User's Guide SBAU175A – July 2010 – Revised August 2011 ADS1131REF and ADS1231REF The ADS1131REF and the ADS1231REF are reference designs for delta-sigma analog-to-digital converters (ADCs). The ADS1131REF contains the ADS1131 18-bit device, while the ADS1231REF contains the ADS1231 24-bit device. Both systems contain all the circuitry and user interface elements needed for a weigh-scale digitizer, and are meant as examples of a good design for a basic weigh-scale system. Each system is also suitable for general evaluation of the respectively installed ADC. Throughout this document, the term ADS1x31REF is used to refer to the common features and functions for both systems. The ADS1x31REF hardware has the following features: • ADS1131 ADC for the ADS1131REF and ADS1231 ADC for the ADS1231REF • 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 1.0.0 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. 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SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 1 www.ti.com 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 ADS1x31REF Controls and Connectors ................................................................................. 3 2 4-Wire Load Cell to Terminal Block 3 6-Wire Load Cell to Terminal Block 15 ...................................................................................... 4 ...................................................................................... 5 4-Wire Load Cell to Header................................................................................................ 5 6-Wire Load Cell to Header................................................................................................ 5 ADS1231REF PC Software Display .................................................................................... 15 ADS1x31REF Average Data ............................................................................................. 16 ADS1x31REF Hardware Block Diagram ............................................................................... 20 ADS1x31REF PCB—Top Side .......................................................................................... 25 ADS1x31REF PCB—Layer 1 ............................................................................................ 25 ADS1x31REF PCB—Layer 2 ............................................................................................ 26 ADS1x31REF PCB—Bottom Side ...................................................................................... 26 ADS1x31REF Schematic—ADC ........................................................................................ 27 ADS1x31REF Schematic—MCU ........................................................................................ 27 ADS1x31REF Schematic—USB......................................................................................... 28 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 ADS1x31REF Bill of Materials 4 5 6 7 8 9 10 11 12 13 14 List of Tables 2 ADS1131REF and ADS1231REF ................................................................................................. .......................................................................................... 21 23 SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Getting Started www.ti.com 1 Getting Started A diagram of the ADS1x31REF is shown in Figure 1. Figure 1. ADS1x31REF Controls and Connectors 1.1 Operating Modes The ADS1x31REF operates in one of three modes: • Scale mode: When the mode select switch is in Scale position, the ADS1x31REF 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 installed ADS device and various measurements are made upon them. Several measurements are available, including raw display, voltage, RMS noise, and peak-to-peak measurements. The ADS1131 or ADS1231 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 ADS1x31REF 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. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 3 Getting Started 1.2 www.ti.com Controls The main controls for the ADS1x31REF 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 ADS1x31REF 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 ADS1x31REF 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 Power To apply power to the ADS1x31REF, 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 always takes power from it, and not from the battery. The ADS1x31REF 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 ADS1x31REF 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 (or power supply) and 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 reference is taken from the power supply. For this configuration, the reference select switch must be in the +5VA position. OUTEXC+ OUT+ EXCSNSSNS+ SIG+ SIGEXC+ EXC- Figure 2. 