Pinout
HC-05 / HC-06 Bluetooth serial module (ZS-040) pinout
Pins
- EN / KEY (hold high at power-up — or hold the button — to enter AT command mode at 38400 baud)
- VCC (3.6–6V typical — check your specific board)
- GND
- TXD (module → MCU RX, 3.3V logic)
- RXD (MCU TX → module — module RX is 3.3V, use a divider/level shifter from a 5V MCU)
- STATE (goes high once paired/connected, on most boards)
Specifications
| Bluetooth | v2.0 + EDR, Classic SPP (no BLE) |
|---|---|
| Role | HC-05 master/slave; HC-06 slave only |
| Frequency | 2.4 GHz |
| Range | ≈ 10 m (Class 2) |
| Supply (breakout) | 3.6–6 V (onboard 3.3 V regulator) |
| Logic level | 3.3 V (RXD needs a divider from 5 V) |
| Default baud rate | 9600 (HC-05 AT mode: 38400) |
| Default PIN | 1234 |
| Interface | UART |
Notes
- The LED tells the mode: fast blink = waiting to pair, slow double-blink = connected, 2 s blink = AT mode.
- The HC-06 is the slave-only sibling on the same carrier: same pins, but no STATE/EN function on most boards and AT commands without line endings.
