bluetooth - Using Evothings JavaScript to read BLE characteristic data -


i have ble (bluetooth 4.0)pedometer device want read characteristic data using evothings plugin (which uses javascript api interact device)

i using following code - callback when device connected =

function deviceconnected(device) {     console.log('connected device: ' + device.name)     console.log('reading services... have patience!')     device.readservices(         null, // null means "read services".          readallservicescharacteristicsandnotifications,         // listallservicescharacteristicsdescriptors,         readserviceserror) }

callback code readallservicescharacteristicsandnotifications -

function readallservicescharacteristicsandnotifications(device) {     // data each service    console.log('number of services ' + device.__services.length)    console.log('number of characteristic ' + device.__services[0].__characteristics.length)         //var characteristic = service.__characteristics[characteristicuuid]         device.readcharacteristic(         device.__services[0].__characteristics[8]['uuid'],         function (data) {             var test = new uint8array(data);             var result = "";             (var = 0; < test.length; i++) {                 console.log('data  element ' + test[i]);                 console.log('data  element string ' + string.fromcharcode(parseint(test[i], 2)));                 result += string.fromcharcode(parseint(test[i], 2));             }              console.log('data  ' + result);         },         function (errorcode) {         console.log('ble readcharacteristic error: ' + errorcode);      }); }

i think ble data formatsuggests data exchanged binary code bytes. see value in byte array don't know how interpret it.

has used evothings javascript interact ble device?

h i, data received in javascript on ble byte buffer.

see if can find documentation pedometer. lookup @ format of data sent pedometer. access data in buffer accordingly.

here examples.

access byte values in data buffer:

var buf = new uint8array(data); var value1 = buf[0]; var value2 = buf[1];

to 16-bit value use bitwise or, example:

var value = buf[0] | (buf[1] << 8);

depending on data being little endian or big endian, bitwise or needs done in different ways.

here library can use has functions accessing values in byte buffer: https://github.com/evothings/evothings-examples/blob/master/resources/libs/evothings/util/util.js

here example:

// signed int value in buffer thats starts @ // byte index 2 (the int value represented byte 2 , 3). var value = evothings.util.littleendiantoint16(data, 2)

hope helps!


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