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ADS8201: How to read ADC from ADS8201

Tam hoag
Prodigy 70 points
Part Number: ADS8201

Dear all,

Now I use ADS8021 to read ADC value by SPI communication.

I send : 0x9004 (select channel 4)

I send : 0x0000 (begin to read adc)

I read that: 0x0000 0x8000 for 0V

I read that : 0xFF70 0x8000 for 3V3

I don't know it is true or false and how to convert 0xFF70 0x8000 to adc value?

Anyone know sequence to read adc value(configure + read)

Thanks and best regards.

  • 0
    TI__Guru**** 172846 points
    Hi Tam!

    Welcome to our e2e Forum! Can you give us a little more detail on how you are using the ADS8201? What is your reference voltage and your PGA setting? You can review Table 6 on page 16 to get the basics on how to convert code to voltage. If I were to assume that your reference is 3.3V, your LSB size would be 3.3 V/4096 Codes or about 805 uV/Code. Your 0xFF70 would be 4088 codes * 805 uV or about 3.29 V.
  • 0 in reply to Tom Hendrick
    Prodigy 70 points
    Dear Tom,

    Thanks for your hint.

    In my side,
    //==========Hardware==========
    REF = VA = VD = 3,33V;
    ADCIN = AGND = REFGND = 0V;
    PGAOUT = PGAREF = 0V;

    //===========Software==========
    //Hardware Reset
    RST = 0;
    delay_us(1);
    RST = 1;

    //set to Idle Mode
    Write 0x00 to Register 0x08;

    //select channel 6
    Write 0x06 to register 0x04;


    While(1)
    {
    ReadADC(); //I read adc by sending 0x0000 0x0000 using SPI(MODE 0, MSB First)
    Delay(1s);
    }

    I see that:
    > with 0V, I read 0x0000
    > with 2V, I read 0xFF70 0x8000.
    > I increase from 2V to 3v3, it still 0xFF70 0x8000.

    I don't know what problems.
    May you suggest me a configuration for reading ADC from a single chanel and multiple single also.

    Thanks And Best Regards,

    Tam
  • 0 in reply to Tam hoag
    TI__Guru**** 172846 points
    Hi Tam,

    Please use SPI Mode 1 (CPOL = 0, CPHA = 1) and provide some screen shots of you commands/data responses (/CS, SDI, SDO and SCLK) and a schematic of your ADC front end signal chain.
  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Dear Tom,

    Spi mode 1 doesn't work. we have to use spi mode 0.

    Best Reagards,

    Tam

  • 0 in reply to Tam hoag
    TI__Guru**** 172846 points
    Hi Tam,

    So, are you still having issues? Can you send along screen captures of your read/write sequence to the ADS8201?
  • 0 in reply to Tom Hendrick
    Prodigy 70 points
    Hi Tom,

    Finally, I find my issue. My Vref = 2.5V. So I just read adc value <= 2.5V
    I increase Vref to 3.3V. It's OKE.

    Thanks for your support
    Best Regards,
    Tam