bleno writeup (updated)

Hoshino Aoi

— 4 min read

A Node.js module for implementing BLE (Bluetooth Low Energy) peripherals.

Need a BLE central module? See noble.

Note: macOS / Mac OS X, Linux, FreeBSD and Windows are currently the only supported OSes.

Prerequisites

OS X

  • install Xcode
  • 10.9 or later

Linux

  • Kernel version 3.6 or above
  • libbluetooth-dev
  • bluetoothd disabled, if BlueZ 5.14 or later is installed. Use sudo hciconfig hci0 up to power Bluetooth adapter up after stopping or disabling bluetoothd.
    • System V:
      • sudo service bluetooth stop (once)
      • sudo update-rc.d bluetooth remove (persist on reboot)
    • systemd
      • sudo systemctl stop bluetooth (once)
      • sudo systemctl disable bluetooth (persist on reboot)

If you're using noble and bleno at the same time, connected BLE devices may not be able to retrieve a list of services from the BLE adaptor. Check out noble's documentation on bleno compatibility

Ubuntu/Debian/Raspbian

sudo apt-get install bluetooth bluez libbluetooth-dev libudev-dev

Make sure node is on your path, if it's not, some options:

Fedora / Other-RPM based

sudo yum install bluez bluez-libs bluez-libs-devel

Intel Edison

See Configure Intel Edison for Bluetooth LE (Smart) Development

FreeBSD

Make sure you have GNU Make:

sudo pkg install gmake

Disable automatic loading of the default Bluetooth stack by putting no-ubt.conf into /usr/local/etc/devd/no-ubt.conf and restarting devd (sudo service devd restart).

Unload ng_ubt kernel module if already loaded:

sudo kldunload ng_ubt

Make sure you have read and write permissions on the /dev/usb/* device that corresponds to your Bluetooth adapter.

Windows

Install

npm install bleno

Usage

var bleno = require('bleno');

See examples folder for code examples.

Actions

Advertising

Start advertising

NOTE: bleno.state must be poweredOn before advertising is started. bleno.on('stateChange', callback(state)); can be used register for state change events.

var name = 'name';
var serviceUuids = ['fffffffffffffffffffffffffffffff0']

bleno.startAdvertising(name, serviceUuids[, callback(error)]);

Note:: there are limits on the name and service UUID's

  • name
    • maximum 26 bytes
  • service UUID's
    • 1 128-bit service UUID
    • 1 128-bit service UUID + 2 16-bit service UUID's
    • 7 16-bit service UUID
Start advertising iBeacon
var uuid = 'e2c56db5dffb48d2b060d0f5a71096e0';
var major = 0; // 0x0000 - 0xffff
var minor = 0; // 0x0000 - 0xffff
var measuredPower = -59; // -128 - 127

bleno.startAdvertisingIBeacon(uuid, major, minor, measuredPower[, callback(error)]);

Notes::

  • OS X:
    • in iBeacon mode your peripheral is non-connectable!
Start advertising with EIR data (Linux only)
var scanData = new Buffer(...); // maximum 31 bytes
var advertisementData = new Buffer(...); // maximum 31 bytes

bleno.startAdvertisingWithEIRData(advertisementData[, scanData, callback(error)]);
Stop advertising
bleno.stopAdvertising([callback]);

Set services

Set the primary services available on the peripheral.

var services = [
   ... // see PrimaryService for data type
];

bleno.setServices(services[, callback(error)]);

Disconnect client

bleno.disconnect(); // Linux only

Update RSSI

bleno.updateRssi([callback(error, rssi)]); // not available in OS X 10.9

Primary Service

var PrimaryService = bleno.PrimaryService;

var primaryService = new PrimaryService({
    uuid: 'fffffffffffffffffffffffffffffff0', // or 'fff0' for 16-bit
    characteristics: [
        // see Characteristic for data type
    ]
});

