Shutter/Blinder with Tasmota on Sonoff 4CH Pro and Somfy IO Sender


I have a question that I cannot solve on my own: I have a somfy awning that uses a proprietary protocol (IO) and thus cannot be easily integrated into my Home Assistant instance.

However, I have found a bypass using a Somfy in-wall transmitter that can communicate with the awning motor: The sender module has two buttons (S1 and S2), one for up, one for down.

I have hooked this up to a Sonoff 4CH Pro flashed with tasmota (the sender is potential free), S1 is hooked to relay 1 and S2 to relay 2. Going up and going down works well .

However, I have two problems here:

  1. to stop the awning at a certain point, both buttons need to be pressed. I do not know how I can implement this via the shutter functionality of Tasmota. Is there an option to have a ‘virtual’ third button by combining the two relays?

2( obviously, there is no load on the sender module and thus I do not know how I would calibrate the shutter and get back the position of the awning.

Has anyone implemented something similar and can give me a hint?