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ADS1299: Can I connect CS signal to GND when I use only one AD device

YAN LI
Prodigy 100 points
Part Number: ADS1299

Hi,

I think my master SPI CS pin can not match the time delay request of ADS1299 so that I have a communication problem, I can't get any info from the ADS1299. So, I connect the CS pin to GND, then the communication work well. So I want to know whether I can connect the CS pin to GND(or low GPIO) when I have only one AD device.

Looking forward to your help.

Yan

  • +1
    TI__Genius 11550 points

    Hi Yan,

    Thanks for the post. 

    You can set the CSB pin to low if you are not sharing the SPI with any other devices. 

    Thanks

    -TC

  • 0 in reply to TCT
    Prodigy 100 points

    Hi TC,

    Thanks for your replay.

    Another question follow the question is If I keep CS low,  and ,  there is a noise of SCLK signal in a un-transfer period  and make SCLK abnormal，will ADS1299 recognize this noise as SCLK signal. In the transfer period, I find in datasheet as below, says if SPI in a abnormal state, the CS should pull high to cover.

    So if I keep CS low, when something wrong in the SCLK, will these impact the following sample data?

    If the noise only impact the time abnormal, I think keep CS low is ok.

  • +1 in reply to YAN LI
    TI__Genius 11550 points

    Hi Yan,

    One of the disadvantages of keeping the CSB low permanently is noise immunity for the SPI bus. Any noise in the SCLK signal may cause the SPI bus to be in an unknown state or unable to decode the proper command. In addition, it may cause corruption on the sample data as well. Therefore, either issue a device RESET or pull the CSB high to reset the serial interface during this condition.

    Thanks

    -TC

  • 0 in reply to TCT
    Prodigy 100 points

    TC,

    Thanks a lot, the conclusion is if I keep CS LOW, I will face the risk of SPI communacation.

    I will consider how to deal with it.

    Best wishes!

    Yan