The PlayStep Mini is a tiny device that allows a parent to limit screen time from any HDMI device based on “charging up” energy using an exercise stepper.
The accompanying codedojo article
License for hardware and software: GPL 3.0
EasyEDA pcb project to clone/edit
Atmega328 setup:
The .hex and .ino source for the Atmega328 are in the Arduino sub-folder.
Should be run at 8mhz internal clock. (the PCB supports adding a crystal as well, but you don't need that to use the optional ISCP interface to write to the chip. (well, unless you mess up the clock fuses, in which case you might. Or remove the chip and use a TL866 II+ to fix it)
See this screenshot for fuse settings
The .ino source file can be compiled with the Arduino IDE, make sure you set it at 8mhz.
Credits:
PlayStepMini code/design: Seth A. Robinson
Some peizo beeper effects are taken or modified from the Volume Library Demo Sketch (c) 2016 Connor Nishijima which is released under the GPLv3 license. https://github.com/connornishijima/arduino-volume