calculated. The result can be displayed in decimal orhexadecimal codes, volts, or noise-free bits (ENOB). Volts are calculated as in raw mode; ENOB iscalculated 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 canbe displayed in decimal codes or volts. (Hexadecimal is not available because the result may befractional.) Volts are calculated as in raw mode.
The number of codes used in the calculation is selectable in Configuration mode.
The row of apostrophes at the top of the display are used to indicate measurement progress. In Rawmode, the apostrophe moves across the display when data is being received from the converter. Theapostrophe 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, thebar graph increases. When the bar graph reaches all the way to the right, the new result is generated andcollection restarts.
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3.4 Configuration
3.4.1 Parameters
Analysis Mode
To enter Configuration mode, press the VALUE buttons simultaneously. The four buttons then assume thefunctions shown in the CONFIG box. To exit Configuration mode, press the VALUE buttonssimultaneously again. This operation does not cause parameters to be adjusted; only button releases aredetected in Configuration mode.
Configuration mode contains a number of adjustable parameters. To scroll through the availableparameters, use the PARM buttons. To change the parameter values, use the VALUE buttons.
Some items in configuration mode are not parameters, but commands or gateways to a submenu. Theseitems are labelled as words with a question mark. To enter these items or to execute the command, pressSEL or ENT.
Although a few of the parameters in the Analysis and Scale configuration menus are the same, thesettings are kept separate between the modes.
Table 5 summarizes the available parameters.
Table 5. Parameters in Analysis Mode
Parameter Display Value Range Description
Averages AVG= 2–128 Number of points for average,peak-to-peak, and RMS modesVoltage Reference VREF= 0.5–5.0 Voltage used in variouscalculationsPower-down mode PDWN? — Power-down mode; see textOffset calibration OCAL? — Offset calibration; see textSave parameters SAVE? — Save parameters; see textVersion number V1.0.0 — Firmware version number display
Averages: Number of points to use in Averaged, RMS noise, and Peak-Peak calculations. The choicesavailable are 2, 4, 8, 10, 16, 32, 50, 64, and 128. The default setting is 50.
Voltage reference: To convert voltages to codes, the ADS1230REF requires the voltage reference level.Since this level cannot be measured, it must be selected manually. This parameter allows the referencelevel to be set.
Each digit of the voltage reference is selected and adjusted separately. Use the PARM buttons to select adigit, and the VALUE buttons to adjust it. The selected digit flashes.
This parameter does not affect the actual voltage reference used. If it is incorrect, voltage calculations willbe wrong. The voltage reference is typically the +5V rail; the default value for this parameter is 5.0V.
Power-down mode: When ENT or SEL is pressed on this screen, the ADS1230REF causes theADS1230 to enter power-down mode. This action occurs by pulling the PDWN line low. While the PDWNline is low, the display reads POWER DN. When a button is pressed from this display, the ADS1230REFpowers 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 ADS1230 is powered down.
Offset calibration: When ENT or SEL is pressed on this screen, the ADS1230REF initiates a hardwareoffset calibration on the ADS1230 by providing two extra shift clock cycles on the next data read cycle, asdescribed in the ADS1230 data sheet .
When ENT or SEL is pressed, the display briefly shows OK, indicating that calibration was performed.
Offset calibration is performed when the ADS1230REF is powered on, but is not automatically performedat any other time.
Version number: This screen displays the version number of the ADS1230REF firmware.
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4 Using the PC Software
4.1 Installation and Setup
4.1.1 First Time Connection of the ADS123xREF
4.2 The Display
Using the PC Software
The ADS1230REF is supplied with software that performs various analyses on data received from theboard via the USB connection. It also provides a means of recording received data to a file.
The program currently runs only on a Microsoft Windows
®
platform. In Windows, the programcommunicates with the ADS1230REF using a virtual COM port driver that causes the USB connection toappear to Windows as a normal serial port. The necessary driver is installed with the EVM software.
The ADS1230REF software is distributed in an installer program calledADS123x-setup-withLVRT-1.1.1.exe (the version number in the file name may differ), distributed onthe CD-ROM or available from Texas Instruments. To install the software, execute this program. Theprogram guides you through the installation process.
Note the following points:•The installer installs two packages: the ADS123xREF program itself, and the TI Virtual COM Portdriver.
