Gas gauge calibration unit

It was a rainy day here, so I found time to build the prototype. It varies some in build due to using parts at hand. I used a few surface mount parts for resistors and capacitors. Component values are not very critical in design. The most critical component is the resistor that sets the sender current. The important part is that the sender output voltage stays within the ADC span of 2.56V provided by the micro controller, there is plenty of flexibility there. Errors are calibrated out relying on the 10 bit ADC (about 0.1% resolution), and 8-bit PWM ( 0.5%).

I have started software. I have it figured out. It a matter of writing and testing the code. I will do it in a few steps. First I will get the ADC and PWM going. Next write the function that translates sender values to PWM. Followed by the calibration routine, that interprets button selections, and stores calibration values in eeprom.