Get information about available Bluetooth devices

Before setting up a connection in MATLAB, the NXT brick has to be paired with your computer. Once this is done, the device will be visible in MATLAB.

To get a list of all the available Bluetooth devices use the instrhwinfo command. Get the "friendly" names of the Bluetooth devices available using the RemoteNames field from the output of instrhwinfo.

bluetoothDevices = instrhwinfo('Bluetooth')

remoteNames = bluetoothDevices.RemoteNames

bluetoothDevices = 

        RemoteNames: {'NXT'}
          RemoteIDs: {'btspp://00165310E7C4'}
    BluecoveVersion: 'BlueCove-2.1.1-SNAPSHOT'
     JarFileVersion: 'Version 3.2'


remoteNames = 

    'NXT'

View details of the NXT brick

Get the details of the NXT brick.

deviceInfo = instrhwinfo('Bluetooth','NXT')

deviceInfo = 

               RemoteName: 'NXT'
                 RemoteID: 'btspp://00165310E7C4'
    ObjectConstructorName: {'Bluetooth('NXT', 1);'}
                 Channels: {'1'}

Set up a connection to the NXT brick

The device's RemoteName is NXT and its Channel is 1. Construct a bluetooth object called bt as shown by the ObjectConstructorName in the previous step.

bt = Bluetooth('NXT', 1);

Now connect to the device.

fopen(bt);

Get information about the Lego Mindstorms NXT brick

The Lego Mindstorms data sheet defines a protocol for communicating with NXT brick. It specifies that to get the device information, the command should have following format:

Using this information, raw data packet is formed which is sent to the NXT brick.

This translates the raw data packet to be: [2 0 1 155]. Write this data to the brick.

fwrite(bt,[2 0 1 155]);

The device then gives a response containing device information. The response has following format:

Now read the response from the brick to get its information

btResponse = fread(bt,32)'

btResponse =

  Columns 1 through 13

    33     0     2   155     0    78    88    84     0     0     0     0     0

  Columns 14 through 26

     0     0     0     0     0     0     0     0    22    83    16   231   196

  Columns 27 through 32

     0     0     0     0     0   132

In this example, the response from the NXT brick is:

Let us now read only the name of the brick from its response. We know that bytes 6 to 20 correspond to the brick's name.

btName = char(btResponse(6:20))

btName =

NXT            

Clear the buffer of the Bluetooth object

flushinput(bt);

Play a tone on Lego Mindstorms NXT brick

Let us now play a tone at frequency 1500 Hz for 1000 ms on the brick. The Lego Mindstorms NXT direct commands define a command to play a tone on the brick as follows:

In this example, the raw data packet is formed as follows:

Hence the command to be written to the brick is [6 0 0 3 220 5 232 3].

fwrite(bt,[6 0 0 3 220 5 232 3]);

In addition to the audio tone played on the NXT brick, the device also gives a 5 byte response. Let us now read the response from the brick. The response has the following format:

btResponse = fread(bt,5)'

btResponse =

     3     0     2     3     0

In this example, the response from the NXT brick is:

Close the connection to the NXT brick

fclose(bt);
delete(bt);
clear('bt');

You can get more information on communicating with Lego Mindstorms NXT using high level commands here.