This PIC16F690 based panel lets you control a RaspberryPi with a serial communication protocol like I2C, but uses
a bitbang technique, the panel is the master and the raspbarry is the slave. The system has 2 rotary encoders
and 4 buttons, it takes power from the Raspberry.
This version has a better filter on the encoders, led backlit on knobs and buttons, below some photos with different colors.
For plastic overlay/mounting panels + video click here.