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Original question:

TPS65981: Probing for the TPS65981 PD Controller on the I²C bus using SMBus Quick commands

TPS65981: Reading TPS65981 ADCs over I²C

Andrew Royal
Prodigy 70 points
Part Number: TPS65981

Hi,

I'm trying to read the TPS65981 ADCs over the I²C bus and after looking at the Host Interface Technical Reference and the Datasheet I'm still confused on a few things:

  1. I'm not entirely sure how the command interface works.
    1. I think I have to write the Input DataX to the data register before writing the command to the cmd register - is that correct, or should input data be written after the command?
    2. Once the cmd register reads back all zeroes, the data register appears to still contain the input data followed by output data. I was expecting the input data to be replaced by output data. Am I accidentally overwriting the output or should I expect the the input data to be echoed in the output?
  2. The datasheet mentions three different modes for ADC access.
    1. How can I switch between the three modes - single-channel, round-robin and automatic?
    2. Which registers contain the output of the automatic readouts?

Thanks
Andy

  • 0
    TI__Expert 4415 points

    Hi Andy,

    Here are my answers for your questions:

    1. a: Yes, you are correct. The Input DataX should be written before command.

        b: The Output DataX will store the  conversion result when the cmd register reads back all zeroes, the Input DataX is the ADC channel you wrote before command.

    2. Round-robin and automatic modes are reserved for GUI only, and they cannot be used for users. Single channel is the only mode for users.

    I hope this helps and If this answers your question, PLEASE select  This resolved my issue  

    Hao

  • 0 in reply to Hao Wang14
    Prodigy 70 points

    Thank you Hao, that has answered all of my questions.