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ADS7957-Q1: ADS7957 Development Guide

Alan Xia
Expert 7605 points
Part Number: ADS7957-Q1
Other Parts Discussed in Thread: ADS7957

Hi team，

At present, the customer project uses the ADS7957 solution to read the AD sampling value. After reading the "ADS7957-Q1.pdf" specification, the customer only saw how to write some configurations through SPI, but it was not very clear how to obtain the read operation of the AD sampling value. Is it enough to read a null value (0x00 or 0xFF) through SPI, or do I need to read a specific register?

  • 0
    TI__Guru**** 176421 points

    Hi Alan,

    Please refer to Figure 45 in the datasheet.  Conversion data is presented on the SDO pin as you write to the ADS7957.  There are no 'null values' associated with the ADS7957, once you have the device configured, you write 0x1000 to SDI to remain in the desired configuration.  If you are in manual mode, you need to add CHx detail to the command (see page 27).

  • 0 in reply to Tom Hendrick
    TI__Expert 7605 points

    Hi Tom，

    Thanks for your help！

    The customer did not see the detailed description of the SPI basic configuration in the ADS7957 specification, and is worried that there may be errors in the SPI related configuration. I would like to confirm the following points with you:
    The polarity of SPI (CPOL), the phase of SPI (CPHA), and how long after the ADS7957 is powered on, can the SPI be initialized?

  • 0 in reply to Alan Xia
    TI__Guru**** 176421 points

    CPOL = 0 (clock is inactive low) and CPHA = 0 (valid data on rising clock edge).  You can start talking to the device once all supply rails are stable.