From the Tasmota GitHub :
TL;DR
Don’t count on any useful info on this from Shelly
GitHub link here :
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I didn’t get any answer from them as well. I asked the german sales people, and I do believe them in saying they don’t have any info as well.
It is very unfortunate, as I’m not willing to spend another Euro with them right now. And I was hoping for a few dimmers, I do need them. So back to chinese products it is. IMHO this is a dump decision from them, but that’s the way they want to handle it.
I’m gonna give this some time soon. The stm32 is hopefully not read/write protected. If it’s not, then should be possible to flash both mcus.
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My shelly dimmer has only 2MB flash, chip is Winbond 25Q16JVSIQ.
So has anyone managed to sniff the uart while dimming yet?
I’m tempted to jump in on this. I bought 2 shelly dimmers, installed one, and was disappointed to find out they didn’t include the dang switch inputs with mqtt! That is so beta IMHO.
So I am holding off installing the second shelly dimmer in case I need it to capture some data. Great to see some progress RE’ing pinouts, and the flash read. It seems though, that characterizing the uart comms will be the key that holds back development of diy firmwares. The rest GPIO stuff can be sussed out quickly, but we have nothing without being able to talk to the zerocross controller. I’d already be capturing right now, but first I need to sneak purchasing an isolation transformer past the wife, lol.
Yes, it’s all in the tasmota thread. Gihub has hidden alot of useful posts so don’t forget to expand it.
Hay you got the yaml for it…
You should remove this incorrect pinout.
Slightly offtopic but, could anybody tell me if this is dimmer can be operated with a “spring loaded” switch/button that you press down to dim or brighten? And the switch would have to allow pressing from upper or lower edge for increasing/decreasing brightness, correspondingly, right? Any example of suitable switches (not the toggle type)?
You are talking about a dual pole momentary… just fyi, they may do what you need, but they ain’t cheap:
That with a shelly dimmer, and you’re right up there in the price range of legit zwave wall dimmers (IMHO, a zwave dimmer is the better option, especially for now until proper mqtt firmware can be flashed to the shelly dimmer to read switch state… the current web request workaround is IMHO unacceptably laggy… and not sure how this RE project is progressing, but I’d guess it’ll be a while before shelly dimmers can be flashed with like esphome, if ever). Beware most of the cheaper momentary wall switches you find will be single pole, not dual. You need a dual pole unit to do what you want.
Thanks a lot for this great insight. I’ve ordered some shellies so I’ll try how they work. Do you know if they would even support dual pole momentary switch out of the box?
Yes they have 2 inputs for it, and the factory firmware has an option to use them exactly as you described above (up for on and brightening, down for off and dimming). Do be aware though, that the switch will need to be connected to mains (the shelly dimmer inputs must see 120/220 when a switch is pushed to work). Most homes are wired so that isn’t an issue, but just wanted to mention since some devices use resistance instead of voltage for a signal.
The shelly website has nicely illustrated wiring diagrams for all their devices. You should definitely look at those to be sure they will work with your intended application before buying. I for one didn’t realize a shelly I bought for my hallway lights wouldn’t work without significant wiring. It has a 4 way circuit with load on one end, and line on the other end, and shellies need a hot in the same box as the load.
In my case, I could have ‘stolen’ hot from a house fan line (different circuit breaker) that was in the box with the load wire, but I didn’t want half arsed ground loop wiring on my house, let alone shenanigans like using earth for neutral and neutral for hot (shelly even warns against the former practice in their 2.5 manual… regarding i1 and i2 being connected inside). So I had to find another role for that shelly. I bought a set of jasco’s for the hall lights instead (the ge/jasco zwave dimmers work with all 3/4-way home wiring schematics).
Tldr; Before buying a shelly for any 3/4 way light circuit, first open up your j-boxes and determine if you have a box with both line and load wires. If like many 3/4 way circuits you find hot in one box and line in another, shellies won’t work!
Awesome, good to know! We’re actually about to start building a new house so wiring won’t be a problem. Originally I wanted a fully wired solution but few seem to exists unless you move to bus or PLC systems… Anyway, I will test the shellies in my current place and have an electrician install them since I’m clueless about that stuff. I’ll have to look up what you mean by a 4-way circuit and such 
I’m in EU so that sweet GE Z-wave switch probably is not an option…
Just noticed you are mentioning 3/4 way configurations. @porksoda it’s when you can use one switch to turn lights on, and the same or other one to turn lights off. You can often find such in staircases
Anyway, For 3/4 way configurations at least 2 cables must be pulled between switches. And it’s enough if you can afford changing switches to momentary ones. It gives you ability to freely chose a switch’s box where shelly will be mounted. You can find one which all needed cables (Line and neutral). Then connecto two mentioned cables which connects switches to Line and Switch terminal.
Often though, you have the load wires not in the same box where the line and neutral are connected. Here is an example schematic where a shelly dimmer will not work:
To use shelly here, another wire must be added between the 2 switch boxes (14-4-G… of you will). That image came from this site:
http://www.m.electrical101.com/m.3way-switch-wiring-using-nm-cable.html
As you can see there are seceral possible wiring methods. Some will work with shelly, others won’t.
This is the reason why using bi-stable switches is almost no go for most houses.
That’s why I suggest momentary switches instead. Most of regular (bi-stable) switches can be easily/cheap replaced by momentary. Sometimes it’s enough to add proper spring. Or you can replace switching device for momentary of the same design type, leaving old covers/buttons/frames.
I replaced all my switches with momentary ones, regardless it was needed (by 3/4 way wiring) or not. Personally I like them more. They better fit the functionality. They keep consistent position of button. Also allows to use long-press or double-press features.
Here is comparison of wiring, considering there are only 2 wires between switch-boxes existing.
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Well said. That diagram should be useful for folks wiring shellies up. Momentary switches are pricey, but the money saved vs zwave switches (plus being able to program long/double/etc) is worth the change… provided the wife accepts momentaries.