1. The physical structure of the interface is different
The RS232 interface comes in the form of 9 pins (DB-9) or 25 pins (DB-25), and there are two sets of RS232 interfaces on general personal computers, called COM1 and COM2. The RS485 interface does not have a specific physical shape and is used according to the actual situation of the project.
2, interface electronic characteristics are different
The signal level of RS232 interface is high, which is easy to damage the chip of the interface circuit. The voltage of any signal line on the RS232 interface is negative logic. That is, logic \"1\" is -3 to -15V, logic \"0\" is 3 to 15V, and the noise tolerance is 2V. That is, the receiver is required to recognize a signal higher than 3V as a logical \"0\
The logic 1 of the RS485 port is expressed as the voltage difference between two wires between 2V and 6V, and the logic 0 is expressed as the voltage difference between two wires between -6V and -2V. The interface signal level is lower than RS-232-C, it is not easy to damage the interface circuit chip, and the level is compatible with TTL level, and it is convenient to connect with TTL circuit.
3, the length of communication distance is different
RS232 transmission distance is limited, the maximum transmission distance standard value is 15 meters, and only point-to-point communication, the maximum transmission rate is up to 20kB\/s.
The maximum wireless transmission distance of RS485 is 1200 meters. The maximum transmission rate is 10Mbps, and the maximum communication distance can be achieved at the transmission rate of 100Kb\/S.