I recently purchased the HC-05 RS232 serial bluetooth module from eBay. These modules sells from $10 to $20 including shipping. My plan was to use it as a economic wireless communication tool between PC and the Arduino board. The module has built-in Serial<–>Bluetooth protocol converter. Therefore it can be connected directly to Arduino serial pins without any ttl level translator chip and with a few external components. One thing to note though, the seller I purchased the module from on ebay had the wrong schematic posted on the listing which was meant for a older version of this module. So depending on which version you have, you will have slightly different pin connection for the AT command enable pin and led indicator pins. The major difference between the two version of the module is, the newer version works in both master and slave mode depending on how you set it up via AT commands and improved firmware. The specification of this module is as follows:
● Bluetooth protocol: Bluetooth Specification v2.0+EDR
● Frequency: 2.4GHz ISM band
● Modulation: GFSK(Gaussian Frequency Shift Keying)
● Emission power: ≤4dBm, Class 2
● Sensitivity: ≤-84dBm at 0.1% BER
● Speed: Asynchronous: 2.1Mbps(Max) / 160 kbps, Synchronous: 1Mbps/1Mbps
● Security: Authentication and encryption
● Profiles: Bluetooth serial port
Power supply: +3.3VDC 50mA
Working temperature: -20 ~ +75 Centigrade
Dimension: 26.9mm x 13mm x 2.2 mm
Here are the data sheet, example schematic for this module:
The schematic I used to connect to arduino is as follows:
This can be used as a cheap way to talk to your Arduino wirelessly and debug your quad copter over serial port without using the relatively expensive XBee modules, even though you will not get as much range as the XBees.
Here is my version of the break out board.
Figure: Front side of the break out board.
Figure: Back side of the break out board.
Testing the module with MultiWii quad and configuration tool: