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AWR1642: How to understand the GPADC sampling counter and settling Time?

Wesley He
Expert 6205 points
Part Number: AWR1642

Hello team,

In AWR1642 we can config the GPADC sampleCnt  and settlingTime  shown below.

.numOfSamples[0].sampleCnt = 20,
.numOfSamples[0].settlingTime = 3,

The settling time is 0.8*3 = 2.4us. If enable all 6 GPADC channel. Is that means we need 2.4*6=14.4us to finish one round sample?

And how to understand the sampleCnt? if i change 20 to 255, will it increase the GPADC data buffer size? 

My understanding is it will record the avg, max, min value of the setting sample number. Is my understanding correctly?

Thanks.

Wesley

  • 0
    TI__Guru*** 149044 points

    Hi,

    The hw team will review this question and get back to you

    thank you
    Cesar

  • 0
    TI__Guru 58035 points

    Hello Wesley,

    The settling time is the time the SW will wait before starting the measurements, this is mostly to allow for voltage settling while switching from one channel to the other.

    The number of sample is the number of ADC samples the SW will take and use them to compute the average, min, max. The total time required will be total settling time + the time taken to take the N samples.

     Regards,
    Vivek

  • 0 in reply to Vivek Dham
    TI__Expert 6205 points

    Hi Vivek,

    To better understand how the GPADC work in 1642. I had draw a simple figure to better explain my confuse. i had listed 3 kinds of ADC work mode.  

    Can you please point out which mode is used in AWR1642? The 2.4us shown below is the sample settle time. And suppose each time, ADC is working in 625Ksps mode.

    If i have lost anythng, please point it out. Thanks.

    Regards,

    Wesley

  • 0 in reply to Wesley He
    TI__Guru 58035 points

    Hello Wesley,

    Its the second figure that you have depicted. ie one sample is taken from all the enabled GPADC channels, then the next sample from all the enabled GPADC channels etc.

    Please note that only the enabled GPADC channels will be cycled through, so if you use only 2 GPADC channels then only those 2 GPADCs will be sampled.

    Regards,

    Vivek

  • 0 in reply to Vivek Dham
    TI__Expert 6205 points

    Hi Vivek,

    One more question, as you describe, "one sample is taken from all the enabled GPADC channels, then the next sample from all the enabled GPADC channels etc."

    But in my second figure, 20 samples is taken from one GPADC channel, then move to next channel.

    Is it you means third figure i shown?

    Thanks,

    Wesley

  • 0 in reply to Wesley He
    TI__Guru 58035 points

    Hello Wesley,

    Sorry , I missed the top row. It is the 3rd figure I was referring to.

    Regards,

    Vivek