What is the difference between serial port and COM port

At present, the interface types of communication equipment include serial port, COM port, UART port, TTL, etc. Today we will take a look at the differences between these interfaces in detail:

　　 1. Serial port and COM port refer to the physical interface form (hardware). And TTL, RS-232, RS-485 refer to the level standard (electrical signal).

　　2. When connecting to the device, generally only connect to GND RX TX. Will not connect to the Vcc or +3.3v power cord to avoid conflict with the power supply on the target device.

　　3, PL2303, CP2102 chips are commonly used USB to TTL serial chip, use USB to expand the serial port (TTL level).

　　4. The MAX232 chip is a dedicated two-way conversion chip for TTL level and RS232 level. It can convert TTL to RS-232 or RS-232 to TTL.

　　5. The TTL standard is that the low level is 0 and the high level is 1 (+5V level). The RS-232 standard is that the positive level is 0 and the negative level is 1 (±15V level).

6. The electrical characteristics of RS-485: Logic "1" is expressed by the voltage difference between the two wires as +(2-6)V; Logic "0" is expressed by the voltage difference between the two wires being -(2-6)V . The interface signal level is lower than RS-232-C, it is not easy to damage the chip of the interface circuit, and the level is compatible with the TTL level, and it is convenient to connect with the TTL circuit.

　　Serial port, COM port

　　 COM port is serial communication port, referred to as serial port. Generally we see two physical standards. D-type 9-pin plug, and 4-pin DuPont header, is a small board from USB to TTL serial port, which can be extended by USB. It is an indispensable tool for embedded engineers who use laptops or desktop computers without COM. In addition to using the serial port to download programs to the MCU, it is also an artifact to assist in debugging programs.