I'm looking for the GPIO's I can use in SonOff Dual ( after flashing my own software ). In SonOff Basic - there are GPIOs to acess LED, Relay, and what is most needed for me - GPIO14 for external input as shown here

Since I need 2 Relays solution, I need 2 external inputs. I'll be happy to get some assistance in finding those "free GPIOs"


Sonoff has only 2 GPIO pins, button 1 and button 2. Other 2 GPIO pins are used for two relay outputs. Refer here



I hope this helped.

  • GREAT !!! - I did not find anywhere such table. can you tell that it is actually ESP8266 ? since in another answer it says it is ESP8285 – Guy . D Sep 5 '18 at 17:21

According to github,

Sonoff Dual R2 is the replacement for Sonoff Dual. Compared to the Dual the main differences/improvements for the Dual R2 are:

  • As the second microcontroller has been removed both relays are now controlled directly by an ESP8285

From this, I deduce that the 'free' GPIOs may not exist in the same way.


All the Sonoff devices schematics are on the Sonoff web page. Scroll to the bottom for a PDF of the schematic: https://www.itead.cc/wiki/Sonoff_Dual.

This schematic shows that, apart from the relay, button and LED GPIOs, (which you probably should not play with, since they already have functions), the Rx and Tx pins (clearly labelled on your board) are also GPIO pins. You can solder another header on there. I don't know what software "your own" is but firmware like TASMOTA, for example, allows these pins to be reconfigured for whatever function you wish: they can take on the functions of GPIO4 and GPIO14 on other style boards, or even be used as I2C.

I have used these schematics to add 2.5mm jacks to Sonoff Basics. Be sure to check against the version number on your board. There are instructions out there on how to modify a TH, but I think it's a really old board.

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