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ADC wiring on stm32f303re Nucleo board

Question asked by David Pekin on Jan 3, 2018
Latest reply on Jan 4, 2018 by David Pekin

Hello,

 

I have a simple application where I need to sample a single ADC line periodically.  I can use polling rather than DMA and interrupts since the timing requirements are very slow.  

 

Anyway, I've taken an ADC sample and started to run it but I'm not getting what I would expect for the 12 bit single ended ADC reading. When the analog input line is floating, I get a value around 1700.  If I tie the analog input to ground I get a value around 1700.  If I tie the analog input to 3.3V  I get a value of around 1700.  If I tie the analog input to 5V I get a value of 4095, the top rail.  

 

Is there some external reference wiring needed  on the Nucleo board to make the ADC work?

 

Thanks,

 

Dave

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