Question Regarding Heart Rate Sensor

[FrenchBully]

Great stuff, and thanks for putting together such an awesome library. I know you're in the process of expanding the register and was wondering any word on when that will happen? I wanted to be able to add a Heart Rate Sensor, similar to the app they created here. I was trying to use the GPIO, but it seems a little over my head. Any feedback and direction would be greatly appreciated. Thanks in advance for the help.

[brainexe]

Hey @FrenchBully, the GPIO register is currently not really implemented

The job is basically to port the Android implementation to the nodejs GPIO register. But unfortunately I don't have time to do it.

The next step would be to use the analog GPIO input to read out the heart rate, like in the example app code

[FrenchBully]

Unfortunately I wouldn't know where to begin to port it over. Anyway you could expedite the implementation of heart rate sensor? I'm willing to compensate for your time? Thanks again for the help.

[brainexe]

Hey @FrenchBully ,
I just created a new branch, called "gpio" which includes an early version of the GPIO component. Right now I don't have access to a metawear device, so I have no chance for testing and finishing development.

Open steps to do:
Implement missing argument in callbacks for the methods enableNotifications/readAnalogIn/readDigitalIn (see todo). I recommend to implement some logic in examples/gpio.js and add logging for the received "buffer" during development. When you call the script with DEBUG="noble-device" you can check the whole communication in detail.
With buffer.readInt16LE() you can access the data from metawear device. I haven't checked the related android code, but you can take a look here. Just extract the relevant data from the "buffer" and pass it as argument to "callback". This should be only one value?!

When the basic-GPIO functionality is working, you can start developing the logic for the pulse sensor.
Here you can find the android code, which was easier to read for me :)

I guess the rough steps are:

• gpio.enableNotifications(GPIO_PIN) to subscribe pin changes
• with setInterval(50) read gpio.readAnalogIn(GPIO_PIN, gpio.ANALOG_READ_MODE.ADC, callback); you can request the current value each 50ms.
• port callback functionality

But keep in mind, the GPIO branch was created in less than an hour and I have no device for testing. So i promise there are bugs in the code and it will not work out of the box.

I recommend to create a fork from my branch "gpio" and commit you stuff there. Then I can take a look into your implementation and can give some advise when needed.