4-Wire Load Cell to Terminal Block 4 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Getting Started www.ti.com 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’s 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+ EXCSNSSNS+ SIG+ SIGEXC+ OUT+ EXCSENSE- Figure 3. 6-Wire Load Cell to Terminal Block 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+ OUTOUT+ EXC- 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 does 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. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 5 Getting Started 1.5 www.ti.com Connecting Other Signal Sources In general, the ADS1x31REF can accurately measure any voltage in the input range of the installed ADS device, as long as the following rules are observed: • Never apply a negative voltage to the inputs of the ADS1x31REF. The installed ADS device cannot accept negative voltages at its input. Applying negative voltages may damage both the device and the ADS1x31REF. (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 a voltage divider by shorting J7; see Section 6.4.5 for details. • The input range of the amplifier on the ADS1131 or ADS1231 does not extend to the supplies. See the ADS1131 data sheet or the ADS1231 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 Note that only the ADS1231 can receive an external clock. To connect an external clock, connect a clock oscillator to the EXTCLK test point. No settings need to be changed; the ADS1231 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 ADS1x31REF with no external hardware. To set up these measurements on the ADS1x31REF, 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 installed ADS device 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. 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 ADS1x31REF: • 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. 6 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Weigh Scale Mode www.ti.com Obtaining a calibration weight: Before the ADS1x31REF 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 ADS1x31REF 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 ADS1x31REF 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 ADS1x31REF enters configuration mode. 4. Use the PARM 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 VALUE buttons. 5. Use the PARM 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 PARM buttons. 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 PARM 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 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 ADS1x31REF 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 ADS1x31REF displays mass. (1) Mass is displayed in either SI or avoirdupois units based on the voltage received from a load cell. The ADS1x31REF operates in Scale mode when the mode switch is set to the Scale position. To accurately calculate mass, the ADS1x31REF must have calibration information for the load cell. When scale mode is first entered, the ADS1x31REF displays NO CAL, because the ADS1x31REF 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. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 7 Weigh Scale Mode 2.1 www.ti.com Display Weigh scale mode can display mass in these units: 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. xxx (2) The avoirdupois units used by the ADS1x31REF 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 ADS1x31REF, 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. 8 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Weigh Scale Mode www.ti.com 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 is 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 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. These items are labelled as words with a question mark. To enter these or to execute the command, press SEL or ENT. 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 Display Value Range Display units Parameter UNIT= μg, mg, g, kg, lb, st, oz Averages AVGS= 2–128 Description Display units Number of points to average ADC speed SPD= FAST, SLOW Calibration mass CW= 0–99.9 in various units Calibration mass and unit Save parameters SAVE? — Save parameters; see text Version number V1.0.0 — Firmware version number display SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Acquisition rate ADS1131REF and ADS1231REF 9 Weigh Scale Mode 2.4.1 www.ti.com 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 installed ADS device, 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 ADS1131 or ADS1231 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 ADS1131 data sheet or the ADS1231 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 VALUE buttons. The PARM 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. Save parameters: This screen allows the settings of the ADS1x31REF to be stored in flash memory. It functions the same as it does in Analysis mode. When ENT or SEL is pressed on this screen, the ADS1x31REF 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 ADS1x31REF firmware. (1) 10 The ADS1x31REF cannot detect the frequency of the ADS1231 master clock, so it cannot display the actual data rate of the ADS1231 device. ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Analysis Mode www.ti.com 3 Analysis Mode In Analysis mode, the ADS1x31REF analyzes code output from the installed ADS device and displays it in different ways. Table 3 summarizes the numerous display modes available, together with example displays. NOTE: The values shown in Table 3 are consistent for a 24-bit device, such as the ADS1231. However, the ADS1131 is an 18-bit device, so the actual number of codes will be fewer than the examples shown here. 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 ADS1x31REF 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 four available measurement types. When DISP is released, the newly selected measurement is made. To change 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 name on the display. The measurement modes are described in detail in Section 3.2. The ADS1131 or ADS1231 itself can be configured directly from this mode, as described in Section 3.1. 3.1 Switch Functions NEW BLOCK: Pressing this switch resets the collection process for the RMS, peak-to-peak, and averaged 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. While DISP is still pressed, pressing NEW BLOCK / MODE cycles through the available measurement modes. CHIP: Holding this switch down allows the settings of the installed ADS device to be changed, using the PARM (NEW BLOCK) and VAL (UNIT) buttons. Pressing PARM while CHIP is pressed down cycles through the available parameters of gain and data rate. The gain setting is displayed as GAIN= followed by the gain setting. The gain setting is for display only, because the gain is fixed at 64 for the ADS1131 and 128 for the ADS1231. Data rate is shown on the display as SPD=FAST or SPD=SLOW. See ADC speed in the Parameters section for further information. If any of these parameters are changed during a multisample measurement, the measurement is restarted. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 11 Analysis Mode 3.2 www.ti.com Measurement Modes Raw: In this measurement, codes are read from the installed ADS device 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: vREF x v= · B-1 A Where: • • • • A is the converter gain (64 for the ADS1131 and 128 for the ADS1231) vREF is the voltage at the converter reference input x is the ADC decimal code B is the number of converter bits, 218 for the ADS1131 and 224 for the ADS1231 (3) 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 installed ADS device, and an RMS noise calculation is performed on them using the standard-deviation formula (given in Equation 4): sN = N 2 1å N i =1(xi - x) (4) The result can be displayed as decimal codes, volts, or an effective number of bits (ENOB). For decimal codes, sN is displayed directly. (Hexadecimal is not available because sN may be fractional.) For volts, sN is converted to a voltage as in raw mode. ENOB: E is calculated using Equation 5: E= N - log2sN : sN ¹ 0 24 : sN = 0 (5) Where N is the maximum number of available bits (18 for the ADS1131 and 24 for the ADS1231). The zero case is needed when a string of equal codes is read. This 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. 12 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Analysis Mode www.ti.com 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. 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. 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 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. These items are labelled as words with a question mark. To enter these items or to execute the command, press SEL or ENT. Although a few of the parameters in the Analysis and Scale configuration menus are the same, the settings are kept separate between the modes. Table 5 summarizes the available parameters. Table 5. Parameters in Analysis Mode Parameter 3.4.1 Display Value Range Description Averages AVG= 2–128 Number of points for average, peak-to-peak, and RMS modes Voltage Reference VREF= 0.5–5.0 Voltage used in various calculations Power-down mode PDWN? — Power-down mode; see text Save parameters SAVE? — Save parameters; see text Version number V1.0.0 — 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, and 128. The default setting is 50. Voltage reference: To convert voltages to codes, the ADS1x31REF 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 PARM buttons to select a digit, 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 will be wrong. The voltage reference is typically the +5V rail; the default value for this parameter is 5.0V. