I found some tips on GitHub and Stackoverflow, however none of them worked for me.
Using this guide (https://github.com/yaourdt/mgos-to-tasmota) I was able to successfully flash OTA; first Tasmota, then Tasmota Minimal and then again the recovery firmware (1.5.10).
Using this, I was able to do the calibration.
Thank you very much your crucial hint! 
Ok so I've now wired my Shelly like this:
When I plug in the USB, I see no difference in having the yellow wire (GPIO0) grounded or not (e.g. flashing LED on the Shelly or similar).
I also tried switching RXD and TXD (RXD -> RXD, TXD -> TXD vs. RXD -> TXD, TXD -> RXD).
No Matter what I do, the Shelly does not seem to connect:
Is it broken?
Hello everyone,
I have a 3T35-10B roller shutter (https://www.3t-motors.de/3T-Motors-Roll…-10Nm-SW40.html) that I want to control with my Shelly 2.5.
I already have four Shellys in my house that I was able to successfully calibrate.
With this new one however, the calibration simply stops nearly at the end and my app/browser tells me it failed.
Here is what I have tried so far:
* set the Shelly to roller shutter mode
* set the working time to 120 seconds
* tried the app and different browsers
* reset the device
The roller shutter moves down entirely, moves up entirely, then moves to ~20% open and stops for a while, then
* either moves to ~50% open and stops
or
* just stops
and tells me the calibration failed.
In the debug.log.txt however, I cannot see any issue!?
Firmware is 20210909-144331/v1.11.4-DNSfix-ge6b2f6d.
What can I do??? 
As I've learned today, diyHue supports the Shelly1 out of the box.
So there is no need to develop my own firmware.
One big advantage over using a custom firmware is that the Shelly1 stays controllable and configurable via Shelly app.
More details here: https://github.com/diyhue/diyHue/pull/362
Taking alook at the following schematic
https://shelly.cloud/wp-content/upl…lly1_pinout.jpg
it should be as simple as setting GPIO4 to HIGH, shouldn't it?
I will try this out tomorrow. If anyone can confirm this before I burn down my house I would really appreciate it 
But shouldn't this be documented somewhere?
Tasmota somehow manages to toggle the relais, so it should technically also be possible with a custom firmware, shouldn't it?
Obviously you didn't get it.
I am free to tell my firmware whatever I want, sure.
But how does my custom firmware tell the hardware to toggle the relay?
So what function should I use to toggle the relay via my own code?
To ask the question in a different way: I have an idea how to write my own firmware that is compatible with diyHue. What I don't know is how I can programmatically switch the relay on and off.
In case I write my own firmware, the API commands listed in https://shelly-api-docs.shelly.cloud/#shelly1-shelly1pm will not work anymore, right?
Hello guys,
I just received my first Shelly 1 and wondered if I have decided to quickly since I cannot find any answer to my question.
I know that the Shelly is based on WiFi and is not able to speak ZigBee ootb (or even at all).
However, I have several NodeMCUs (based on ESP8266) in my house that I control via diyHue. So, technically it should be possible to enable a WiFi device to speak ZigBee (or at least make the Hue Android app think that those are ZigBee devices since the diyHue fake bridge running on my NAS tells the app they are).
How is this possible with the Shelly 1? Initially, I was just scanning the Tasmota documentation for 5 minutes before going to bed and ordered a Shelly 1 since I found a section for "ZigBee". But reading it in detail now, I am completely clueless on how to make the Shelly 1 function like a ZigBee switch.
Does anyone have an idea?