Characteristic

var Characteristic = bleno.Characteristic;

var characteristic = new Characteristic({
    uuid: 'fffffffffffffffffffffffffffffff1', // or 'fff1' for 16-bit
    properties: [ ... ], // can be a combination of 'read', 'write', 'writeWithoutResponse', 'notify', 'indicate'
    secure: [ ... ], // enable security for properties, can be a combination of 'read', 'write', 'writeWithoutResponse', 'notify', 'indicate'
    value: null, // optional static value, must be of type Buffer - for read only characteristics
    descriptors: [
        // see Descriptor for data type
    ],
    onReadRequest: null, // optional read request handler, function(offset, callback) { ... }
    onWriteRequest: null, // optional write request handler, function(data, offset, withoutResponse, callback) { ...}
    onSubscribe: null, // optional notify/indicate subscribe handler, function(maxValueSize, updateValueCallback) { ...}
    onUnsubscribe: null, // optional notify/indicate unsubscribe handler, function() { ...}
    onNotify: null, // optional notify sent handler, function() { ...}
    onIndicate: null // optional indicate confirmation received handler, function() { ...}
});

Result codes

  • Characteristic.RESULT_SUCCESS
  • Characteristic.RESULT_INVALID_OFFSET
  • Characteristic.RESULT_INVALID_ATTRIBUTE_LENGTH
  • Characteristic.RESULT_UNLIKELY_ERROR

Read requests

Can specify read request handler via constructor options or by extending Characteristic and overriding onReadRequest.

Parameters to handler are

  • offset (0x0000 - 0xffff)
  • callback

callback must be called with result and data (of type Buffer) - can be async.

var result = Characteristic.RESULT_SUCCESS;
var data = new Buffer( ... );

callback(result, data);

Write requests

Can specify write request handler via constructor options or by extending Characteristic and overriding onWriteRequest.

Parameters to handler are

  • data (Buffer)
  • offset (0x0000 - 0xffff)
  • withoutResponse (true | false)
  • callback.

callback must be called with result code - can be async.

var result = Characteristic.RESULT_SUCCESS;

callback(result);

Notify subscribe

Can specify notify subscribe handler via constructor options or by extending Characteristic and overriding onSubscribe.

Parameters to handler are

  • maxValueSize (maximum data size)
  • updateValueCallback (callback to call when value has changed)

Notify unsubscribe

Can specify notify unsubscribe handler via constructor options or by extending Characteristic and overriding onUnsubscribe.

Notify value changes

Call the updateValueCallback callback (see Notify subscribe), with an argument of type Buffer

Can specify notify sent handler via constructor options or by extending Characteristic and overriding onNotify.

Descriptor

var Descriptor = bleno.Descriptor;

var descriptor = new Descriptor({
    uuid: '2901',
    value: 'value' // static value, must be of type Buffer or string if set
});

Events

Adapter state change

state = <"unknown" | "resetting" | "unsupported" | "unauthorized" | "poweredOff" | "poweredOn">

bleno.on('stateChange', callback(state));

bleno.on('advertisingStart', callback(error));

bleno.on('advertisingStartError', callback(error));

bleno.on('advertisingStop', callback);

Services set

bleno.on('servicesSet', callback(error));

bleno.on('servicesSetError', callback(error));

Accept

bleno.on('accept', callback(clientAddress)); // not available on OS X 10.9

Disconnect

bleno.on('disconnect', callback(clientAddress)); // Linux only

RSSI Update

bleno.on('rssiUpdate', callback(rssi)); // not available on OS X 10.9

Running on Linux

Note: Make sure you've also checked the Linux Prerequisites

Running without root/sudo

Run the following command:

sudo setcap cap_net_raw+eip $(eval readlink -f `which node`)

This grants the node binary cap_net_raw privileges, so it can start/stop BLE advertising.

Note: The above command requires setcap to be installed, it can be installed using the following:

  • apt: sudo apt-get install libcap2-bin
  • yum: su -c \'yum install libcap2-bin\'

Multiple Adapters

hci0 is used by default to override set the BLENO_HCI_DEVICE_ID environment variable to the interface number.

Example, specify hci1:

sudo BLENO_HCI_DEVICE_ID=1 node <your file>.js

Set custom device name

By default bleno uses the hostname (require('os').hostname()) as the value for the device name (0x2a00) characterisic, to match the behaviour of OS X.

A custom device name can be specified by setting the BLENO_DEVICE_NAME environment variable:

sudo BLENO_DEVICE_NAME="custom device name" node <your file>.js

or

process.env['BLENO_DEVICE_NAME'] = 'custom device name';

Set Advertising Interval

bleno uses a 100 ms advertising interval by default.

A custom advertising interval can be specified by setting the BLENO_ADVERTISING_INTERVAL enviroment variable with the desired value in milliseconds:

sudo BLENO_ADVERTISING_INTERVAL=500 node <your file>.js

Advertising intervals must be between 20 ms to 10 s (10,000 ms).

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