ADS7950: GPIO output configuration problem

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Replies: 5

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Part Number: ADS7950

Hi team,

According to ADS7950 datasheet, 4 GPIO pins can be configured as general purpose I or O. But the customer writes 0x400c to the register (GPIO3 is configured as output); then writes 0x1818 to the register (Manual Mode + GPIO3 output is 1), the ADS7950 has no response. What reason is this? Could you give some advice?

Best Regards,
Amy Luo

5 Replies

  • Hello,

    The command 0x1818 seems to be correct to sample channel 0 and set GPIO3 high.

    I predict this means that the GPIO was likely not set correctly. Section 8.5.2 GPIO registers of the datasheet explain show to do this.

    I suggest trying the following:

    0x4200h this will reset all the GPIO register settings

    0x4008h this will set GPIO3 as output

    Also remember that this device has a 2 cycle delay. meaning that in FramenN you set GPIO3 high, but you will not see it until Frame n+2.

    Regards

    Cynthia

  • In reply to Cynthia:

    Cynthia:

    Hi,

    We send 0x4200 as you said, then send 0x4008/0x400C, then send 0x1818, but GPIO3 still dosen't work....

    Do you have a successful example of configuring the GPIO of the ADS7950 to be an output pin through SPI?
    Regards
    Yan
  • In reply to user5278687:

    Yan,

    There is no sample code available

    Would you share a scope shot with the digital lines probed on the oscilloscope?

    This will about 6 frames, the first half to set the GPIO, and the second to get the conversion data, as it take 2 frames after the initial conversion for valid data out.

    Be sure to use a known DC input at the ADC input to be able to compare expected vs actual

    This will help verify timing as well as the digital lines showing correct communications

    Regards

    Cynthia

  • In reply to Cynthia:

    Cynthia:

    Okey...

    But, I will share with you a scope shot with the digital lines probed on the oscilloscope next Monday.
    Regards
    Yan
  • In reply to Cynthia:

    Cynthia:

    Thank you very much for reminding!

    We checked the SDO of the ADS7950 and found it advance SCLK one phase, so we reconfigured the SPI phase control register of the controller DSP.
    The result is successful!The output of GPIO3 matches expectations.


    Thank you again!
    Regards
    Yan