version 1 (2019-11-17):
- first finished schematic and layout
- prototype board ordered
- the button footprint is wrong. to fix it, cut the top left lead to break the connection to ground, and solder on of the bottom lead to the surrounding ground.
- in the schematic I switched SDA and SCL to the I²C LCD backpack. to fix it, I soldered two coated wires through the pin holes of the backpack and crossed soldered them.
