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[FAQ] ADS129x: What are the correct polarity and phase (CPOL, CPHA) SPI settings?

Alexander Smith
Guru 51051 points
Other Parts Discussed in Thread: ADS1293

I'm having some trouble communicating with my ADS129x device, what SPI settings should I be using? 

  • 0
    TI__Guru 51051 points

    Most devices in the bio-potential family (all except ADS1293) use SPI Mode 1. This means the clock polarity (CPOL) = 0 and the clock phase (CPHA) = 1. The host MCU acts as the master controller, while the ADS129x device acts as the slave. The rising edge of SCLK is used to shift the data and the falling edge is used to latch the data. When we are not communicating with the slave, we want SCLK to idle low. 

    The ADS1293 uses an interface that is different from the rest of the ADS129x family. For the ADS1293, data is changed on the SCLK falling edge and latched on the rising edge. This corresponds to SPI Mode 0, which means CPOL = 0 and CPHA = 0.

    The figure below summarizes the four SPI modes for your reference:

    Link to BIOFAQ homepage

    This post applies to ADS1191, ADS1192, ADS1291, ADS1292, ADS1292R, ADS1293, ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R,

    ADS1299-4, ADS1299-6, and ADS1299.