I have run into a bit of trouble with a sewable electronics project. I am trying to power a SparkFun 7-Segment Serial Display from one of the analog ports of a ATmega328 board. I realize this is unconventional, but I designed the circuit to not require any crossed connections to make the sewing a bit easier, and that was the only way to do it. The display wouldn't light up, and after some debugging with a multi-meter it turned out that the analog pin I was using (A3) was only at 1.3V despite a digitalWrite command. I tested the same command on one of the other analog pins (A0) and it produced 5V as expeced. When I bridge the VCC pin and A3, everything works fine. When I set A0 to 5V , and bridge it with A3, the output voltage drops to 1.8V relative to GND.
The really weird thing is that just running the example code from the sparkfun website without any modifications still somehow results in a \~1.2V reading from A3 to GND. I have no clue what is going on here. Usually I would disconnect the display from A3 and keep testing, but I am trying to avoid it. Troubleshooting is difficult as I had to clip the excess tails to prevent short circuits making me extremely reluctant to disconnect anything until I have figured out what the problem is, as the thread is very hard to work with, and it took the project on the order of 60 man-hours to get where it is. I was hoping someone here might know what is going on, or point me in the right direction.