The HobbyKing AIO that I’m using in this project talks MAVLink with the APM console (or any other MAVLink management console). I decided to use BT for connecting it to the console so I borrowed a HC-05 module from my good friend Tomer.
The HC-05 comes configured for 38400 bps (bits per second) so the first step was to configure it to operate at 115200 bps.
Configuration of the HC-05 is done with a FTDI board. I bought one on Ali express for $2.48.
Here are the HC-05 on the right and the FTDI board on the left:
This FTDI board has a switch that sets it to use 3.3V or 5V. Since the HC-05 is sensitive to voltages over 3.3 I used 3.3V.
The HC-05 enters configuration mode (via AT commands) when pin 34 is pulled high. On this board pin 34 is connected to “Key”.
The two boards are connected as follows:
- FTDI ground —> HC-05 ground
- FTDI TX —> HC-05 RX
- FTDI RX —> HC-05 TX
- FTDI VCC —> HC-05 Key
- FTDI VCC —> HC-05 5V
Now the FTDI board can be connected to a USB port and you can use a terminal program (I used Arduino’s serial monitor) to connect to it. Remember that the connection speed is 38400.
Sent “AT” to the board and it should respond with “OK”.
To change the bit rate send “AT+UART=115200,0,0”. The board should respond with “OK” and it is ready.
The data sheet for the HC-05 can be found here.