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ADC accuracy on first read

Question asked by Guillaume Audirac Employee on Feb 4, 2019
Latest reply on Feb 10, 2019 by jeremyzhou

Using i.MXRT1062, the first ADC value is slightly lower than the expectation.

Settings:

  • Software Triggering
  • 12 bits ADC resolution

The starting sequence (using fsl_adc):

  1. ADC_Init()
  2. ADC_EnableHardwareTrigger()
  3. ADC_DoAutoCalibration()
  4. In loop, at key press:
    1. ADC_SetChannelConfig()
    2. Wait for ADC_GetChannelStatusFlags
    3. ADC_GetChannelConversionValue() at key press

Outputs:

  • First value read: ~3200
  • Following value read: ~3400-3450

Do you have any idea why the first value is not accurate ?

Thanks.

(sample code attached)

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