This is tool for configuring and communicationg with cheap Bluetooth modules HC-05. This firmware was mainly tested on Arduino Nano but should work on any Arduino.

• echo - run echo server. It is useful to check if your module is working. You run this command, connect to the module with your phone or PC and start sending some text to it. The module will receive the text, send it to Arduino, Arduino will send it back to the module and then module will send it back to you.
• atmode - switch HC-05 into AT command mode. The Arduino will just into serial passtrhogh device between your PC and HC-05. This allow you to communicate with Bluetooth module without any additional hardware (with the exception of Arduino of course). You can test if it works by sending AT command which should be answered with OK.
• master <MAC-of-slave> <name> <baudrate> - configure connected HC-05 module as Bluetooth master. It has two parameters. The first one is MAC address of the bluetooth device to which you want your module to connect immediately after boot. Note that MAC address should be in the following form 1234:12:123456 - not like classical one with lot of :. The second parameter is just Bluetooth name of your HC-05 module. Pretty useful to distinguish it from other HC-05 slaves. The last argument is baudrate of the UART.
• slave <name> <baudrate> - configure connected HC-05 module as Bluetooth slave. The same as for master you can configured name of the module. The last argument is baudrate of the UART.
• name <name> - change Bluetooth name of the module.
• baudrate <baudrate> - change baudrate of the module. This baudrate is used when module communicates with Arduino.

• How to connect HC-05 to Linux PC
• Platformio
• HC-05