This document describes the bluetooth module included with LEDI. There are two different kinds of modules: HC-05 and HC-06. Contrary to what the model number might suggest, the lower numbered model, HC-05 is the more "advanced" module.

The model HC-05 is both master and slave bluetooth device, whereas HC-06 is slave-only. Both modules have factory setting of 9600 baudrate.

There are two different kinds of modules that look exactly the same:

• HC-05 Master and Slave module
• HC-06 Slave-only module

Externally, these modules look identical. Simply from inspection, you cannot tell them apart. As far as the hardware is concerned, both of these modules seem to have identical components. The root of the differences lie in the firmware of these modules.

The module has a lot more accessible pins that what it requires. Many of these PINs are general I/O pins and seem to be controlled from the firmware. Essentially, the differences between the two modules are:

• Slightly different recommended electrical wiring
• Default device name (HC-06 is linvor, HC-05 seem varied)
• Ways of entering AT modes
• Supported AT commands

Testing Connection from PC Bluetooth

This is tested on Ubuntu. If you have bluetooth in your hardware you can readily do this.

First scan to see if you can detect LEDI:

hcitool scan

And now edit /etc/bluetooth/rfcomm.conf and put in an entry like this:

rfcomm0 {
  # Automatically bind the device at startup
  bind no;

  # Bluetooth address of the device
  device 00:12:07:11:13:60;

  # RFCOMM channel for the connection
  channel 1;

  # Description of the connection
  comment "any description you like";
}

Once that’s done, run:

sudo rfcomm release rfcomm0 # if already connected
sudo rfcomm bind rfcomm0
sudo rfcomm connect rfcomm0

A PIN request popup window will show. Put in 1234 and you will pair with LEDI. Now, you can use the rfcomm like a serial port device:

sudo minicom -D /dev/rfcomm0 -b 9600 -8

Changing The Module Configuration

In most cases, changing configuration parameters on HC-05/06 is not required. However, there are several useful things you can do with config change:

• Increase the baud rate, thereby making UART communication faster
• Change the bluetooth module name
• Change the pairing PIN code
• Change pairing behavior (HC-05 only)

Learning The AT Commands

The command set is quite different between HC-05 (master,slave) and HC-06 (slave-only).

# install the prerequisites
sudo apt-get install libqt4-dev
sudo apt-get install libudev-dev
sudo apt-get install libqwt-dev

# install qtserial port
cd $HOME/git
git clone git://gitorious.org/qtplayground/qtserialport.git
cd qtserialport
qmake
make
sudo make install

# now install qSerialTerm
cd $HOME/git
git clone git://github.com/JorgeAparicio/qSerialTerm.git
cd qSerialTerm
qmake
make
sudo make install

Good Resources

• This link shows how o communicate against HC-06 module from a PC