Hello all. I have a very simple setup that was working great untill I changed the voltage referance settings on my ATMEGA48.
The goal of the system is to read a small voltage on the ADC and send the raw reading to the UART. It is a very simple circuit.
When I had the referance voltage set to AVcc the systme worked great, but when I changed the referance voltage to use the AREF pin, the ADC always converts to 1023. When I measure the voltage at ADC PIN0, I get 91 mV. When I measure the voltage at AREF I get 183 mV. I am using a high impedance multimeter (Fluke 16). Vcc is 3.28 Volts.
The AREF voltage is supplied by a voltage divider that uses 20 OHM and 340 OHM resistors.
Any help is greatly appreciated.