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 13 Using the PC Software www.ti.com Power-down mode: When ENT or SEL is pressed on this screen, the ADS1x31REF causes the installed ADS device 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 ADS1x31REF 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 installed ADS device is powered down. Version number: This screen displays the version number of the ADS1x31REF firmware. 4 Using the PC Software The ADS1x31REF 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 program currently runs only on a Microsoft Windows® platform. In Windows, the program communicates with the ADS1x31REF 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 ADS1x31REF software is distributed in an installer program called ADS1x3x-setup-withLVRT-1.3.0.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 ADS1x3xREF program itself, and the TI Virtual COM Port driver. • If any version of the ADS1x3xREF 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 ADS1x3xREF If the ADS1x31REF 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 ADS1x31REF software has a single display; see Figure 6 for a typical display. The major elements of the 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 points used in the analysis is adjustable. 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. 14 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Using the PC Software www.ti.com 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 ADS1x31REF connected. The program uses the first ADS1x31REF it finds. Note that the title block displays the name of the board found. Figure 6 shows the board found as the ADS1231REF. If the ADS1131REF is connected, the title shows ADS1131REF. Figure 6. ADS1231REF PC 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 ADS1x31REF. 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. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 15 Using the PC Software 4.4 www.ti.com Analysis or Record Mode The program will operate 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 will be 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. ADS1x31REF Average Data 16 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Using the PC Software www.ti.com 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 100, 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 ADS1x31REF 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 100, 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 installed ADS device to properly calculate the voltage. Because this voltage cannot be measured using the ADS1x31REF, 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 ADS1x31REF 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. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 17 Serial Console www.ti.com 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 ADS1x31REF, 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 ADS1x31REF 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 ADS1x31REF 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: ADS1131REF 1.0.0 (c)2010 Texas Instruments 1131> for the ADS1131, or : ADS1231REF 1.0.0 (c)2010 Texas Instruments 1231> for the ADS1231. Pressing Reset causes the board to output this message. The command prompt is always 1131> for the ADS1131 and 1231> for the ADS1231. 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. 18 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Serial Console www.ti.com 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 — Prints the current gain setting R R [F,S] Set data rate V V Show firmware version S S Start streaming D D Read data once 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 has no effect on the ADS1131 or ADS1231 because the device gain is fixed. • P—(with no argument) prints the current gain setting 5.2.2 R—Set Data Rate This command sets the speed of the installed ADS device 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 V—Show Version Displays a message containing the firmware version and copyright notice. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 19 Hardware 5.2.4 www.ti.com S—Start Streaming When S is issued, the ADS1x31REF begins printing raw output codes from the installed ADS device 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. 5.2.5 D—Collect One Sample Issuing the D command causes the ADS1x31REF to report the latest collected sample from the installed ADS device. The sample is displayed in raw hexadecimal. 