mbed Cloud Bluetooth Devicelink

This is an experimental way to connect Bluetooth Low Energy devices into mbed Device Connector and mbed Cloud.

Setup

1. Install mbed Cloud Linux Devicelink.
   • You can run mbed Cloud Linux Devicelink in an Ubuntu VM and this application on your main OS.
2. Install node.js 6+.

Then, on Ubuntu/Debian:

$ sudo apt-get install libudev-dev
$ npm install
$ node bt.js

On macOS:

$ npm install
$ node bt.js

mbed CloudBluetooth Devicelink opens a webserver on localhost:3000 and a TCP socket on localhost:1337. Start mbed Cloud Linux Devicelink and connect it to the TCP socket to bridge the devices into mbed Device Connector.

Now navigate to the web interface at http://localhost:3000 and add your device.

Note on macOS: If you don't see any devices, and --log-seen-devices yields your device with an 'unknown' MAC address; start the process with --mac-os-fix once, then start the process normally.

Options

• --log-seen-devices - logs all devices seen, useful for debugging.

Mapping from BLE to LWM2M

Because BLE devices use GATT services and characteristics and mbed Device Connector uses LWM2M resource models, we need to define a mapping between the two.

In the web interface there are two editors, one for read-mappings and one for write-mappings. In both of these you can use JavaScript to write the mappings.

Known-services

You can re-use mappings. See the 'webserver/public/known-services' folder. If Bluetooth Devicelink encounters these services it will autogenerate the mapping.

Read mapping

Defines what should happen when translating BLE GATT characteristic value into LWM2M resource value. Is automatically called when a BLE NOTIFY event happens as well.

{
    // led/0/color is LWM2M resource here

    "led/0/color": function (m) {
        // m contains the full BLE GATT model (e.g. m['180a'] is the 180a service)
        // and m['180a']['2a29'] is char 2a29 under that service
        // Characteristics always return a Buffer, so you'll need to do some work to 'un-buffer' it.

        // read characteristics like: m['180a']['2a29'].toString('ascii'))
        var a = m['9900']['9901'];
        return (a[2] << 16) + (a[1] << 8) + a[2];
    }
}

Write mapping

Defines what should happen when a resource was updated in mbed Device Connector, and what command should be sent to the BLE device.

{
    // actuator/0/action is the LWM2M resource

    "actuator/0/action": function (value, write) {
        // 'value' contains the new value (seen from Connector) as a *string*
        // write is a function which you can use to write to a characteristic. it has 2 arguments
        //    * BLE path => '180a/2a29' for char 2a29 under service 180a
        //    * Buffer => array of bytes to be sent to this characteristic
        // example: write('180a/2a29', [ 0x10, 0x30 ])

        var v = Number(value);

        write('9900/9901', [ 0x23, v ]);
    }
}

TODO

• Can only connect to unprotected devices (no security features).
• status-change events are not handled.