COM/CAN接口说明
COM/CAN接口采用2*4P弹簧端子，可选择配置RS232/RS485/RS422。
管脚示意图：
SX51管脚定义如下图所示：
| 管脚 | RS232/CAN | RS422/CAN | RS485/CAN |
| 1 | DCD | TX- | DATA- |
| 2 | COM_GND | COM_GND | COM_GND |
| 3 | RXD | TX+ | DATA+ |
| 4 | CAN_1_H | CAN_1_H | CAN_1_H |
| 5 | TXD | RX+ | - |
| 6 | CAN_1_L | CAN_1_L | CAN_1_L |
| 7 | DTR | RX- | - |
| 8 | CAN_GND | CAN_GND | CAN_GND |