Add speed/cadence sensor

[mattdsteele]

Hi!

This was my first attempt at working with ANT+, as well as my first time doing anything even remotely low-level with JavaScript. So I'm probably getting a few things wrong.

In particular, I'm not so sure what data I'm actually getting back when I receive the CHANNEL_TYPE_ONEWAY_RECEIVE event. It's 3 bytes long but the spec sheet doesn't show anything like that being broadcast on the channel. It seems to always be consistent, so I'm treating it as the DeviceID, which might be completely false! If you're aware of what's actually being broadcast here, I'm happy to fix it up.

Spec sheet: https://www.thisisant.com/resources/bicycle-speed-and-cadence/

Closes #3

[Loghorn]

Hi @mattdsteele
thank you for your work.

You can safely ignore the CHANNEL_TYPE_ONEWAY_RECEIVE event: it is used for diagnostic purposes and is not defined by ANT+ protocol (it's probably used by your device manufacturer for its own purposes) so please remove it from the handling function.

Also, you should handle the deviceId === 0 case like it's done in the hearth rate sensor, by sending a MESSAGE_CHANNEL_ID request, because ANT+ dictates that the device id 0 must be used only for pairing (i.e. finding the actual device id).

Finally, it would be awesome if you could also add the scanner for speed/cadence: I could do it based on what you already implemented, but unlike myself you can actually try it 😄

[mattdsteele]

@Loghorn done, feel free to check it out now.

The scanner code wasn't too bad once I extracted the common code out, and it works great. And you're right, sending the MESSAGE_CHANNEL_ID allowed me to get the non-0 channel ID - I think this will help stabilize the runtime behavior quite a bit!

Let me know if there's anything else you'd like added/tested.

[Loghorn]

Thank you very much