My nephew's Decimilia ADC function does not work. Only reads 5V or 0V. Using the 5V out on the board and a voltage divider to produce 2.5V results in 0V. Reads 5V without divider. How can I tell if ATMega128 ADC function is smoked? Is there a hard reset that can be performed? Or should I just replace the ATMega128 and quit wasting everyone's time!
It is an Atmega168, not 128.
Can you describe exactly how are you reading the values? (hardware and software?)
We used "Graph" from the Arduino Tutorial page...which uses Processing Development Environment. We had been using this program along with the Arduino to digitize and display an ECG signal from a couple of different circuits that we built. The program works for us but his Arduino died (he said he tried to operate a small DC motor by driving an analog signal out and into the motor...he thinks he smoked the ADC). I soldered two identical resistors together to form a voltage divider and used the 5V and GND inputs on the Arduino to complete the circuit. Tapped off between resistors to produce a 2.5V signal into Analog 0. The "Graph" program indicates no value. I am going to try just using the AnalogInput program on the Tutorial page.
Have you tried measuring the voltage at the pin using a multimeter? Not saying you've done anything wrong, but it's worth checking.