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How does the ADC calibration work?

Stian Soevik
Expert 1295 points

Hi, this question applies to both 2809 and 28335, so please point out any differences.

  1. There is an internal ADC calibration routine in boot rom. This exists in 28335, but not in 2809, correct?
  2. Will the calibration routine in boot rom actually perform calibration, as fig. 1-12 in SPRU812A shows, on every startup, or does it transfer pre-programmed values from factory?
  3. The routine converts ADCLO. Is there a dedicated ADCLO input channel, or does one of the 16 ADC channels have to be connected to ADCLO in order to perform calibration?
  4. Is it recommended to perform the calibration routine on each boot, or once in production and store the values?
Edit: I found some answers in the FAQ. Maybe these should be in the application note and/or user manual?
  • 0
    Guru 192875 points

    Hi,

    Will the calibration routine in boot rom actually perform calibration, as fig. 1-12 in SPRU812A shows, on every startup, or does it transfer pre-programmed values from factory?

    -> The boot ROM automatically calls the ADC_cal() routine to initialize the ADCREFSEL and ADCOFFTRIM registers with device specific calibration data. (Every time the controller is booted/startup)
    Is it recommended to perform the calibration routine on each boot, or once in production and store the values?
    ->Generally, we follow ADC calibration every startup.
    Regards,
    Gautam
  • 0 in reply to Gautam Iyer
    Expert 1295 points

    Thank you for your answer. To clarify, i wanted to confirm that the ADC_cal does not actually perform a calibration, but just transfers constant values. My understanding is that this is what happens.

  • 0 in reply to Stian Soevik
    Guru 192875 points

    To clarify, i wanted to confirm that the ADC_cal does not actually perform a calibration, but just transfers constant values. My understanding is that this is what happens.

    Here,

    constant value = device specific calib. data 

    Regards,

    Gautam