Muse S optical sensor support

[kylemath]

Hey @urish can I open this one back up and suggest a feature I can help with to expose the PPG data in the Muse 2 and Muse S headbands.

based on the address of the data in the raw packets here:
#42 (comment)

I think the main parsing of the data files happens here:
https://github.com/urish/muse-js/blob/master/src/muse.spec.ts

I believe a function would be needed here to parse the data, and define data types in another file:
https://github.com/urish/muse-js/blob/master/src/lib/muse-parse.ts

[CaydenPierce]

Giving this a shot.

The characteristic for PPG on Muse are defined here: https://github.com/alexandrebarachant/muse-lsl/blob/master/muselsl/constants.py

One thing worth noting is that things are different between Muse 2 and Muse S for PPG.

Muse 2

PPG_1 - ambient
PPG_2 - infrared
PPG_3 - red

Muse S

PPG_1 - ambient
PPG_2 - green
PPG_3 - ? (all zeros with some random ints every 10 packets or so)

Muse Meditation App

User @chatchavan logged Muse S bluetooth packets from InterAxon Muse application here: ErikBjare/thesis#9

He said they are only using PPG_2 and assumes that it's the green light.

Result

Let's subscribe to and supply PPG_1, PPG_2, and PPG_3. Library users can determine which channel they want to use.

[kylemath]

Good, plan, we should get our hands on a muse S2 and see if its different

[CaydenPierce]

Working on this here: https://github.com/CaydenPierce/muse-js/tree/ppg

[kylemath]

Great