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ADS1260: SPI DOUT not echoing

THOMAS WALTER
Prodigy 160 points
Part Number: ADS1260


Tool/software:

Hi,

I am using the ADS1260BIRHBT on my board.

I want to communicate with it with SPI.

I think I did all right : CPOL = 0,  CPHA = 1, reset/ PIN is high.

When I try to write a register (0x46 for instance), the chip doesnt echoes first byte (address = 0x46):

I got the same behaviour when I try a read (0x20 address).

What am I missing ?

Thanks

  • 0
    TI__Guru 53506 points

    Hi THOMAS WALTER,

    If you pull the START pin high and probe the DRDY pin, do you see the DRDY pin pulsing at approximately 1/data rate? For example, if you perform this check after startup or reset when the ADC registers are set to their default values, the ADC will be operating at 20 SPS. Therefore you should see DRDY pulses approximately every 50ms. This will at least tell you if the ADC is powered properly and the clock is working correctly.

    Can you provide a schematic so we can review?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 160 points

    Hi,

    Thanks for your answer.

    Start pin is tied low as we intend to control this via SPI START command.

    Clkin is tied low as we intend to use internal oscillator.

    See attached schematic:

  • 0 in reply to THOMAS WALTER
    TI__Guru 53506 points

    Hi THOMAS WALTER,

    If you send the START command then, do you see DRDY pulsing?

    Can you enable the CRC so you can compare your calculated results to the ADC output? This will help you confirm if the ADC is receiving your commands correctly as well

    You have a pulldown on the RESET pin instead of a pull-up. Are you making sure to pull this pin high before communicating with the device?

    -Bryan

  • +1 in reply to Bryan Lizon86
    Prodigy 160 points

    Hi,

    Thanks for your answer.

    Yes, the RESET pin is correctly pulled up before communicating.

    After some try hard I finally have it to work but I can't say how at this moment.

    Last question: is there a min/max time between two bytes ?

  • 0 in reply to THOMAS WALTER
    TI__Guru 53506 points

    Hi THOMAS WALTER

    There is not a minimum time between bytes within the same command

    I would also recommend toggling CS after each command to reset the SPI interface, this is the most robust communication method

    -Bryan