COM/CAN接口说明
COM/CAN 接口采用2*4P弹簧端子，COM默认 RS485,可在SF8010中切换 RS232/RS422。
管脚示意图：
SX28管脚定义如下图所示：
| PIN | RS232/CAN | RS485/CAN | RS422/CAN |
| 1 | DCD1 | D1- | TX1- |
| 2 | COM1_GND | COM1_GND | COM1_GND |
| 3 | RXD1 | D1+ | TX1+ |
| 4 | CAN_H | CAN_H | CAN_H |
| 5 | TXD1 | XX | RX1+ |
| 6 | CAN_L | CAN_L | CAN_L |
| 7 | DTR1 | XX | RX1- |
| 8 | CAN_GND | CAN_GND | CAN_GND |
| 9 | DCD2 | D2- | TX2- |
| 10 | COM2_GND | COM2_GND | COM2_GND |
| 11 | RXD2 | D2+ | TX2+ |
| 12 | PWR_SW+ | PWR_SW+ | PWR_SW+ |
| 13 | TXD2 | XX | RX2+ |
| 14 | PWR_SW- | PWR_SW- | PWR_SW- |
| 15 | DTR2 | XX | RX2- |
| 16 | UPS_POK | UPS_POK | UPS_POK |