AnsweredAssumed Answered

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!

Outcomes