People can use serial to Ethernet module to realize the serial to Ethernet functions. It is very convenient for people to use. But there are some new problems need to mention: Serial to Ethernet is not the conversion of transmission media, but the protocol conversion of serial to TCP/IP.

 

 

Generally, a serial port is a UART, which actually defines only the specification of the data link layer, namely the start bit, data bit and stop bit. However, in the different physical layer, it is divided into TTL serial port, RS232 serial port, RS485 serial port, etc.

TTL serial port: it is a serial port for data communication between MCU chips. It takes +5V (or + 3.3v) to represent 1 and GND to represent 0.

 

RS232 serial port: RS232 serial port is a serial port which can realize communication between different devices. It mainly changes the signal voltage from 0 ~ 5V to ±15V (generally ±12V in practice). The increase in voltage increases the distance and reliability of data transmission.

 

RS485 serial port: RS485 serial port is a serial port which can realize long-distance communication, the maximum transmission of RS485 serial port is 1000 meters. The main feature of RS485 serial port is to replace RS232 common-mode signal (voltage between the signal line and GND) with differential mode signal (voltage between A and B lines), so as to resist common-mode interference and realize long-distance transmission.

 

According to the 7 layer model of ISO (physical layer, data link layer, network layer, transport layer, session layer, presentation layer, application layer), serial ports actually only include physical layer and data link layer. While TCP/IP protocol should belong to the network layer and transport layer. So serial TCP/IP is not accurate. Ethernet belongs to the physical layer and data link layer, so serial to Ethernet is more accurate.

 

Since most protocols running over Ethernet are TCP IP protocols, serial to Ethernet can also be called serial port to TCP IP.