Connect by bluetooth or USB serial instead of wifi

[janifr]

Hi,

I have Signal K installed on Raspberry PI 4 and would prefer to connect ESP32 board by bluetooth or wired USB serial connection instead of wifi, because I want to use ADC2 channels, which don't work with wifi enabled.

Is there a way to do it?

TIA, Jani

[mairas]

There's a bit of extra coding to be done, but it should be possible. In the WiFi case, you have the following players:

• Networking class in sensesp/net/networking.h takes care of the WiFi connectivity
• WSClient class in sensesp/net/ws_client.h manages the SK websocket connection (and the related auth requests).
• SKDeltaQueue in sensesp/signalk/signalk_delta_queue.h manages the outbound message queue.
• SKEmitter (and SKOutput) in sensesp/signalk/signalk_emitter.h (signalk_output.h) serializes data into SK Deltas.

There can be multiple SKDeltaQueue objects (one for each connection method). The queues observe all emitters and stores the deltas in a queue.

WSClient polls the delta queue and if there are any deltas available, sends them to the server.

If you want to do this without WiFi, instantiate your app using SensESPMinimalApp to avoid the Networking and WSCLient objects. Then, you need to instantiate a SKDeltaQueue object manually and poll it repeatedly and send outbound deltas either over the default Serial object or your own Bluetooth serial connection.

Also, for USB serial, you need to disable serial debug logging (or move it over to Serial1).

If you decide to do this, having some output in a form of PR (example code, additional functionality, documentation) would be absolutely great!

[ba58smith]

@janifr , even if you switch to Bluetooth or serial, I think you'll still need to incorporate this PR in order to use any of the ADC2 pins: #642