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ADS131M02: writing register

Jonathan Navor
Genius 9475 points
Part Number: ADS131M02
Other Parts Discussed in Thread: ADS131M04

Tool/software:

Hi Experts,

Customer is able to read from the chip, via SPI. They can validate the data coming out and it all looks good. But they are having trouble writing to registers. Specifically, they are trying to change the data rate from the default 4kSPS to a higher number, say 8kSPS. 

My first question is if I am correct in my understanding that the OSR bit needs to be updated to change the data rate, and that it is the only thing controlling the data rate. 

Assuming so, could you help me with a sample communication frame of what that may look like? 

I am sending it 4 words, first the WREG (01100001 10000000 00000000), second data word (00000011 00001010 00000000) followed by 2 empty words. I have verified that it gets transmitted accurately w/ a logic analyzer.  

For clarity, I am looking at the ADS131M02, which does not have the config 1 register. 

Could you share with me exactly what the communication frame (including the exact words in binary), I need to use the WREG command, and update the OSR bit, to sample at 16KSPS for 8.192MHz clock - table 8-2 from datasheet).

The goal is to compare the bit-math and frame and see why I cant update the register. My hunch is that data word (second word) is incorrect.

Thanks for your help, 

  • 0
    TI__Mastermind 38425 points

    Hi Jonathan,

    Yes, the OSR configuration is used to change the output data rate. This is the only change which should be done to change the data rate except the master clock.

    The customer's WREG command is correct and the data "10" is also correct to change the data rate.

    See the following timing example for ADS131M04 (4-ch ADC) to write the CLOCK register with 0F0Eh data in the 1st frame and the response from the ADC can be seen in the 2nd frame. Note that it is not necessary to send all the rest of words to the ADC for reading or writing a register if /CS signal is used. 

    To change the data rate to 16ksps, the WREG command+data to ADS131M02 should be:  WREG (01100001 10000000 00000000)+data word (00000011 00000110 00000000).

    If the customer still has a trouble after they look at my timing, please provide the customer's timing plot.

    BR,

    Dale