/diy/ - Do It Yourself

>>1486745
5V tolerance refers to signals, not power. your ESP8266 module may have a regulator on it to feed the SoC the 3.3V it wants for power, but still be damaged by 5V on logic inputs
neither Espressif SoC is rated as 5V tolerant and neither will accept more than 3.6V on its +ve pwoer inputs
anyway why are you still using 5V logic in 2018

>>1486950
can't tell you without seeing how they're connected, i.e. the back side of the board
maybe the designer put them there to protect against ESD, who knows

>>1486756
if you can't read the OP and see the book recs there, what makes anyone think you'll read a whole book