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MSP430FR6047: Handling Asymmetric ADC Capture

Eric Nutsch
Prodigy 62 points
Part Number: MSP430FR6047

Tool/software:

Is there a method in the software to offset the ADC capture? The waveform looks pretty decent other than the offset.

I have not nailed down what is causing this offset, but different PCB/transducers combinations have more or less positive or negative offset. I suppose there is variance in each and some combinations cancel out. Any thoughts on what might be causing this?

Thanks!

  • 0
    TI__Genius 12152 points

    There are offset that from hardware.

    If your USS PGA gain is set too high, this will cause the ADC result to offset too high.

    For software method, check the average offset, then subtract this offset from the result

  • 0 in reply to Helic Chi
    Prodigy 62 points

    I have the gain at 16.3 db, which is high and does make the offset larger relative to the signal, but that is what I need for this transducer. It seems to be consistent for a transducer/PCB pair; would there be any way to shift this data programmatically with a constant? For example +150 for the data shown above. Thanks!

  • 0 in reply to Eric Nutsch
    TI__Genius 12152 points

    Since this is normal, please try the method I provide to you:

    Helic Chi said:
    For software method, check the average offset, then subtract this offset from the result

    For a group data, add them together, them calculate the average offset value, subtract this offset from the result

  • 0 in reply to Helic Chi
    Prodigy 62 points

    Okay, mathematically I understand, but I am unsure where to begin in the syntax. I imagine the data is in an array, but I have not located it yet. Do you know of any references or examples of programmatically accessing this data. Even just a variable name would be a big help.  I found calibratedDCOffsetUPS and calibratedDCOffsetDNS in the Ultrasonic Design Center User Guide. These might be the values I want to add the correction coefficient to, but there is very little information on all of the parameters in the user guide. Is there another reference I am missing that details more about these parameters? Thanks!

  • 0 in reply to Eric Nutsch
    TI__Genius 12152 points
    Eric Nutsch said:
    calibratedDCOffsetUPS and calibratedDCOffsetDNS

    Search them in demo code project.

    Yes, it is. UPS is for up stream and DNS is for down steam.

    You can refer to the source code, there are code that add these offset to ADC samples.

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