After two years, I released an update of the Sonoff S20 firmware. Since 2018, I have owned 5 Sonoff S20 to control my home servers and 3D printers at home.

The new improvement are the following:

• Turn on the green LED and turn off the red LED when the switch is open.
• Turn off the green LED and turn on the red LED when the switch is closed.
• Enable button switch as a physical switch button.

You can download my new firmware with an instruction in my bREST example repository. See link here.

Happy Hacking!