Problem reading analog signal from A0!

Using Arduino Installation & Troubleshooting
#1

Hey All -- I have a project working with the Mega, and i've been having an issue getting a reading from the A0 pin. Every time I hook up an analog signal to it, the arduino pulls the signal up about 1.5V; it's as if it is set as an output, or the pull-up resistor is enabled... But the script is configured just to analogRead(A0), and nothing else... And when I switch it to another analog pin, it works perfectly fine. Any ideas? Is this just a malfunction/problem with my board, or does the A0 pin have some other property that i'm not aware of that is causing this?

Thanks! -Nick

#2

If it only occurs with A0, that sounds like input on the MUX has been damaged.

What happens when the pin is used as a digital input?

#3

I tested the A0 pin as a digital output today, and indeed it did not work. (I wrote a script to toggle HIGH/LOW on the pin, and it stayed hight the entire time...) So the ADC is fried on that channel? Thanks! -Nick

#4

There is only one ADC in the ATmega328. Each of the inputs are connected through a MUX.

If analog and digital don't work, the pin is dead.

#5