ESP8266 Boot Config GPIO and Onboard LED

Last modified by Victor Zhang on 15:13, 17/04/2020
  • Ref: http://www.forward.com.au/pfod/ESP8266/GPIOpins/index.html
  • Summary:
    • GPIO0/GPIO2/GPIO15 pins are used to determine in which mode ESP8266 will boot, so avoid using them as persistant pulling Input source.
      • A button with normally open to Ground with internal pullup is OK
      • A button with normally closed to VDD/GND is likely NOT OK (Only OK when it fits the mode for booting, however will possibly make reprogramming impossible)
      • Sensor module which will have a High/Low to the chip is NOT OK (sometime will make it try to go into program mode)
    • In the generic NodeMCU, the PIN identifiers are: D3,D4 and D8
    • Use them as output is the best practise
    • GPIO2/GPIO16 also connected with Drain mode LED( Low level light up), identifiers are D4 and D0
    • Ref: https://lowvoltage.github.io/2017/07/09/Onboard-LEDs-NodeMCU-Got-Two
      LED Pos
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Created by Victor Zhang on 13:12, 17/04/2020