I'm using the ADC on the MSP432 evaluation board and I decided to check it's accuracy by connecting my analog inputs straight to a power supply. Originally I was able to read the voltages pretty accurately from my power supply, and then I tried to read it while the power supply was turned off with pull down resistors in place. Instead of it reading close to zero I'm getting about 150mV on each of my inputs. I switched to using batteries to see if the USB was my problem but my readings didn't change much. After switching back and turning the power supply back on the 150mV offset remained. I set up two digital pins as inputs which respond to two different push buttons, powered by the 3.3v output of the MSP432, in order to start polling my ADC pins for voltages. I have one pin acting as a digital output to produce a voltage across series resistors in order to make a resistance measurement. I wrote all my code in Energia primarily using the analogRead function. I noticed that when I would use a DMM to measure the same point as my ADC channel it would typically cause the offset voltage to decrease. On a side note, I have a second board that I believe may be defective. When the same code is uploaded all of my inputs start to output 3v.
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