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ADC Behavior Coming out of VLPS (KL25)

Question asked by Chuck Horkin on Aug 26, 2014
Latest reply on Aug 27, 2014 by jeremyzhou

I have been tracing down a bug where we loose communications on our USB BULK_OUT pipe (in from PC host) after several transitions in and out of VLPS and RUN modes.  I finally was able to catch it with a debugger and it seems that the code is getting stuck in a while loop waiting for the ADC COCO bit to be set. 


The code is as follows:

   volatile uint16_t dummyRead = ADC0_RA;

   ADC0_SC1A = ADC_SC1_ADCH(channel) ;     // start conversion

   while(!(ADC0_SC1A & ADC_SC1_COCO_MASK));

   dummyRead = ADC0_RA;

   return dummyRead;


I had looked at the ADC registers and saw nothing suspicious.


So, I looked at the KL25 Reference Manual and I found a subsection under ADC that states the ADC is reset upon exit from Low Power Stop.


So, I made a new build that reinitialized the ADC after coming out of VLPS, but before reenabling interrupts.


I ran with this code, but it seems like it is still hanging.  Has anyone had any similar problems before?