add an output device to a microcontroller board you've designed and program it to do something
For my modification, I chose to add a button (to the RESET) and a servo motor to an ADC pin on the ATTiny44 chip with my unipolar stepper motor:
I began by going through the PCB design process - laying out components on Eagle, routing the board, milling it out from the modela, and soldering on the components.
However, there is something wrong with my power supply... When I plugged in my 9V battery, the board started smoking at first but over time things seemed to be okay. I would be able to hear a sound of the motor ticking back and forth. When I touched it I could feel it vibrating slightly.
Tools:
Datasheets > Eagle > FabModule > modela > AVRDUDE