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ADS131M08: Help to check SPI question

Jessica Wu74
Expert 6010 points
Part Number: ADS131M08

Hi Team,

Could you please kindly help to check if customer below SPI data is correct? Relate command should read 01h data(from cursor a to cursor b), default read back value should be 0500h, but from below purple waveform, it seems no any feedback from our device. 

Yellow: SCLK; Blue:DIN; Purple: Dout;  CS pull low(not captured by customer) during there has clk.

Below is customer SPI mode configuration:

word size: 16bits; Full duplex;MSB; clk speed: 281khz; CS control by software; CPOL=1; PHASE  at the second clk rise edge, master mode. 

And customer use GPIO to simulate the spi communication, could your team possible help to check if customer above SPI mode is correct to communicate with our device? And could you possible help t provide the correct SPI mode configuration for customer, it will be better if there has a reference code which could provide to customer for reference.

Thanks a lot for your support.

Best regards

Jie

  • 0
    TI__Mastermind 45805 points

    Hi JIe,

    The customer should not expect to see the response (register data) from ADS131M08 ADC in the same frame as the frame for sending the RREG command. Below is the RREG timing shown in the ADC datasheet. The command is sent in the 1st frame and the register data is shifted out from the ADC in the 2nd frame (first word). I also attached a correct timing which was captured on our EVM, it can be a good reference for the customer.

    Also, the correct SPI configuration is CPOL=0, CPHA=1, so the data can be captured on the falling edge of SCLK. 

    ADS131M08 datasheet has provided an example code, see the section 9.1.6 Code example in the datasheet. Also, the customer can download the example code (SBAC254.zip) under Software development under ADS131M08 product folder on TI.com. 

    Let me know if the customer still has any question.

    Timing for reading a single register:

    Timing captured on the EVM (reading CFG register):

    Code example location on TI.com:

    BR,

    Dale