• Not a problem, I learned something while searching for info about MAC-addresses.

    Especially for other Bluetooth- and JS-newbies like me, below skeleton JS-code can either show the value received, or a simple graph. Just remove/add comments at the show_data- or graph-lines. And here's the Arduino-code I'm using.

    On the JS-side there's for sure room for improvement, one thing that puzzles me is this line g.drawString(" Batt:" + data, 1, g.getHeigth()/2); which should display Batt:nnn where nnn is the value without leading zeros. On the Bangle 2 display is though instead shown b:nnn, so instead of " Batt:" is " b:" shown (lowercase b). The value itself is shown correctly.

    var gatt;
    var history = new Float32Array(64);
    
    
    g.clear();
    
    // Load fonts
    require("Font7x11Numeric7Seg").add(Graph­ics);
    
    function graph(data) {
      // quickly move all elements of history back one
      history.set(new Float32Array(history.buffer,4));
    
      history[history.length-1] = data;
      //
      g.clear();
      // Draw Graph
      var r = require("graph").drawLine(g, history, {
        miny: 26,
        axes : true,
        gridy : 10,
        title: "Battery"
      });
      // Label last reading
      g.setFontAlign(1,-1);
      g.drawString(Math.round(data), r.x+r.w, r.gety(data)+2);
      // Update the screen
      g.flip();
     
    }
    
    function show_data(data) {
      var on = true;
      g.clear();
      g.setFont("7x11Numeric7Seg",3);
      g.drawString(" Batt:" + data, 1, g.getHeigth()/2); 
    
    }
    
    NRF.connect("MA:C-:AD:DR:ES:S! public").then(function(g) {
      gatt = g;
      return gatt.getPrimaryService(0x180F);
    }).then(function(service) {
      return service.getCharacteristic(0x2A19);
    }).then(function(characteristic) {
      characteristic.on('characteristicvaluech­anged', function(event) {
        console.log("battery: "+JSON.stringify(event.target.value.buff­er));
        
        show_data(event.target.value.buffer);
        //graph(event.target.value.buffer);
      });
      return characteristic.startNotifications();
        
      }).then(function() {
      console.log("Done!");
    });
    
    
    
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