Feature: Audio Support

[AzonInc]

It would be a nice addition to add audio support to the board and firmware as well.
If you have any knowledge about audio processing or ideas how to send audio on the bus, feel free to share your ideas here.

I've been able to enable and disable the audio mode already but now we need to process the data somehow as a first step.

Streaming an audio file via Homeassistant to the bus would be nice as well.
Or maybe even live audio streaming.

[BiasF]

I tried ring intercom last year, it worked but the audio quality was very bad with a high frequent beep in the background.
Didn't feel comfortable with the cloud connection and sent the device back, but it shows that its possible to build that feature.

[artifactdev]

Might it be possible to "debug" what the ring intercom does, when enabling audio and reverse engineer it? Especially as it is available pretty cheap right now. But as I have it here already and will get a doorman soon, I might be able to support on this.

[AzonInc]

Mhh I'm just not sure how to debug it.
I will have an oscilloscope in the next days, sooo maybe I'll find out something new (after figuring out how to use that oscilloscope haha).

Let me know when u find out anything new :)

[colinmarc]

It seems like it's possible to compile libopus for the esp32 (see for example https://github.com/XasWorks/esp-libopus). One could feed it from an ADC, maybe one of these:

https://github.com/pschatzmann/arduino-audio-tools/wiki/External-ADC

[AzonInc]

The audio stream is somewhat modulated on the DC but I'm not sure, I couldn't measure any AC.
It's ~22V DC base and ~1-2V audio on top

We just need a way to extract the data.

[colinmarc]

Disclaimer: I have no idea what I'm talking about

I think what's need is an op-amp to measure the difference between the audio signal and the 22v baseline, and then amplify it to the range that the ADC wants (usually 5v or so?). See "difference amplifier" here https://forum.arduino.cc/t/using-operational-amplifiers-in-your-arduino-project/692648/4