Clarify one concept： whether serial to Ethernet or serial to TCP/IP？
Generally speaking, the serial port is generally a UART, which actually only defines the specification of the data link layer, that is, the start bit, the data bit, and the stop bit. However in different physical layers, it is divided into: TTL serial port, RS232 serial port, RS485 serial port and so on.
TTL serial port: It is a serial port for data communication between MCU chips, +5V (or +3.3V) represents 1 and GND represents 0.
RS232 serial port: It is a serial port for communication between devices, which mainly changes the signal voltage from 0～5V to ±15V (actually ±12V). The increase of voltage increases data transmission distance and reliability.
RS485 serial port: It is a serial port for long-distance communication, which can realize data transmission of up to kilometer. Its main feature is to replace the RS232 common mode signal (the voltage between the signal line and GND) with the different-mode signal (the voltage between the two lines A and B), so as to resist common mode interference and achieve longer distance transmission.
If it is divided according to seven-layer model of ISO (physical layer, data link layer, network layer, transmission layer, session layer, presentation layer, application layer), the serial port actually only contains the physical layer and the data link layer. TCP/IP protocols shall belong to network layer and transmission layer. Therefore, serial to TCP/IP is not correct. Ethernet belongs to the physical layer and data link layer, so serial to Ethernet is more accurate.
Since most of the protocols currently running on Ethernet are TCP IP protocols, serial to Ethernet can also be said to be serial to TCP IP.