Alright, I have an incredibly frustrating problem that has me stumped. I’ve been using Uno R3 boards and Wiznet WS5100 shields for communications on my flight simulator instruments, and they have worked great (goodbye USB!!!). My usual method is to work out how to drive the instrument straight from just the Uno board and virtual serial (USB) for communications/debugging at first.
I got a gauge working PERFECTLY tonight with the debug/development arrangement.This particular instrument relies on one analog input for a potentiometer. I was using A0. This input is pulled down by a 22k resistor to ground. After thoroughly testing the gauge itself, I then stuck a Wiznet on top of the Uno. However, before touching my code, I went ahead and fired up the gauge again just to make sure all was well. Well, all was not well. My analog input is now reading too high… It’s functioning like something is biasing the pot. I tried switching to A1 just to see if this Wiznet was mysteriously using A0 for something, but results were exactly the same. I also tried adding in the ethernet code to initialize the Wiznet and get it running, thinking perhaps having it in a “zombie” state did something odd. No change. I also tried another Wiznet to make sure I didn’t have a dud.
To clarify, zero on the analog input is still in the same position on the potentiometer, but 1023 comes up sooner. The offset doesn’t seem to be linear throughout pot travel, otherwise I could put in an arbitrary offset or scaling factor to my analog reading just to “make it work”.