Fun with Bluetooth @ Amsterdam JSNation

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fun with bluetooth

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why?

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progressive   web apps

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pwa’s are great !

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but...

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but...

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bluetooth

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bluetooth sucks

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classic bluetooth the reason everybody   hates bluetooth bluetooth low energy vs. control drones and other cool shit

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bluetooth low energy also known as BLE Bluetooth LE Bluetooth Smart Bluetooth 4

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bluetooth low energy also known as BLE Bluetooth LE Bluetooth Smart Bluetooth 4 and 5

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10 million   bluetooth devices  shipping every day

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mobile phone

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computer

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glucose monitor somebody's hand

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activity tracker

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playbulb sphere playbulb

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spherio bb-8

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parrot mini drone

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ﬁdget spinner

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the boring theoretical stuff

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central peripheral

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central

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generic attribute proﬁle

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generic attribute proﬁle ?

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generic attribute proﬁle gatt, because gap was already taken

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central peripheral client server

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server service characteristic value array of objects object property value

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services and characteristics are identiﬁed by uuid’s 16 bit or 128 bit

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read write write without response notify each characteristic supports one or more of these

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every value is an array of bytes no fancy datatypes, just bytes

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pfew...

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fun with bluetooth boring facts  about

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fun with bluetooth

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web  bluetooth api still not the fun part :-(

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connecting to a device

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navigator.bluetooth.requestDevice({ filters: [ { namePrefix: 'PLAYBULB' } ], optionalServices: [ 0xff0f ] }) .then(device => device.gatt.connect()) .then(server => server.getPrimaryService(0xff0f)) .then(service => service.getCharacteristic(0xfffc)) .then(characteristic => { return characteristic.writeValue( new Uint8Array([ 0x00, r, g, b ]) ); }) we tell the browser what   kind of device we want

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the user selects the actual device

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navigator.bluetooth.requestDevice({ filters: [ { namePrefix: 'PLAYBULB' } ], optionalServices: [ 0xff0f ] }) .then(device => device.gatt.connect()) .then(server => server.getPrimaryService(0xff0f)) .then(service => service.getCharacteristic(0xfffc)) .then(characteristic => { return characteristic.writeValue( new Uint8Array([ 0x00, r, g, b ]) ); }) get the characteristic get the service connect to the server

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writing data

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reading data

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navigator.bluetooth.requestDevice({ ... }) .then(device => device.gatt.connect()) .then(server => server.getPrimaryService(0xff0f)) .then(service => service.getCharacteristic(0xfffc)) .then(c => c.readValue()) .then(value => { let r = value.getUint8(1); let g = value.getUint8(2); let b = value.getUint8(3); }) read some bytes

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get notiﬁed of changes

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navigator.bluetooth.requestDevice({ ... }) .then(device => device.gatt.connect()) .then(server => server.getPrimaryService(0xff0f)) .then(service => service.getCharacteristic(0xfffc)) .then(c => { c.addEventListener('characteristicvaluechanged', e => { let r = e.target.value.getUint8(1); let g = e.target.value.getUint8(2); let b = e.target.value.getUint8(3); }); c.startNotifications(); }) add event listener don't forget to start listening

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custom characteristics. wtf!

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insert xkcd comic about standards here

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writing a value: function(r, g, b) { return new Uint8Array([ 0x00, r, g, b ]); } reading a value: function(buffer) { return {   r: buffer.getUint8(1),   g: buffer.getUint8(2),   b: buffer.getUint8(3)   } } writing to and reading  from the same characteristic

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writing a value: function(r, g, b) { return new Uint8Array([ 0x01, g, 0x01, 0x00, 0x01,   b, 0x01, r, 0x01, 0x00   ]); } reading the current   color is not possible

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writing a value:   function(r, g, b) { var buffer = new Uint8Array([   0xaa, 0x0a, 0xfc, 0x3a, 0x86, 0x01, 0x0d,   0x06, 0x01, r, g, b, 0x00, 0x00,   (Math.random() * 1000) & 0xff, 0x55, 0x0d   ]); for (var i = 1; i < buffer.length - 2; i++) { buffer[15] += buffer[i]; } return buffer; } reading the current   color is not possible

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writing a value:   function(r, g, b, position) { let buffer = new Uint8Array([ 0x07, 0x02, position + 1, r, g, b ]); return buffer; }

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writing a value:   function(r, g, b, position) { let buffer = new Uint8Array([ 0x58, r, g, b, 0x01, position ]); ...

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writing a value:   function(r, g, b, position) { let buffer = new Uint8Array([ 0x58, r, g, b, 0x01, position ]); let payload = new Uint8Array(buffer.length + 4); payload[0] = payload.length - 2; payload[1] = payload.length - 2 >>> 8; payload.set(buffer, 2); let checksum = payload.reduce((a, b) => a + b, 0); payload[payload.length - 2] = checksum; payload[payload.length - 1] = checksum >>> 8; let extra = payload.filter(value => { 

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message[m] = 0x03; message[m + 1] = 0x05; m += 2; } else if (payload[i] === 0x03) { message[m] = 0x03; message[m + 1] = 0x06; m += 2; } else { message[m] = payload[i]; m++; } } message[0] = 0x01; message[message.length - 1] = 0x02; return message; }

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adafruit  bluetooth   sniffer

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decompiling   the apk don't tell anyone!

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demo ﬁnally the fun part

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warning experimental technology  setting low expectations

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warning wiﬁ interference  lowering them even further

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https:/ /bluetooth.rocks/lightbulb  https:/ /github.com/BluetoothRocks/Lightbulb change the colour   of a lightbulb

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https:/ /bluetooth.rocks/pixel  https:/ /github.com/BluetoothRocks/Matrix draw pixel art on   a led matrix display

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https:/ /bluetooth.rocks/racer https:/ /github.com/BluetoothRocks/Racer control a lego racer   using a gamepad use css animations to   deﬁne a path

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https:/ /bluetooth.rocks/drone  https:/ /github.com/BluetoothRocks/Drone control a drone   from your browser

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https:/ /bluetooth.rocks/pulse  https:/ /github.com/BluetoothRocks/Pulse ﬁnd out your   current heartbeat