SONOFF S20 : how to connect a reed switch

[Gilles]

Hello,
I would like to use a SONOFF S20 along with a reed switch to check if the window is opened or closed. Then I will add rules to send a mail if the window is open for more than 10 minutes.

I have read some examples in the forum where LisaM said that using the gpio 1,3 ,13 and 15 is not good, because they are used at boot time, so should not be used. (viewtopic.php?t=3263).

Somewhere else, I have noted that I could use the GPIO 14.
I have no idea how to know where to locate these GPIOs.
I have attached a pix of my SONOFF S20.
I have 2 questions:
1) Is it possible to connect a reed switch to the SONOFF S20?
2) Does someone know where to connect the reed switch to the SONOFF S20 ?

IMG_20190530_181853.jpg (3.13 MiB) Viewed 8958 times

The SONOFF S20 runs Espeasy:
Build: 20000 - Mega
GIT version: v2.0-20180126

Thanks
Gilles

[grovkillen]

If you turn off the serial you may use the RX or TX as GPIO.

[Gilles]

Thanks
I assume that :
GPIO 1 if I use the TX
or
GPIO 3 if I use the RX.

For the record, to disable the serial port , go to Tools, Advanced, and untick the "Enable Serial port:" in the "Serial Settings" section.

[grovkillen]

Yes correctly.