I am trying to use an MCP4725 to output a voltage (0-2V) I can get it working fine when the arduino is connected to a PC via USB. When I try the arduino as a standalone, the DAC is not outputting the correct value. I have the SCL and SDA connected to the SCL/SDA ports and ground connected to ground. I have tried the VCC connected to the 5V and 3.3. Also tried AREF but no luck when the Aduino is stand alone. Do the pullups need to be cut? Not sure what I am missing
Please post the code, using code tags, and a wiring diagram. We need the details on how you are powering the setup and communicating with the Arduino.
I was able to get it working. My original idea was to have the PORTD as inputs, selector switch position would drive the input of the pins HIGH and then read the register. I went to using the internal pullups and driving the pin low for the switch positions. A different values are sent to the MCP4725 depending on which switch position is selected.