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K20 (ADC or DMA issue) ADC results are half of the correct value

Question asked by nicholasf on May 7, 2014
Latest reply on May 9, 2014 by EARL GOODRICH

I am using the ADC on a K20F120, and getting results that are exactly half what they should be (according to an oscilloscope which I am measuring the input with).  My configuration is as follows:


core clock = 120 MHz
bus clock = 60 MHz

ADC clock = 7.5 MHz
ADC mode = 16 bit differential

ADC trigger = software triggered, free running


ADC triggers DMA transfers on conversion complete


ADC is calibrated before being used

ADC is running at correct speed

No PGA configured

ADC range is 0V-3V (approximately the same as Vdd)


I can post the configuration if that would help (I am not using processor expert), but I am wondering if anyone has encountered this issue before.  It looks as if the results are being right-shifted.  The problem could be something with the ADC or DMA.


Any input would be greatly appreciated. Thanks for reading my post!