5.2.6 C—Set Channel This command has no effect on the installed ADS device because there is only one channel. • C0—set to channel 0 • C—(with no arguments) prints the current channel, always CHAN=0 5.2.7 Q—Query Parameters Q causes the ADS1x31REF to issue a coded string summarizing the current settings. The format of the string is: P0R[F,S]OIC0 followed by a carriage-return and linefeed. 6 Hardware A block diagram of the ADS1x31REF is shown in Figure 8. The schematic and layout drawings are given in Appendix A. SWITCHES LCD INPUT GPIO CH1 MSP430F449 ADS1x31 SPI FILTERING UART +5V LOAD CELL POWER USB-SERIAL CONNECTORS SUPPLY INTERFACE +3.3V USB CONNECTOR Figure 8. ADS1x31REF Hardware Block Diagram 20 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Hardware www.ti.com 6.1 Microcontroller The ADS1x31REF 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. 6.2 Power Supply The ADS1x31REF 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 ADC voltage reference is typically taken from the power supply. The supplies are heavily bypassed to reduce noise. 6.3 User Interface The ADS1x31REF 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 installed ADS device itself and ancillary circuitry. All signals on the installed ADS device 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 ADS1x31REF is designed to connect to resistive bridge sensors, particularly load cells. The input channel is filtered by pass-through capacitors C38 and C39 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 the installed ADS device. The ADS device conserves power by allowing excitation current to flow only during conversion. See the ADS1131 data sheet or the ADS1231 data sheet for more information. 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 PIN NO. PIN NAME 1 EXC+ 2 EXCSNS+ 3 SIG+ Input for positive load cell output 4 SIG– Input for negative load cell output 5 EXCSNS– Negative sense; connected to external negative reference input 6 EXC– Negative excitation; connected to ground through installed ADS device SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback FUNCTION Positive excitation; connected to +5VA Positive sense; connected to external positive reference input Copyright © 2010–2011, Texas Instruments Incorporated ADS1131REF and ADS1231REF 21 Hardware 6.4.3 www.ti.com Input Terminal Block The input terminal block consists of J4 and J5. It provides connections to all of the analog inputs on the installed ADS device, and connections to the ADS1x31REF voltage reference network. The terminal block pinout is given in Table 8. Table 8. Terminal Block Pinout TERMINAL NAME 6.4.4 FUNCTION EXC– Negative excitation connected to ground through installed ADS device SNS– Inverting excitation sense input SNS+ Noninverting excitation sense input SIG+ Noninverting input SIG– Inverting input EXC+ Positive excitation output (+5V) or positive reference input Voltage Reference The ADS1x31REF is designed to operate either ratiometrically or with an external reference. The two modes are selected using switch SW7. In the EXT position, the installed ADS reference inputs are taken from the load cell connectors. In the +5VA position, the installed ADS 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 ADS1x31 devices 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 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 ADS1x31REF; 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. 22 ADS1131REF and ADS1231REF SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Appendix A www.ti.com 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 ADS1x31REF are shown in Figure 9 through Figure 12, respectively. Schematics for the ADS1x31REF are shown in Section A.3. The bill of materials is provided in Table 9. A.1 Bill of Materials NOTE: All components should be RoHS compliant. Some part numbers may be either leaded or RoHS. Verify that purchased components are RoHS compliant. Table 9. ADS1x31REF Bill of Materials Item No ADS1131 ADS1231 Ref Des Description 1 1 1 Value BT1 (+) 9 Volt Battery Clip Female Keystone Electronics 594 2 1 1 BT1 (–) 9 Volt Battery Clip Male Keystone Electronics 593 3 4 4 22pF C1, C2, C16, C17 50V Ceramic Chip Capacitor, ±5%, C0G TDK C1608C0G1H220J 4 4 4 100pF C29, C30, C31, C32 16V PPS Film Chip Capacitor, 2% Panasonic ECH-U1C101GX5 5 4 4 100pF C40, C41, C42, C43 Filter High Frequency, 100pF Murata NFM21CC101U1H3D 6 5 5 0.01μF C5, C11, C13, C14, C15 50V Ceramic Chip Capacitor, ±10%, X7R TDK C1608X7R1H103K 7 6 6 0.1μF C12, C21, C33 to C36 50V Ceramic Chip Capacitor, ±10%, X7R TDK C1608X7R1H104K 8 2 2 0.1μF 16V PPS Film Chip Capacitor, 2% Panasonic ECH-U1C104GX5 9 3 3 1μF TDK C1608X7R1C105K 