•If any version of the ADS123xREF program is already installed, the installer uninstalls it and quits. Youmust 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.
If the ADS1230REF has never been connected to your computer before, Windows detects the device asunknown hardware and takes you through a series of dialogs to install the correct driver. Accept thedefault settings; the driver is present and only needs to be copied to the correct location. If the driver issuccessfully 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 theboard as new hardware. If this action occurs, proceed through the new hardware dialogs as usual, andallow Windows to reinstall the driver.
The ADS1230REF software has a single display; see Figure 6 for a typical display. The major elements ofthe display 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 pointsused in the analysis is adjustable.
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4.3 Starting the Program
Using the PC Software
DC analysis section: The results of RMS noise analysis, peak-to-peak analysis, and a running voltagenumber are shown in this section. The number of analysis points and the reference voltage used forvoltage 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.
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 availableserial port in turn, testing it to see if there is an ADS1230REF connected. The program uses the firstADS1230REF it finds.
Figure 6. ADS1230REF PC Software Display
Although this procedure is conceptually simple, it may not go as smoothly as expected. The followingprocess ensures that the board is found correctly. Note that Steps 1–3 can be done in any order.Step 1. Apply power to the ADS1230REF.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 beingtested. When the board is found, the display reads Idle. Until a board is found, the displaycycles 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 thesearch process. If the board does not respond, pressing the USB Reset switch (SW1) mayhelp.
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4.4 Analysis or Record Mode
4.5 Adjusting Device Parameters
4.6 Acquiring Data
4.6.1 Averaging
Histogram
Strip Chart
Using the PC Software
The program will operate in analysis mode or record mode. Both modes acquire the data and update thedisplays, but record mode also writes the result to the selected file.
To adjust device parameters, use the controls in the Device control box. Each control corresponds to asetting that can also be made from the board itself.
To start receiving and analyzing data from the board, click the Acquire button, located in the lowerright-hand corner of the display. The program begins to receive data from the board, displaying the resultsin near-real time.
It is not possible for the program to adjust board parameters in Analysis mode. For this reason, the boardcontrols are disabled and dimmed while Analysis occurs.
The PC software can process data collected from the board using a sliding-window averager. The controlsfor 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 Pointscontrol, 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 highnumber of averages, the integer results might include only one code; the histogram for that case will beblank. The strip chart display shows both the full precision result of the averages and the integer version,as illustrated in Figure 7 .
Figure 7. ADS1230REF Average Data
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4.6.2 Block Analysis Length
4.6.3 RMS and Peak-to-Peak Noise Analysis
4.6.4 Displaying Volts
4.6.5 Block Acquisition
4.7 Data Recording
Using the PC Software
The histogram, RMS, and peak-to-peak calculations require a set of samples. These calculations areupdated with every group of samples received, and are performed on a block of the most recentlyacquired (or averaged) samples.
The number of samples used is set using the Analysis points control. By default, this number is 50, butcan 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 Analysispoints 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 clearsthe 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.
The RMS and peak-to-peak noise analysis calculations are performed in exactly the same way as they arein the ADS1230REF firmware, as described in Section 3.2 . Each calculation can be displayed in units ofvolts, 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, thisnumber is 50, but can be changed at any time. This control also controls the histogram length.
When units of volts are displayed, the program must have a value for the reference voltage applied to theADS1230 to properly calculate the voltage. Because this voltage cannot be measured using theADS1230REF, 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 adifferent 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.
To enable the program to run reliably on slower computers, results are not calculated each time a sampleis received. Instead, groups of samples are collected and added to an analysis buffer that is processed asit becomes full. This processing delay is timed so that the display updates at least every 0.75 seconds.
The ADS1230REF software can record incoming samples to a text file. This file can be loaded into otherprograms 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 filecontrol, or click the small open folder icon to the right of the control to open a dialog box fromwhich a file can be selected. If the selected file exists already, the program will display awarning. 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 bothcases, 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, aswell as write it to the selected file. As recording proceeds, the recording time indicators areupdated.Step 4. Click Record again to stop the recording when the desired amount of data has beencollected.
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4.7.1 File Format
5 Serial Console
5.1 Using the Console
Serial Console
The selected file is not opened or created until recording begins. If an error occurs at that time, recordingstops and a message displays in the status box.
Recording time is not measured, but calculated from the number of samples collected. The speed is usedto determine the amount of time for each sample. If the data rate is changed at the board, the recordingtime will be incorrect. This change does not affect the data file, except that samples continue to becollected with the different settings.
In Recording mode, analysis proceeds as in Analysis mode; Recording mode is identical to Analysismode, 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 ofthe file is checked only when a new file is selected.
Data files begin with a header that contains the text collected from ADS1230REF, the time of recording,and the speed and gain. Following this header, values are written in either volts or raw codes, with onevalue per line. Line separators are in DOS format, consisting of a carriage return and a line feed. Thisformat can be examined in a text editor and loaded or imported into most other software, includingspreadsheets.
Voltages are calculated using the reference voltage given in the Vref control; it is therefore important thatthis value be correct.
The ADS1230REF provides a console mode that can be used with any Windows terminal emulationprogram, such as Hyperterm™. In Windows, this configuration is done through the Virtual COM Port driversupplied with the EVM software, causing the ADS1230REF to appear in Windows as an extra serial port.
To use the console, load a terminal emulation program and connect to the EVM serial port using thefollowing 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 programdocumentation for details.
To locate the serial port, try higher port numbers first. When the board first starts, it outputs the followingmessage:
ADS1230REF 1.1.0c(c)2005-2007 Texas Instruments1230>
Pressing Reset causes the board to output this message.
The command prompt is always 1230> . Commands are entered at this prompt. Commands consist ofone 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 alsowork.
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5.2 Command Reference
5.2.1 P—Set PGA
5.2.2 R—Set Data Rate
5.2.3 K—Perform Offset Calibration
5.2.4 V—Show Version
Serial Console
The available commands are listed in Table 6 . In this table, values in brackets indicate a range or list ofpossible characters. A dash ( –) indicates a range, and commas ( ,) indicate a list.
Table 6. Console Mode Commands
COMMAND FORMAT OPERATION
P Set PGAP [0,1]
R Set data rateR [F,S]
Perform offsetK
K
calibration
Show firmwareV
V
version
S Start streamingS
D Read data onceD
Q Query parametersQ
Console mode does not interrupt standalone operation. It is always available, even when the standalonemode is in use. However, if parameters are changed using both the console and standalone modes,parameters may become out of sync.
This command sets the gain of the ADS1230 PGA, according to these parameters:•P0—sets gain to 64•P1—sets gain to 128•P—(with no argument) prints the current gain setting
This command sets the speed of the ADS1230 according to these parameters:•RF—sets rate to fast•RS—sets rate to slow•R—(with no argument) prints the current data rate settingNote that the actual data rate depends on the frequency of the device clock.
Initiates an offset calibration on the ADS1230, using the method described in the datasheet.
Displays a message containing the firmware version and copyright notice.
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5.2.5 S—Start Streaming
5.2.6 D—Collect One Sample
5.2.7 C—Set Channel
5.2.8 Q—Query Parameters
6 Hardware
USB-SERIAL
INTERFACE
POWER
SUPPLY
LOAD CELL
CONNECTORS
INPUT
FILTERING
MSP430F449
USB CONNECTOR
LCD SWITCHES
ADS1230
+5V
+3.3V
CH1
SPI
GPIO
UART
Hardware
When Sis issued, the ADS1230REF begins printing raw output codes from the ADS1230 in hexadecimalformat, separated by new lines. The device iterates continuously until a character is received from theserial port.
Sis used primarily by the EVM software for data collection.
Issuing the Dcommand causes the ADS1230REF to report the latest collected sample from the ADS1230.The sample is displayed in raw hexadecimal.
This command has no effect on the ADS1230 since there is only one channel.•C0—set to channel 0•C—(with no arguments) prints the current channel, always CHAN=0
Qcauses the ADS1230REF to issue a coded string summarizing the current settings. The format of thestring is:P[0,1]R[F,S]OIC0
followed by a carriage-return and linefeed.
A block diagram of the ADS1230REF is shown in Figure 8 . The schematic and layout drawings are givenin Appendix A .
Figure 8. ADS1230REF Hardware Block Diagram
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