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AM335X ADC pin can be used as GPIO

Manoj Agarwal
Expert 1030 points


Can unused ADC pin of AM335X can be used as GPIO. I found that it can not be used and want to confirm the same.

  • 0
    TI__Guru**** 393215 points
    No, ADC input pins cannot be used as GPIO.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru 63205 points
    I would like to clarify Biser's comment. He is correct the ADC inputs cannot operate as general purpose input/output, but the touch screen controller can be configured such that some of the ADC inputs can be used as outputs. See notes 20, 21, and 22 of the Pin Attributes table in the AM335x data sheet. Also refer to the Touch Screen Controller chapter in the AM335x Technical Reference Manual. In the TRM, you can see a schematic representation of how the ADC inputs can be used as outputs in the Analog Front End (AFE) Function Block Diagram.

    Regards,
    Paul
  • 0 in reply to peaves
    Expert 1030 points

    Hi Paul,

    I want to again clarify that ADC pins(AIN0 to AIN4) can be used as open drain output . So in our design we can put external pull up resistor on these pins and can use them as output. Is this understanding correct?

     

    Regards

    Manoj A

  • 0 in reply to Manoj Agarwal
    TI__Guru 63205 points
    No, AIN[0] cannot be configured as open-drain.

    AIN[0] can be configured to operate as open-source.
    AIN[2:1] can be configured to operate as open-source or open-drain.
    AIN[4:3] can be configured to operate as open-drain.

    The Touch Screen Controller ADC (TSC_ADC) must be used to configure these terminals as outputs. The output functions provided on these terminals were designed to apply a voltage across a resistive touch screen while one of the other AIN terminals is used to measure the voltage divider output when someone touches the screen. So these outputs can be turned on while executing one of the ADC steps. However, this limited function of only being turned on while executing a step may not work for your application.

    You need to read the TSC_SDC chapter in the AM335x TRM to understand how these outputs are controlled and determine if the limited function they provide will work for your use case.

    Regards,
    Paul