Advertise Mag reading when button pushed

Is there a tutorial, that I can't find, that shows code to advertise the magnetometer values in a characteristic when the button is pushed?

Thank you.

There isn't, but try:

setWatch(function() {
  var m = Puck.mag();
  NRF.setAdvertising({
    0x1809 : [m.x>>8,m.x,m.y>>8,m.y,m.z>>8,m.z]
  });
}, BTN, {repeat:true,debounce:50,edge:"rising"});

That should pack the magnetometer data into 6 bytes that you could then read. Hope that helps!

Thank you for the code sample, I will put it into place tonight.

Hi Gordon,

On Puck we have: [-21, -5126,5,1289, -3,-747]
On RPi3 we have: [235, 250,5, 9,253, 21]

How can we obtain the advertised mag values ?

In JavaScript?

It seems I got the endianness wrong, so you can't just do: new Int16Array((new Uint8Array([235, 250,5, 9,253, 21])).buffer)

Instead you need:

var a = [235, 250,5, 9,253, 21];
var d = [(a[0]<<8)|a[1], (a[2]<<8)|a[3], (a[4]<<8)|a[5]];
for (var i=0;i<3;i++) if (d[i]&32768) d[i]-=65536;
// results in d

I guess you're using Java in Android - that code should be pretty easy to convert.

There are other ways of converting numbers from byte arrays (utilities in various different languages), but the code above is pretty universal.

Hi Gordon,

Thank you for your answer. Yes, one way of getting the data on Android is:

int value = new BigInteger(new byte[]{a[i], a[i + 1]}).intValue();

Hi @Gordon

How did you test the advertising? I'm trying to test it using a WiPy and the nRF connect app, but I don't see any data.

Personally I use the NRF Connect app to scan for advertising data.

You're trying to scan for advertising data that's coming from a Puck.js?

Are you disconnected from the Puck.js? Puck.js (like most BLE devices) will only advertise when there is no device with an active BLE connection to it.

Yes, I'm trying to scan for advertising data that's coming from my Puck.js.

I indeed had a Bluetooth connection open (for the IDE). Thank you!