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CCS/ADS1158: ADC1158 occasional configuration/SPI communication failure; no activity on MISO signal from ADC

Shrikrishna K
Prodigy 100 points
Part Number: ADS1158

Tool/software: Code Composer Studio

Hi,

We have interfaced ADC1158 to TM4C1292. We have identical 10 boards.

On two of the boards, we are not getting reply from ADC to controller (MISO) when we tried to read back the register data after initializing.

This is occasional, and if the board is powered ON repeatedly, error not repeated (Able to successfully configure ADC). If the board is turned ON after some delay, error persists.

Using internal clock with 32.768KHz crystal.

AVDD = 5V

DVDD = 3.3V

Vref = 5V

Is it something related to ADC initialization? 

Have tried below initialization sequence:

1. Resetting ADC and making START pin low and then configure registers

2. Reset ADC, Reset SPI (By pulling CS low), making START pin low and then configuring registers

Is there anything I am missing out here?

Thank you

Krishna

  • 0
    TI__Mastermind 44680 points

    Hi Krishna,

    I would check to see if the crystal is properly starting up. If the load capacitance is off and/or if there is too much parasitic impedance on the crystal connections, it could prevent the crystal from oscillating, and as a result the ADC would not be functional.

    Otherwise, if the device is powered up, the /PWDN pin set high, and the START pin set high, you should see the /DRDY pin pulsing. To be sure that the part is active before you begin communicating with it, you could wait until /DRDY goes low before sending your first command. This way you know that the oscillator is active and stable, and that the device is ready for SPI communications.

    Best Regards,
    Chris

  • 0 in reply to Christopher Hall
    Prodigy 100 points
    Hi Chris,

    Thank you for quick reply.

    I have checked crystal and it is coming up properly with around 350mS delay. I have incorporated 500mS delay before I communicate to ADC.

    As you suggested, I set /PWDN pin set high, and the START pin set high; I see /DRDY pin pulsing on a good working board.
    But on a problematic board (2 out of 10), I see /DRDY pin not pulsing (Stays high).
    Do you suspect anything with chip failure?


    Thank you
    Krishna
  • 0 in reply to Shrikrishna K
    TI__Mastermind 44680 points

    Hi Krishna,

    Sorry for the delay.

    Do you have any current limiting on your power supply? That could potentially cause issues during power-up...

    Other than that I would double check that all supplies are present, and look for any soldering issues that could be causing a bad connection. If none of those issues are present, then you might have a damaged device and I would try replacing it to see if that resolves the problem.

    Best Regards,
    Chris

    UPDATE: This issue has been resolved. The problem appeared to be a soldering issue where certain pins were not completely soldered down. Reworking the PCBs appears to resolve the problem.