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LAUNCHXL-CC1350: Problem with Sensor Contoller when using ADC and COMPB

Philip Scharf
Prodigy 210 points
Part Number: LAUNCHXL-CC1350

Hi,

I´m facing a problem while using both, the ADC and the COMPB, in my Sensor Controller tasks.

For better understanding, here a brief description of my setup:

Like you see in the picture, i have 2 tasks on my sensor controller, one does some pressure measurement (DIO 23&24) and the other only measures the input of one analog pin (DIO30) with the COMPB and compares it eith an internal voltage. The pressure sensors are, at this time, replaced with potentiometers for testing purpose.

Now to my problem:

When I only run the comparator task, everything works as expected, the DIO30 gets measured, is compared with an intern voltage and i can read the comparator output via scifTaskData.comparator.output.charging in the main program.

When both tasks are activated, it seems like positive input of the comparator is using the value of the ADC, so it doesn´t compare DIO30, but it compares DIO24 (i first measure DIO23 and then DIO24 in the measurement task) with the reference. I think it has something to do with the shared input of the adc and the comparator. It also makes no difference, which task is the first to run.

Is there a way to fix this problem, or do I have to use the COMPA, when using the adc on the Sensor Controller?

  • 0
    TI__Guru**** 317180 points
    If you press F1 in SCS and select COMPB you will get an overview of how the COMPB and the ADC are connected internally. As you can see the input on ADC and COMPB is connected.

    The COMPB is typically used to check if the ADC input is above a threshold and if it is, a ADC conversion should be done.
  • 0 in reply to TER
    Prodigy 210 points

    I have read the ADC and COMPB section in the helpviewer and i understand the connection between them.

    But is there a way to use the COMPB for another PIN, than the selected ADC PIN(s)?

    In my application I have to monitor one analog PIN, that doesn´t need a AD conversion and it should need as less current as possible, so the COMPB would be better for the application, than the COMPA, which needs more current.

  • 0 in reply to Philip Scharf
    TI__Guru**** 317180 points
    Since the COMPB input is physically connected with the ADC input and the pin mapping is static I believe you have to use COMPA in this case.