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STM32F3 Discovery - ADC Offset

Question asked by fox.matthew on Jul 10, 2013
Latest reply on Jul 13, 2013 by fox.matthew
I'm working on getting the ADC fully integrated with the rest of my code.  When I'm testing out my ADC, however, I keep getting an output of about 300-400 from ADC1->DR when I'm inputting a voltage of 0 to the pin.  I have six pins configured for the ADC, and all of them exhibit this behavior.  Furthermore, if I put in a voltage of 2.9 or higher, I am maxed out at 4095.  Does anyone know why the values between 2.9 and 3.3 don't register a difference in output?

One of my speculated reasons for this behavior is that I have stopped waiting for the hardware to tell me that it is done with calibration (for reasons I stated in another thread recently).  I am wondering if this could be a product of incomplete calibration.  I'm not sure what really happens during ADC calibration, and if someone knows, I'd love to have a quick description.

One other question that I have is whether this offset would be generalized across devices.  I'm currently working with just one discovery board, but I'm planning on putting this chip on a new board, and i'd like to know if I can expect this sort of offset, or if this is a product of this just chip.  

Thanks so much for any help you can provide!  I really appreciate it