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ADS1258 wrong ID code

Babu9307
Intellectual 340 points
Other Parts Discussed in Thread: ADS1258, ADS1158

I am working with ADS1258.  On many of my boards having ADS1258, I get device ID as 0x8B, and I read back the register values same as what I wrote. 

But recently, some boards gave me values such as 0x3F, 0x7F.  And I do not read back the same values from registers that I wrote.

Any hints, suggestions? (You think board HW may have changed, or SPI is not working right or What?)

Babu

 

  • 0
    TI__Guru**** 180941 points

    Babu,

    The ADS1258 ID code should be 0x8B.  As noted in the 'Wrong ID Code' posting of the ADS1158, this internal code is subject to change.  You also say that you are getting the 0x3F or 0x7F codes in the following conditions:

    • case 1: When we have the RC filter, then my code reads the ADS ID correctly, and all measurements are fine.
    • case 2: For testing we took out capacitor, leaving resistor.  Now the same code does not read the ADS ID correctly.

    If the RC Filter is on the SPI clock or data lines, you may simply be reading data on the wrong clock edge.  The added RC may be slowing down edges so that your processor is able to correctly interpret the data.  If this RC is on the analog input, there is no reason for you to be having any trouble at all.  The device ID bits are from an internal fixed register and they have nothing to do with the analog input.