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TM4C1294NCPDT: ADC Skew Sampling

Hiroyasu Tazawa1
Guru 12350 points
Part Number: TM4C1294NCPDT


Hi, Everyone

I have a qestion about ADC Skewed Sampling of TM4C129x.

Skewed Sampling is descrived in Figure 15-5. Skewed Sampling of Datasheet.
Is it possible to use Timer Trigger ?

and Do you have any sample code ?
If yes, Can you send me ?

Best Regards
Hiroyasu

  • 0
    TI__Guru**** 191906 points
    Hi,
    I think it is possible. You will need to configure the PHASE of one of the ADCs. If you want to create a 180 degree phase lag you will configure the PHASE of one ADC to be (TSHn +12)/2. Note the time from ADC trigger to sample is increased and could make the response time longer than anticipated. The added latency could have ramifications in the system design. Designers should carefully consider the impact of this delay. Currently there is no sample code for skewed sampling to double the sampling rate. Please also refer to the API ADCPhaseDelaySet().
  • 0 in reply to Charles Tsai
    Guru 12350 points
    Hi, Charles

    Thank you for your reply.

    Why do you think respnse time is longer than anticipated?

    Best Regards
    Hiroyasu
  • 0 in reply to Hiroyasu Tazawa1
    Guru 12350 points
    and My customer want to use DMA with ADC.
    Is it possible to use together for 1MSPS?

    Best Regards
    Hiroyasu
  • 0 in reply to Hiroyasu Tazawa1
    Guru 117855 points

    Firm/I have done very similarly - but w/another's faster MCU.

    To boost your learning/confidence building - you may consider the design of an appropriate frequency, linear, voltage ramp. That enabled our group to accurately determine the (near) exact point in time (signal aperture) of each ADC channel.

    Note too that your entire, Analog signal chain will impact this measurement - and that chain may distort your signal's fidelity...

  • 0 in reply to Hiroyasu Tazawa1
    TI__Guru**** 191906 points
    Hi Hiroyasu,
    The reason is that you will adding PHASE delay and this delay add latency from the time the trigger is received to the time the input is sampled.
  • 0 in reply to Charles Tsai
    Guru 12350 points

    cb1_mobile, Charles

    Thank you for your reply.
    I got it.

    Best Regards
    Hiroyasu

  • 0 in reply to Hiroyasu Tazawa1
    Guru 117855 points

    Thank you - again to further clarify - driving that ADC channel w/a (properly) linear ramping (in range) voltage will aid your determination of the "near exact" moment of the ADC's capture of the (varying) input signals.   (especially the delay between successive, phased conversions)    

    Such "extra care/effort" adds much to your (real) understanding of the MCU's "real world" capability...