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TM4C123GH6PM: ADC Dither Enable

Connor Herron
Prodigy 120 points
Part Number: TM4C123GH6PM

I'm trying to learn a little bit more about Dither mode and how to use it. From what I've read and heard, when enabled the ADC will add white noise which statistically will more accurately represent a value between two step sizes. How all of that works seems to be unconfigurable from what I can see. From what I've read in the datasheet, it looks to only be configurable from accessing the register directly.

Is it configured once for all ADC inputs or each individual module or perhaps each channel?

Any help would be appreciated, thanks!

  • 0
    TI__Guru*** 135355 points
    Hello Connor,

    The Dither enable is done in the ADCCTL register, so as per the TM4C datasheet, "Note that values set in this register apply to all ADC modules" - in order words, it will affect all modules and inputs.

    I don't see an API to configure Dither mode so yes you'd need to use a DRM command to set that bit.
  • 0 in reply to Ralph Jacobi
    Prodigy 120 points
    So I could set the dither bit to one for either module and it would affect the other one too? What's the point of having two bits for each module then?
  • 0 in reply to Connor Herron
    TI__Guru*** 135355 points
    Hello Connor,

    I am not seeing any indicators of there being two bits for Dither mode in the datasheet of the device you have included for this thread, can you clarify if you are looking at a different device datasheet or direct me to which section that you see that? When I searched for Dither in the d/s I only found a register setting for it in ADCCTL that was a single bit.
  • 0 in reply to Ralph Jacobi
    Prodigy 120 points

    I'm referring to the ADC0 and ADC1 base addresses in the top left. I assume that with an offset of 0x038 that means both 0x40038038 and 0x40039038 registers have a dither for their 6th bit.

  • 0 in reply to Connor Herron
    TI__Guru*** 135355 points
    Hello Connor,

    I couldn't find a conclusive note one way or the other that indicates if the Dither mode can be selected for one module or the other. That may be the case because the comment regarding settings being applied across modules was to explain the references, and then it is stated again for the VREF bit, but it is not stated for Dither Enable. So it may well be that Dither Mode can be activated for each ADC module.

    I'm not enough of an analog expert to know how to effectively test this feature out myself, but I will see if another team member can look into that in the near future and confirm if that's the case so the D/S can better clarify this.