HC-05 TTL Bluetooth Transceiver Module (Without Button)

Enter AT command mode by holding the KEY pin high (or connecting to VCC) during power-up, then use a serial terminal at 38400 baud (default). Send 'AT+ROLE=1' to set as Master or 'AT+ROLE=0' for Slave. Remember to save the configuration with 'AT+SAVE' before exiting. The module will reboot and apply the new role for subsequent pairing and connections.

Connect VCC to Arduino 3.3V, GND to GND. For serial communication, link the HC-05's TX pin to Arduino's RX (Pin 0) and the HC-05's RX pin to Arduino's TX (Pin 1). If you need to send AT commands, connect the KEY pin to a digital I/O pin (e.g., Pin 2) to pull it high for command mode entry. Ensure you use a software serial library to avoid conflicts with the hardware serial used for programming.

Yes, the UART baud rate is configurable via AT commands. In command mode, use 'AT+UART=115200,0,0' to set it to 115200 bps (1 stop bit, no parity). The first parameter is the baud rate, the second is the stop bit (0 for 1 bit), and the third is parity (0 for none). You must set your host microcontroller's serial port to match this baud rate for successful communication after the change.

The HC-05 draws approximately 50 mA during active data transmission at its maximum 4dBm output power. In connected but idle states, consumption is lower. The typical open-space range is 8 to 10 meters, though walls and RF interference can reduce this. For battery-powered projects, consider implementing sleep modes via host MCU control, as the module itself lacks deep sleep functionality in its standard firmware.