10 5 5 1μF C37, C38, C39, C44, C45 Filter High Frequency, 1.0μF Murata NFM21PC105B1C3D 11 6 6 2.2μF C23 to C28 6.3V Ceramic Chip Capacitor, ±20%, X5R TDK C1608X5R0J225M 12 1 1 4.7μF C3 16V Ceramic Chip Capacitor, +80/–20%, Y5V TDK C2012Y5V1C475Z 13 4 4 10μF C8, C18 to C20 16V Ceramic Chip Capacitor, ± 20%, X7R TDK C3216X7R1C106M 14 1 1 100μF C4 10V Tantalum Chip Capacitor, ±10% Kemet T494D107K010AT 15 1 1 D1 30V, 200mA Schottky Diode Fairchild Semiconductor BAT54 16 1 1 D2 Green LED, SMD Lumex SSL-LX3052GD 17 1 1 J1 USB Type 'B' Socket Mill-Max 897-43-004-90-000000 18 1 1 J2 2.5mm Power Jack CUI PJ-102BH 19 0 0 J3 2 X 7 Header 20 1 1 J6 1 X 6 Header Samtec TSW-106-07-G-S 21 2 2 J7, J8 1 X 2 Header Samtec TSW-102-07-G-S 22 1 1 J4 3.5mm PCB Terminal Block, 4 position On Shore Technology ED555/4DS C6, C7 C9, C10, C22 16V Ceramic Chip Capacitor, ±10%, X7R SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Vendor Part Number Schematic and Layout 23 Bill of Materials www.ti.com Table 9. ADS1x31REF Bill of Materials (continued) Item No ADS1131 ADS1231 23 1 1 Ref Des Description J5 3.5mm PCB Terminal Block, 2 position On Shore Technology ED555/2DS 24 1 25 1 1 L1 Ferrite Bead Core, 4A 100MHz Panasonic EXC-ML20A390U 1 LCD1 8 Character LCD Display, Reflective Type Varitronix VIM-878-DP-RC-S-LV 26 2 2 0Ω 27 1 1 20Ω R23, R24 1/10W 5% Chip Resistor Panasonic ERJ-3GEY0R00V R17 1/4W 5% Chip Resistor Panasonic 28 2 2 ERJ-8GEYJ200V 33Ω R2, R3 1/10W 5% Chip Resistor Panasonic 29 4 ERJ-3GEYJ330V 4 100Ω R12 to R15 1/10W 5% Chip Resistor Panasonic 30 ERJ-3GEYJ101V 1 1 220Ω R11 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ221V 31 1 1 1.5kΩ R1 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ152V 32 8 8 10kΩ R4-R10, R16 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ103V 33 2 2 20kΩ R25, R26 1/10W 1% Chip Resistor Panasonic ERJ-3EKF2002V 34 2 2 47kΩ R18, R27 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ473V 35 1 1 200kΩ R22 Potentiometer 200K Ohm 1/4" SQ Bourns 3362U-1-204LF 36 3 3 221kΩ R19 to R21 1/10W 1% Chip Resistor Panasonic ERJ-3EKF2213V 37 6 6 SW1 to SW6 Pushbutton Switch ITT KSA1M211LFT 38 1 1 SW7 DPDT Slide Switch, Top Actuator NKK SS22SDP2 39 1 1 SW8 SPDT Slide Switch, Top Actuator NKK SS12SDP2 40 1 1 SW9 4PDT Slide Switch, RA Actuator E-Switch EG4208 41 0 0 42 1 1 TP15 Testpoint Keystone Electronics 5011 43 1 0 U6 Two-Channel Analog to Digital Converter Texas Instruments ADS1131ID 0 1 Two-Channel Analog to Digital Converter Texas Instruments ADS1231ID 44 1 1 U5 Microcontroller with LCD Drivers Texas Instruments MSP430F449IPZ 45 2 2 U2, U3 Linear Voltage Regulator, +3.3V Texas Instruments TPS77133DGK 46 1 1 U1 Linear Voltage Regulator, +5V Texas Instruments TPS76350DBV 47 1 1 U4 USB to Serial Converter Texas Instruments TUSB3410VF 48 2 2 U8, U9 Digital Isolator Texas Instruments ISO721D 49 2 2 U7, U10 Inverter, Single Gate Texas Instruments SN74LVC1G04DBVR 50 1 1 12MHz X1 Quartz Crystal SMD ECS Inc. ECS-120-20-23B-TR 51 1 1 32.678kHz X2 Quartz Crystal Epson C-002RX 32.7680K-E:PBFREE 52 1 1 N/A ADS1x31 REF PWB Texas Instruments 6517107 53 4 4 N/A 1/4" x .75 hex 4-40 Brass Threaded Standoff Keystone Electronics 1656A 54 4 4 N/A Phillips Machine Screw, 1/2" 4-40 Building Fasteners PMSSS 440 0050 PH 55 2 2 N/A Shorting Block Samtec 24 Schematic and Layout Value Vendor Part Number TP1 to TP14, Not Installed TP16 to TP18 SNT-100-BK-G-H SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated PCB Layout www.ti.com A.2 PCB Layout Figure 9. ADS1x31REF PCB—Top Side Figure 10. ADS1x31REF PCB—Layer 1 SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Schematic and Layout 25 PCB Layout www.ti.com Figure 11. ADS1x31REF PCB—Layer 2 Figure 12. ADS1x31REF PCB—Bottom Side 26 Schematic and Layout SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Schematics www.ti.com A.3 Schematics C30 TP13 100pF TP11 EXTCLK C27 2.2uF +5VA 3 2 13 10 9 7 8 5 6 12 11 C28 2.2uF C45 C31 C42 TP15 GND +5VA C38 TP3 +5V C39 R24 MUR_NFM21PC105F1C3D 0 D1 CUI-STACK PJ-102BH 5 VIN VOUT ENABLE GND NR/ADJUST C8 10uF 4 R26 20K +5VA 1 2 3 4 5 6 +5VA HEADER-6 +5V U1 1 3 2 R23 0 100pF 20K EXC+ EXCSNS+ SIG+ SIGEXCSNSEXC- BT1 J2 C7 0.1uF C29 R25 J6 9V J8 1 PWDN PDWN TP12 SPEED SPEED TP10 SCLK SCLK DOUT TP9 100pF MUR_NFM21PC105F1C3D J7 DOUT SW-DPDT 100 C6 0.1uF C43 TP6 +5VA 2 C41 SW7 C32 ADS1231ID ADS1131ID (GND PIN 3) C40 VREF+ 100 100pF 1 R27 47K DVDD AVDD SPEED VREFP SCLK VREFN DRDY/DOUT AINP PDWN AINN CAP CLKIN CAP GND PSW GND R14 TP14 C4 100uF VREFR15 2.2uF U6 1 4 15 16 14 C44 2 +3.3VD C26 J4 J5 OST_ED555/4DS OST_ED555/2DS C19 10uF TPS76350DBV C11 0.01uF TP4 +3.3VD +5VA C9 1uF +3.3VD U2 5 6 3 4 IN OUT IN OUT EN FB/SENSE GND RESET 7 8 1 2 RST C20 10uF TPS77133DGK