The HC-05 is a classic Bluetooth 2.0 SPP (Serial Port Profile) module that creates a wireless UART bridge. It can operate in both master and slave modes, making it useful for wireless serial communication with smartphones and computers.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | STATE | Connection status indicator | I/O |
| 2 | RXD | UART receive (5V tolerant) | BUS |
| 3 | TXD | UART transmit 3.3V | BUS |
| 4 | GND | Ground | GND |
| 5 | VCC | Power supply 3.6V–6V | PWR |
| 6 | EN | AT command mode, HIGH = AT mode | I/O |