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ADC1 and ADC2

enrico terraneo
Intellectual 695 points


Dear All,

I'm using TMS570LS1227 MCU.

Are the ADC1 and ADC2 modules different?

My four analog inputs are connected to both ADC modules. ADCs are set to 12 bit. The start of conversion is execute by external hardware trigger.

I have the following problem: there is a difference about 5 point converter between the ADC modules.

Note: I tried to calibrate both ADCs, but the result doesn't change.

 

Thanks and best regards.

  • 0
    TI__Mastermind 22375 points

    Enrico,

    Our ADC expert will take care of your question.

    With the Holidays this week, our response time may be a little longer than usual.

  • 0
    TI__Mastermind 49120 points

    Hello Enrico,

    The ADC1 and ADC2 modules are identical. They have 16 shared input channels. Please confirm that both the modules are configured in exactly the same manner in terms of timings (sample time, ADCLK frequency) and the conversion trigger event. That is, the same external hardware trigger starts conversion of the same channel on both the ADC modules.

    You do not need to calibrate the ADCs as long as you do not need accuracy better than that specified in the part's datasheet.

    Regards,

    Sunil

  • 0 in reply to Sunil Oak
    Intellectual 695 points

    Hello Sunil,

    I confirm that both the ADC modules are configured in exactly the same manner (sample time, ADCLK frequency) and the conversion trigger event.

    I used:

    • the same external hardware trigger to start the conversion on both ADC modules.
    • the conversion Group 1

    The only difference is that the ADC1 modules has other four analog inputs, but they are configured in conversion Group 2 and, for this Group, the start of conversion is executed by software trigger, it is perfomed at different time than Group 2.conversion.

     

    Regards

  • 0 in reply to enrico terraneo
    TI__Mastermind 49120 points

    Hello Enrico,

    Can you confirm that you see this 5 count offset even when you turn off the group2 on ADC1? My understanding is that the group2 conversions are delaying the trigger of group1 conversions so that the two ADC modules are not exactly starting to sample the inputs at exactly the same time.

    Note that triggering another group's conversion while a conversion is ongoing effectively creates a "pending conversion" which then takes place once it gets its turn as per the arbitration scheme.

    Regards, Sunil

  • 0 in reply to Sunil Oak
    Intellectual 695 points
    Hello Sunil, Yes, I confirm that I see 5 count offset even when I turn off the Group 2 on ADC1. Now, I have tried to configure only group 1 on ADC1 and only Group 1 on ADC2 and there are always 5 count offset. Thanks