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Updated Expanding 4CH (markdown)

Gennaro Tortone 2018-01-26 22:58:29 +01:00
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Expanding-4CH.md

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Opening my Sonoff 4CH (https://www.itead.cc/sonoff-4ch.html) I realized that on PCB there is a predisposition for 2.5 mm jack plug (also confirmed by schematic on Itead wiki: https://www.itead.cc/wiki/File:Sonoff_4CH.SCHMATIC.pdf) Opening my Sonoff 4CH (https://www.itead.cc/sonoff-4ch.html) I realized that on PCB there is a predisposition for 2.5 mm jack (also confirmed by schematic on Itead wiki: https://www.itead.cc/wiki/File:Sonoff_4CH.SCHMATIC.pdf).
I ordered on Aliexpress some 2.5 mm jacks and when I received it after some work...
![](https://github.com/gtortone/Sonoff-Tasmota/blob/development/_temp_imgs/sf4ch-jack.jpg)
The schematic reports that 2.5 mm jack is configured as following (jack on right side, ESP8255 on the left side:
![](https://github.com/gtortone/Sonoff-Tasmota/blob/development/_temp_imgs/sf4ch-schematic.png)
3.3V and GND are very welcome for sensors expansions but GPIO7 and GPIO8 are not usable because they are used internally by ESP8255 for flash memory connection (sigh!)
R35 and R36 resistors are not soldered on Sonoff 4CH PCB and it is possible to use them to "manually route" the jack contact on another ESP2855 pin (!). I selected R35 pad due to my DS18B20 sensors that provide signal line on that jack contact TEM1. For ESP8255 pin I prefer IO2 that is already available on header programming pins...
Then the route to do is: TEM1 -> R35 pad -> IO2: