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ADS8588S: Reading all 8 channels through DOUTA in serial mode

Chris
Prodigy 10 points
Part Number: ADS8588S

Tool/software:

Good afternoon,

I am looking to use the ADS8588S in serial mode, reading data in using only DOUTA. I might be missing something obvious in the datasheet, but I cannot see how to achieve this in hardware beyond paragraph three of 8.4.2.3.3 in the ADS8588S datasheet:

The ADS8588S can output the conversion results on one or both of the serial data output lines, DOUTA and DOUTB. The conversion results from the first set of channels (channels 1-4 for the ADS8588S) appear first on DOUTA, followed by the second set of channels (channels 5-8 for the ADS8588S) if only DOUTA is used for reading data.

Is this achieved by tying DOUTB to ground, maybe?

As a second question to this, I am doing some testing on the ADS8588SEVM-PDK with a Saleae logic device, and am hoping to achieve the above functionality. Tying DOUTB to GND on the dev board does not achieve the desired effect, with only the first four channels being output on the DOUTA pin. Is it possible to emulate this behaviour on the dev board, or is the way the microcontroller hardware/firmware is set up prohibitive in this matter?

Any advice you can offer would be greatly appreciated.

Best regards,
Chris

  • 0
    TI__Guru**** 181021 points

    Hi Chris,

    Try looking at the first bullet point on page 43 of the ADS8588S datasheet.  If you only use DOUTA, data will come out of the device from CH1 through CH8 in assending order.  If you only use DOUTB, you would get CH5 to CH8 followed by CH1 through CH4 as depicted in Figure 69.

    For your second question, the EVM/GUI are not configured to read from DOUTA only.  And as you saw, shorting DOUTB to ground is not recommended.  All data will be output on BOTH the DOUTA and DOUTB if you were to provide /CS and give 128 SCLK cycles to the ADS8588S.

  • 0 in reply to Tom Hendrick
    Prodigy 10 points

    Hi Tom,

    Thank you for your reply.

    I read through the whole datasheet, including page 43, and nothing is explicit regarding best practices for hardware design. To confirm, it is fine to leave DOUTB floating if only using DOUTA?

    Thank you for confirming the SCLK cycles -  I will proceed with testing that today.

    Best regards,
    Chris

  • +1 in reply to Chris
    TI__Guru**** 181021 points

    Hi Chris,

    Yes, you can leave DOUTB float.