I got my prototype circuit boards and have done a little testing. I have trim pots to calibrate the circuit (no software) to set the gauge needle on the full line with 0% duty cycle and the empty line with 100%. The gauge shows 1/4 full with 46.1% duty, 1/2 full with 25.4% and 3/4 full with 12.3%. I was hoping the half full would be 50% so the duty cycle would be a linear function.

Now I'm going to try my second fuel gauge and see if those values hold pretty close.

After I finish the gauge driver testing, I will start testing the sender tests. Then I have to start writing software to link the two (sender and driver). I will probably just have some tables for the link since I'm using a basic micro without complex math functions.

FYI: The gauge has a lot of filtering itself. It takes about 30 seconds to move the needle close to match the duty cycle. The readings near full seem to have more filtering (takes longer). It still will take software filtering to prevent "gas slosh" from moving the needle. It would take a longer filter to prevent a 5 or 10 minuet hill climb or hill drop moving the needle. Not sure how much filtering will be best for most users.