Question regarding the capabilities of js2 for my usecase

[landstreik]

Hey everyone!

I am looking for a BLE device with PPG or ECG sensors to feed my little Android app with realtime HR data. I am not just looking for the current BPM value but I want to know the exact timing and synchronize events in my app to my heart. I know I will need to predict the incoming beats to make up for any latency along the chain. I want to read the data from the (bangle.js 2?) sensor, send it to my Android phone (Fairphone 4), process it in my app (Kotlin / Compose) and control another BLE device accordingly. Imagine setting up a metronome that is always on time with my heart.

Is the bangle.js 2 the right device for my case? If not can you recommend alternatives? I was also looking into the "HealthyPi Move" but I also don't want to go over the top. This is just for entertainment purposes, not medical and I am not experienced with this stuff.

I would love to get your opinions and please be kind to me. English is not my first language and I'm new to app development, GitHub and this community. Thanks!

[gfwilliams]

Hi!

The Bangle's built-in heart rate sensing algorithm gives you a BPM value but not a notification for each beat. However you can access the raw data very easily and could actually do your own detection in a few lines.

For example if you look at the screenshot for the HRM app: https://banglejs.com/apps/?id=hrm

You can see down the bottom there's the PPG data, and you'd basically just want to detect when the PPG value crosses the midpoint. I'm happy to help with some example code if you need it, or you could just stream the PPG value direct to your app and process it there.

As you may have seen from some posts on here, the Bangle's HRM isn't the best that's available. However if you're not planning on moving around a lot it works well enough, and I feel like it'd be pretty easy to set up to work with with your app.

One more thing to add is if you've just got 2 BLE peripherals you're connecting to, you could take a look at Web Bluetooth on a website - especially if you're not that well versed in Android development. It's really quick to be able to develop it on your desktop and then just run on your phone as and when you need it