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56F8013 demo board: Analog To Digital

Question asked by Brett Clark on Oct 31, 2006
Latest reply on Mar 27, 2007 by Giacomo Petrini



I have several questions concerning the 56F8013 demo board and more specifically the chip in general. We are attempting to do analog to digital conversions. I put together a variable voltage 'analog' source using a potentiometer and the power supplied by the demo board. I fed ~1 volt into the appropriate pin and attempted to program the ADC bean in CodeWarrior. I will venture to tell you right up front that I am a computer programmer by trade and am not a great electrical engineer. I setup the system to use an 'internal' voltage reference which, I assume, means comparing input voltage to the power supplied to the chip. With all the testing I've done so far, I can't figure out how to get a value other than zero after the ADC event fires. Apparently something is not working right. So, must I have a voltage reference in 'hardware' (i.e., wiring up a pin) or can it be set in software (or need it be set at all)? If so, where do I set it? Any suggestions concerning this would be great. Also, I'm hoping to get 3 channel's out of the ADC. I want to sample 3 independent sources (all with the same voltage ranges!). Is this possible? Or will we not have enough pins (presuming that the voltage reference would have to be set in hardware)? Any information about the process in general would be very welcome. If there are any things that you think I should be aware of, please make them known (this is the first time I've worked directly with an ADC). I have hopes of sampling all 3 channels about 100,000 times per second. With my calculations, I'm not entirely sure that I would have enough time to save it off to external RAM. Is this true or do you think I can do it? If you think that 100,000 times per second sounds too high, what is the maximum speed that I could sample at, do you think?



Message Edited by Alban on 2006-10-31 10:01 PM