Figure 13. ADS1x31REF Schematic—ADC SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Schematic and Layout 27 Schematics www.ti.com +3.3VD SW2 SW3 RANGE SW4 TARE SW5 CAL CONFIG C13 C14 C15 C5 0.01uF R19 0.01uF R20 0.01uF R21 0.01uF 221K 221K 221K R8 10K R9 10K +3.3VD SIMO0 R22 200K PDWN C23 2.2uF COM(3) COM(2) COM(1) COM(0) S(39) R7 10K DOUT SCLK SPEED TP18 TP8 MCURX MCUTX 10K R10 TP7 DNP 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 MCURX MCUTX J3 2 4 6 8 10 12 14 TDO/TDI TDI/CLK TMS TCK 1 3 5 7 9 11 13 C25 2.2uF RST +3.3VD 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) 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) LCD1 LCD_DISPLAY U5 MSP430F449IPZ S(5) S(6) S(7) S(8) S(9) S(10) S(11) S(12) S(13) R18 RESET 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 HEADER-7X2 SW6 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 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 R13 100 R12 100 +3.3VD P4.3/SIMO1/S38 P4.4/SOMI1/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 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 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/SMCLK P1.3/TBOUTH/SVSOUT P1.2/TA1 P1.1/TA0/MCLK P1.0/TA0 XT2OUT XT2IN TDO/TDI TDI/TCLK TMS TCK RST/NMI P6.0/A0 P6.1/A1 P6.2/A2 AVSS DVSS1 AVCC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 76 77 78 79 80 81 82 83 84 85 86 BSLRX 87 BSLTX 88 89 90 91 92 93 94 95 96 97 98 99 +3.3VD 100 DOUT 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) R16 10K TP5 P1.4/SMCLK RST TCK P2.4/UTXD0 P2.5/URXD0 P2.6/CAOUT P2.7/ADC12CLK P3.0/STE0 P3.1/SIMO0 P3.2/SOMI0 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/COM3 P5.3/COM2 P5.2/COM1 COM0 P4.2/STE1/S39 +3.3VD SW8 NKK_SS12SDP2 47K C24 2.2uF X2 EPS_C-002RX 32.7680K-A:PBFREE Figure 14. ADS1x31REF Schematic—MCU C33 TP16 RX USB3.3V 1 3 2 4 R5 TP17 TX C22 C34 R2 33 R3 33 C16 22pF C17 22pF 3 25 4 VCC VCC CTS RTS RI/CP DTR DSR DCD PUR DP DM GND GND GND TEST0 TEST1 R17 20 VCC2 VCC1 OUT VCC1 GND2 IN GND2 GND1 C36 0.1uF MCUTX C12 U10 4 SN74LVC1G04DBV PROGRAMMING MODE SW9 23 24 USB3.3V U7 2 TCK C21 0.1uF 4 RST SN74LVC1G04DBV +5VA 32 31 30 29 4 3 2 1 USB5V +5V SW1 ESW_EG4208 USB RESET USB5V USB SLAVE CONN C37 MUR_NFM21PC105F1C3D C3 4.7uF USB3.3V U3 5 6 3 4 IN OUT IN OUT EN FB/SENSE GND RESET 7 8 1 2 R6 C18 10uF TP2 3.3V_USB GND D+ DVCC +3.3VD 1 3 2 4 0.1uF 2 TUSB3410VF 1 9 2 12 J1 USB3.3V 19 RX 17 TX USB3.3V 13 20 RTS 16 21 DTR 14 15 5 SOUT/IR_SOUT SIN/IR_SIN MCURX ISO721D 3 VDD SCL SDA CLKOUT 8 6 7 5 U9 8 6 7 5 3 R1 1.5K 8 18 28 X2 X1/CLKI 5 5 6 7 FERRITE BEAD L1 1uF P3.0 P3.1 P3.3 P3.4 22 C2 22pF 12MHz USB3.3V 0.1uF U4 26 27 VREGEN RESET SUSPEND WAKEUP C1 22pF 10 TP1 USB_CLK 11 10K 10K X1 VCC1 VCC2 VCC1 OUT IN GND2 GND1 GND2 C35 0.1uF ISO721D USB3.3V R4 +3.3VD U8 0.1uF 10K R11 220 C10 1uF TPS77133DGK D2 GREEN Figure 15. ADS1x31REF Schematic—USB 28 Schematic and Layout SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Revision History www.ti.com Revision History Changes from Original (July, 2010) to A Revision .......................................................................................................... Page • • • • • • Deleted references to Offset Calibration in Table 2 .................................................................................. 9 Removed information on Offset Calibration from Section 2.4.1 .................................................................. 10 Deleted information about Offset Calibration from Table 5 ........................................................................ 13 Removed information about Offset Calibration from Section 3.4.1 ............................................................... 13 Updated Table 6 to remove Offset Calibration information ........................................................................ 19 Deleted Offset Calibration section from Command Reference section .......................................................... 19 NOTE: Page numbers for previous revisions may differ from page numbers in the current version. SBAU175A – July 2010 – Revised August 2011 Submit Documentation Feedback Copyright © 2010–2011, Texas Instruments Incorporated Revision History 29 Evaluation Board/Kit Important Notice Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by TI to be a finished end-product fit for general consumer use. Persons handling the product(s) must have electronics training and observe good engineering practice standards. As such, the goods being provided are not intended to be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety and environmental measures typically found in end products that incorporate such semiconductor components or circuit boards. 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