add GPS Time Server

apps.json

@@ -2369,5 +2369,17 @@
     {"name":"isoclock.app.js","url":"isoclock.js"},
     {"name":"isoclock.img","url":"isoclock-icon.js","evaluate":true}
  ]
+},
+{ "id": "gpstimeserver",
+  "name": "GPS Time Server",
+  "icon": "widget.png",
+  "version":"0.01",
+  "description": "A widget which automatically starts the GPS and turns Bangle.js into a Bluetooth time server.",
+  "tags": "widget",
+  "type": "widget",
+  "readme": "README.md",
+  "storage": [
+    {"name":"gpstimeserver.wid.js","url":"widget.js"}
+  ]
 }
 ]

apps/gpstimeserver/ChangeLog

@@ -0,0 +1 @@
+0.01: New Widget!

apps/gpstimeserver/README.md

@@ -0,0 +1,59 @@
+# GPS Time Server
+
+A widget which automatically starts the GPS and turns Bangle.js into a Bluetooth time server, UUID 0x1805.
+
+Other Espruino Bluetooth devices can then find it and use it to synchronise time.
+
+**Note:** Because GPS is kept on, you'll need to keep your Bangle.js on charge for this to be useful.
+
+## Usage
+
+Just install this widget, and from then on any app which loads widgets will
+display the icon ![](widget.png) in the top left, and Bangle.js will be
+broadcasting the current time to any device that connects.
+
+## Technical
+
+This implements the [Bluetooth Time Service](https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=292957) listed [here](https://www.bluetooth.com/specifications/gatt/).
+
+The Bluetooth docs are verbose and hard to read, so here's a rundown of how it works.
+
+* The Bangle advertises service `0x1805`
+* You connect to it, and request service `0x1805` and characteristic `0x2A2B`
+* A 10 byte array is returned:
+
+```
+[
+  year_lowbyte,
+  year_highbyte,
+  month,
+  day_of_month,
+  hours,
+  minutes,
+  seconds,
+  day_of_week, // 1=monday...7=sunday
+  subseconds, // 0..255
+  update_reason // 0=unknown currently
+]
+```
+
+```
+//NRF.requestDevice({ filters: [{ services: ['1805'] }] }).then(print)
+
+var gatt;
+NRF.connect("c7:4b:2e:c6:f5:45 random").then(function(g) {
+  gatt = g;
+  return gatt.getPrimaryService("1805");
+}).then(function(service) {
+  return service.getCharacteristic("2A2B");
+}).then(function(c) {
+  return c.readValue();
+}).then(function(d) {
+  console.log("Got:", JSON.stringify(d.buffer));
+  var year = d.getUint16(0,1);
+  // ...
+  gatt.disconnect();
+}).catch(function(e) {
+  console.log("Something's broken.",e);
+});
+```

apps/gpstimeserver/widget.js

@@ -0,0 +1,53 @@
+(() => {
+
+function getBLECurrentTimeData(d) {
+  var updateReason = 0; // unknown update reason
+  return [
+      d.getFullYear()&0xFF,
+      d.getFullYear()>>8,
+      d.getMonth()+1,
+      d.getDate(),
+      d.getHours(),
+      d.getMinutes(),
+      d.getSeconds(),
+      d.getDay() ? d.getDay() : 7/*sunday*/,
+      Math.floor(d.getMilliseconds()*255/1000),
+      updateReason
+    ];
+}
+
+NRF.setServices({
+  0x1805 : {
+    0x2A2B : {
+      value : getBLECurrentTimeData(new Date()),
+      readable : true,
+      notify : true
+    }
+  }
+}, {  advertise: [ '1805' ] });
+
+Bangle.on('GPS', function(fix) {
+  if (fix.time !== undefined) {
+    NRF.updateServices({
+      0x1805 : {
+        0x2A2B : {
+          value : getBLECurrentTimeData(fix.time),
+          notify : true
+        }
+      }
+    });
+  }
+});
+Bangle.setGPSPower(1);
+
+
+  function draw() {
+    g.reset();
+    g.drawImage(require("heatshrink").decompress(atob("i0XxH+CR0HhEHEyEOi1AAAMWhAUNisW6/XwICBi0PHpgUC69WAYUWIpcVxAVGsgsLi2sCAOsg4EDiwVPlZYCCoUzss6IwxBE68rDYJBBldlAAVeNpIADNoNdxIWDssrCYMJgKZDF4SZCxGtCollmcJAALFDnTFE1utxNdrtXq9WqwVDeJAVB1tdrwABFgM6maOKwQWCIQgbBmQVJmQVCCwlXF4LoKCoaHDCoSgFAAldCwYtCqxbCLRQVECwNWr4VBr4VJmYWFrpcDCpM6neJC4pdCChEsss7C4+IFRI4DC4LBKCpBQLAAgA=")), this.x, this.y);
+  }
+    WIDGETS["gpstimeserver"]={
+    area:"tl", // tl (top left), tr (top right), bl (bottom left), br (bottom right)
+    width: 24, // how wide is the widget? You can change this and call Bangle.drawWidgets() to re-layout
+    draw:draw // called to draw the widget
+  };
+})()