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add GPS Time Server
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gfwilliams committed Nov 16, 2020
1 parent ae5b7ba commit 24c84f9ba6a42d0d5aeda4743243d80f3fd7cb48
@@ -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"}
]
}
]
@@ -0,0 +1 @@
0.01: New Widget!
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# 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);
});
```
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(() => {

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
};
})()
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