Puck.js HRM

[edwardgalligan]

I've been reading this thread on Bangle.js HRM support. Given all the info I've read there, & that the support for VC31B + blobs is in Espruino (in a relatively non-Bangle.js-specific way - e.g. hrm_get_hrm_info) - I'm trying to get a sense of how viable would it be to put together a sort of "Puck.js HRM" with the VC31B.

I understand VCare is a Vietnamese manufacturer that doesn't seem to sell through consumer-facing channels, so sourcing hardware may be difficult.

Thoughts/questions

• if VC31B were attainable, I presume this would need a custom PCB with Bluetooth Beacon Kit - this isn't something that could be worked into puck.js itself.
• using an alternative consumer-available HRM modules would require working some support into Espruino & recompiling it.

Am I missing anything here or incorrect on any assumptions?

[gfwilliams]

We do actually have JS modules to handle interfacing to heart rate sensors already - which are more readily available):

• https://www.espruino.com/BH1792
• https://www.espruino.com/MAX30102

The MAX30102 one even has a link to ebay where you can buy the modules on breakout boards, which you could wire to the Puck.

Having said that, those modules only give your raw IR data and the algorithm is up to you. You could:

• maybe feed it into the VC31 binary algo
• use the 'open' version that's also in the Bangle.js repo
• Make your own one - Espruino has FFT built-in so you could just run that over it to pull out the main frequencies
• Feed the data to a PC/some other device where you do the number crunching

There are other concerns though - you need to package the sensor up so you don't get light bleed, have a way to hold the puck onto your wrist (there is a 3d printable case for this) and then battery usage could also be an issue.

All told IMO you'd have to have a very good reason to want to use a Puck over a Bangle.js which does it all for you :)