Trying to connect a siedle BTS 850-02 to homeassistant via Xiao ESP32C3

Hi folks,
I’m researching on this topic for quite a while. Sadly, it took me a long time to stumble over this possible dealbreaker.

I assumed my doorphone was a much simpler HTA-811 but it is a BTS 850 which speaks siedle in home bus. There are a couple promising solutions for other siedle doorphones but I havent seen anything for this one so far.

Does anyone happen to know how to interact with the two bus pins ta and tb? I would like to use my xiao esp32c3 with wifi and BLE to connect it to homeassistant, possible over esphome or if possible even with a sip client. That would be a later step though.

I havent found anything about the siedle in home bus. What protocol they use, if it is encrypted or anything. I guess there would be a solution to manually read from the light that signals a bell ring and send to the door buzzer button if all else fails.

But of course hacking the in home bus would be pretty cool.

I made this git repo to collect information and cooperate with people. You can use gitlab or github logins if you want to participate: Smart_Doorbell/README.md at main - haui/Smart_Doorbell - Forgejo: Beyond coding. We forge.

Any ideas?

That’s funny, I did the same mistake as you.

I thought I had a HTA 711 but it turned out to be a BTS 750 02 which uses the same Siedle in house bus with the ta tb and ERT pins.

I’m also looking for a solution.