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ADS8588S: ADS8588S: Issue in first sample

Nilesh patel
Prodigy 10 points

Part Number: ADS8588S

Hi Ti team,

I have selected four ADS8588S to interface 32 sensor data reading simultaneously.

I read data from the adc in parallel mode.

ADC READ procedure that I follow:

    Step-1 :

                Set CONV pin to high.

     Step -2

                Check Busy signal (wait for busy signal to low).

     Step -3

                Set CS pin to low.

     Step -4

               Set RD pin to low.

               Read Data from GPIO pins.

               Set RD pin to HIGH.

               (Step -4 procedure repeat for all 8 chanel)

      Step - 5

               Set CS pin to HIGH.

      Step - 6

              Set CONV pin to low.

     ( These all steps repeat for all the 4 ADCs, 32 -channels )

Issue:

In first sample of all the adc, have some garbage value or some time 0 value.
but from 2nd sample onward, all the data are as expected.

  • 0
    TI__Guru 50025 points

    Hi Nilesh,

    I will get back to you soon, thanks.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 500 points

    Hi Dale,

    Adding more details to the above question shared by Nilesh,

    We have designed our custom board with four ADCs of ADS8588S to get sync all 32 channels data from the sensor input .

    Our interfacing is as per below,

    - All four ADCs(A,B,C,D respectively) CONVST signal is common and connected to processor,

    - 32 pins of processor shared with two ADCs A,B(0-15) and C,D(16-32)

    - Chip select(CS), RD, is shared with AC and BD ADCs.

    Means we are doing parallel operation of two ADCs A and B at same time to get better sampling rate. Here we are achieving sampling rate and also receiving expected data in sync.

    But When start ADC to capture data, first sample of all the ADCs, have some garbage value or some time 0 value so can you please help to resolve this issue?

    waiting for your response

    Thank you,

    Nilav.

  • 0 in reply to Nilav Choksi66
    TI__Guru 50025 points

    Hi Nilav,

    I apologized for late response. I'm a little confused about your connection, usually the /CS is used to select different ADC, however your AC or BD ADCs are sharing same /CS also CONVST signal, how do you read the data per device? a schematic is helpful for me to understand, you can contact me by friendship on the forum and share it to me if you want. 

    Also, have you checked the first data only with one ADC? This ADC is a precision ADC with integrated AFE including ADC driver, so this should not be an issue caused by signal settling on sampling and hold capacitor on internal ADC which is different from universal switch-capacitor input structure SAR ADC.

    Thanks&regards,

    Dale