| Pin number |
Pin name |
Type |
Pin usage |
| 1 |
GND |
input |
Module ground wire |
| 2 |
GND |
input |
Module ground wire |
| 3 |
RESET |
input |
Module reset pin |
| 4 |
AUX |
output |
Used to indicate the working status of the module; the user wakes up the external MCU and outputs low level during power-on self-test initialization; (can be left floating) |
| 5 |
TXD |
output |
TTL serial port output, connected to the external RXD input pin; |
| 6 |
RXD |
input |
TTL serial port input, connected to the external TXD output pin; |
| 7 |
M1 |
input |
Cooperate with M0 to determine the 4 working modes of the module (cannot be left floating, can be grounded if not used) |
| 8 |
GND |
input |
Module ground wire |
| 9 |
GND |
input |
Module ground wire |
| 10 |
M0 |
input |
Cooperate with M1 to determine the 4 working modes of the module (cannot be left floating, can be grounded if not used) |
| 11 |
3.3V |
– |
No need to care, leave it hanging |
| 12 |
GND |
input |
Module ground wire |
| 13 |
SWCLK |
– |
No need to care, leave it hanging |
| 14 |
SWDIO |
– |
No need to care, leave it hanging |
| 15 |
NC |
– |
No need to care, leave it hanging |
| 16 |
NC |
– |
No need to care, leave it hanging |
| 17 |
NC |
– |
No need to care, leave it hanging |
| 18 |
485-EN |
input /Output |
The enable control pin of the external 485 chip can be left unconnected if it is not used. |
| 19 |
STATE |
output |
Module status indication output, if no floating processing is used |
| 20 |
GND |
input |
Module ground wire |
