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 on the I²C LCD backpack. to fix it, I soldered two coated wires through the pin holes of the backpack and crossed soldered them
- the USB D+ resistor is on the 3.3V power rails, preventing to disconnecting from USB when powering down. to fix it, connect to the nearby VDISPLAY power rail instead
