Posted on May 17, 2011 at 11:51Chip uPSD3354DV-40T6.
I am having am issue with ADC. I am using 3 adc input pins ADC5-7. ADC5 is working perfect I get the result with +/-4 counts. On ADC6/7, my result of off. I am testing with several different resistor measurements on each ADC pin. I can measure the correct voltage on pin ADC6/7, but the ADC result does not match the measured voltage goining into the pin. ie. Using a 10K resistor, ADC5 results in 515 counts, expected 512. ADC6/7 counts are 545, expected 512. Measured voltage on ADC5 is 1.674, Vref is 3.35V. Measured voltage on ADC6/7 is 1.676, Vref is 3.35V. So you can see the voltages are almost the same, but the adc result is very different. I have a 0.1uF cap on the input pin to eliminate noise.
What can be causing this issue? I am using the ADC demo code from the DK3300-ELCD. I changed the conversion use IDLE mode and let the ADC interrupt bring me out. I am using a 14.7456 MHz crystal, so ADCPS is 0x08.
