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Original question:

ADS131A04EVM: ADS131A04

ADS131A04: ADS131A04

miao deng
Prodigy 10 points

Part Number: ADS131A04

Tool/software:

Hello, I have recently been using the ADS131A04EVM for measuring weak voltages, with MCU being an STM32F407VET6. Below are my relevant register configurations: 

ADS13_REG(WREG|A_SYS_CFG, 0X78); //enable internal reference volatage (4.0v)
ADS13_REG(WREG|D_SYS_CFG, 0X3E); //Fixed six device words per frame for the ADS131A04 
ADS13_REG(WREG|CLK1, 0X08); //ADC CLK1  fICLK = fCLKIN(16.384Mhz) / 2 
ADS13_REG(WREG|CLK2, 0X21); //fMOD = fICLK / 2  fICLK = fCLKIN / 2048 ****** now is 500hz *****0x21
ADS13_REG(WREG|ADC_ENA, 0X0F); //ADC CHANNEL ENABLE ALL

with M0 and M1 are connected to 3.3V, and M2 is connected to GND.

The test signals are generated using a SIGLENT signal generator, and I have also verified the output using a KEYSIGHT oscilloscope. The DC voltage levels appear to be correct, but the measurement results seem to have a significant deviation. Could you please advise on what possible reasons there could be for this?

  • 0
    TI__Mastermind 49465 points

    Hi miao deng,

    Welcome to the TI E2E forum.

    Did you measure these signals with the PHI controller card in the EVK-Kit and the EVM GUI software? If so, please share the data.

    Can you provide more information about your test?

    • Connections between ADS131A04EVM and STM32F407VET6 board
    • Power supplies to ADS131A04EVM
    • Jumpers on the ADS131A04EVM
    • Analog input connections from your signal generator to the ADS131A04EVM

    Your timing plot including SCLK, DOUT, DIN, /DRDY and /CS will be helpful.

    BR,

    Dale

  • 0 in reply to Dale Li
    Prodigy 10 points

    Hi Dale：

    I did not use the PHI controller card and EVM GUI software for measurements. Instead, I used DuPont lines to establish the connection between the ADS131A04EVM and the STM32F407VET6 board. I used the JP1 and JP2 jumpers, and selected 'unipolar' for JP3. The power supply section uses a linear voltage regulator to power both the microcontroller and the EVM. By observing the oscilloscope, the voltage at the EVM 5V input is 4.90V, and the IOVDD voltage is 3.14V. The analog input from the signal generator to the ADS131A04EVM is connected as shown in the figure below.

  • 0 in reply to miao deng
    TI__Mastermind 49465 points

    Hi miao deng,

    I believe you will be able to get a good measured result if you use the PHI controller card and TI EVM GUI software with the EVM board together. With the long wire connection like your setup, a precise measurement should not be expected, however the difference of the measured voltage should not be so large. I would suggest you to do the following test step by step

    1. Remove JP2 to disconnect the external voltage reference (U1) because you already wrote the register to enable the internal voltage reference.
    2. Check your ground connection, use as short wires as possible for signals and ground connection.
    3. Tie the M2 pin to GND for 24-bit word size instead of 32-bit word size to make the debug simple. 
    4. Short the ADC's input on J1/2/3/4 and check the measured data.
    5. While shorting the input or applying a precision DC signal, capture the timing on the J7 connector including SCLK, DOUT, DIN, /DRDY and /CS with a logic analyzer.

     Let me know your test result.

    BR,

    Dale