HC-06 6-Pin Bluetooth Module (V2.0, CSR Chip)

Enter AT command mode before pairing by pulling the KEY pin high (to VCC) or ensuring the module is unpowered, then powering it while KEY is held high. Connect via a serial terminal at the default 9600 baud to send commands like AT+NAME=YourName to rename or AT+BAUDx to change baud rate (where x is a code, e.g., 4 for 9600). Remember to save settings and cycle power for changes to take effect. The KEY pin is typically inactive on slave-only modules like the HC-06.

Yes, you can connect it directly. The module's logic pins (TXD, RXD) are 3.3V tolerant but can typically accept 5V signals from the Arduino's TX pin due to internal protection. For safety, a simple voltage divider or level shifter is recommended for the Arduino TX to module RXD line. Power the module via its VCC pin with a regulated 3.6V to 5V supply, as its onboard LDO will step it down to 3.3V for the radio. Always connect Arduino RX to module TX and Arduino TX to module RX.

The HC-05 can operate as both a master (initiates connections) and a slave, while the HC-06 is strictly a slave-only device, waiting for a master to connect. The HC-05 often includes a button for mode switching and supports more AT commands. The HC-06 is simpler, typically cheaper, and ideal for projects where the module only needs to accept incoming connections from a phone or PC. Both use similar CSR chips and offer Serial Port Profile functionality for transparent wireless UART communication.

A blinking LED indicates the HC-06 is powered on and in discoverable mode but not paired/connected. A solid LED confirms an active Bluetooth connection has been established. You can also use the dedicated STATE pin: it outputs a low logic level when disconnected and switches high when connected. This pin can be read by your microcontroller to automate processes based on connection status, eliminating the need to visually check the LED.