We all need to hack around with hardware from time to time. A highly useful way
to gain access is the RS-232 serial connector to a terminal interface, where
console output is dumped, and command access is often available.
This is available on virtually all digital circuit boards as an
optional pin header and virtually always at a 3V3 level. Why not agree on a simple
way to unleash these with a carefully specified jack plug, and be compatible?