| Serial number | Pin | Pin direction | Remark |
| 1 | M0 | Input (very weak pull-up) | Determine the two working modes of the module: low level is the transmission mode, and high level is the configuration mode. (Cannot be left floating, can be grounded if not used) |
| 2 | LOCK | output | Module synchronization indication. A high level indicates that both parties are synchronized and data transmission is possible. A low level indicates that the two parties are not synchronized. Transmitting data at this time will result in data loss. |
| 3 | RXD | enter | TTL serial port input, connected to the external TXD pin (can be configured as open-drain or pull-up input, see manual for details) |
| 4 | TXD | output | TTL serial port output, connected to the external RXD pin (can be configured as open-drain or push-pull output, see manual for details ) |
| 5 | TO | output | Indicates the working status of the module, the user wakes up the MCU externally, and outputs low level during power-on self-test initialization. |
| 6 | VCC | enter | Module power supply positive reference, voltage range: 2.8V~5.5V DC |
| 7 | GND | enter | Module ground wire |
| 8 | Fixing hole |
| Fixing hole |
| 9 | Fixing hole |
| Fixing hole |
| 10 | Fixing hole |
| Fixing hole |
| 11 | Fixing hole |
| Fixing hole |
| 12 | Fixing hole |
| Fixing hole |
| 13 | Fixing hole |
| Fixing hole |
| 14 | Fixing hole |
| Fixing hole |
| 15 | Fixing hole |
| Fixing hole |
