https://www.torretje.nl/files/GU20X8-301.pdf
https://github.com/cawapy/GU20X8Lib/blob/master/GU20X8Lib.ino
https://git.agiri.ninja/natalie/badapple_gu20x8/-/blob/master/badapple/badapple.ino
https://github.com/cawapy/GU20X8/blob/master/gu20x8.md
