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MPC5554  Strange ADC Sampling Problem

Question asked by kaixiong lv on May 27, 2018
Latest reply on May 30, 2018 by David Tosenovjan

hello,I have a strange problem using MPC5554 ADC module.

I want to use ADC to sample 2.5V voltage, the accurate number should be 8192 in decimal. firstly, I sample the channel 42, the result is Result[0]= 8221,   then I sample 2.5V voltage generated by the singnal generator,the result is U0=8506; then I put the same code into for loop, as the picture above shows, the result is U1=9800.

 

U0 is a little larger than  Result[0], maybe I can calibrate it and it will be OK.    But why U0 is different from U1?  the code is the same, why the result is different?   the only diffrence is U1 is in the loop and U0 is out of the loop.

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