Electronics reminder snippet: Pull-down an IO pin with a transistor
NPN – eg 2n3904, 10k on base, 1k on collector Use when the IO-pin has to be up by default PNP – eg 2n3906, 1k on collector Use when the IO-pin has to be down by default, eg IO2 on ESP8266 for boot conditions Make some notes about what happens, and some code for an …