A serial port, abbreviated as “serial port”, is an expansion interface that uses serial communication. Data is transmitted bit by bit. This interface was standardized by the Electronic Industries Association of the United States in collaboration with institutions such as Bell System in 1970. Common types include RS-232-C, RS-422, and RS-485. Its communication lines are simple, requiring only a pair of transmission lines to achieve bidirectional communication. It is suitable for long-distance transmission but has a relatively slow speed, with typical rates ranging from 20kb/s to 10Mb/s. On PCs, it is usually referred to as the COM port. Data transmission is carried out using the transmit (TX), receive (RX), and ground (GND) pins. Modern computers can connect devices that rely on communication ports through USB serial adapters [7-8]. Virtual serial ports are presented in the operating system through USB drivers and support traditional device communication [7].
RS-232-C uses single-ended communication and has a maximum transmission distance of approximately 15 meters and a maximum speed of 20kb/s. RS-422 and RS-485 use balanced transmission and support multi-point communication. The maximum transmission distance is up to 1219 meters and the maximum speed is 10Mb/s. USB is a universal serial bus with a transmission rate of up to 480Mbps and supports hot plugging and multiple device connections. High-speed serial port communication rates have developed up to 56Gbps or even 112Gbps, using through-hole manufacturing and gold plating processes to break through physical limitations [10]. The serial port protocol layer includes start bit, data bit, parity bit, and stop bit, and both parties need to agree on parameters such as baud rate and data format. It is mainly used in industrial automation, embedded system debugging, and traditional device communication. Serial port servers use protocol conversion to connect IoT devices with cloud platforms, enabling device networking rates of up to 95% in smart park projects [5-6] [11]. The PCI serial port card market covers types such as 2-port and 4-port, and is used in industrial and commercial fields [9].