The difference between rs485 and rs232
1. Physical aspects of the interface
RS232: The RS232 interface connector uses a 25-pin socket with model DB-25. The RS-232 interface of some devices connected to the PC, because it does not use the other party's transmission control signal, only needs three interface lines, namely "send data", "receive data" and "signal ground". Therefore, DB-9 is used. The core plug socket, the transmission line adopts shielded twisted pair.
RS485: RS485 has no specific physical shape, and is an interface adopted according to the actual situation of the project.
2. Electrical characteristics of the interface
RS232: The signal level value of the transmission level signal interface is relatively high (signal "1" is "-3V to -15V", signal "0" is "3 to 15V"), which is easy to damage the chip of the interface circuit, and because it is related to the The TTL level (0~"<0.8V", 1~">>2.0V") is not compatible, so it is necessary to use a level conversion circuit to connect with the TTL circuit. Poor anti-interference ability.
RS485; Transmission differential signal logic "1" is represented by the voltage difference between the two lines as + (2-6) V; logic "0" is represented by the voltage difference between the two lines as - (2-6) V. The interface signal level is lower than that of RS-232, so it is not easy to damage the chip of the interface circuit, and the level is compatible with the TTL level, which can be easily connected with the TTL circuit. Strong anti-interference ability.
3. The length of the communication distance
RS232 transmission distance is limited, the maximum transmission distance standard value is 15 meters, in fact, it can only be used in about 25 meters.
The standard value of the maximum transmission distance of RS485 is 120 meters, but it can actually reach 3000 meters.
4. Can it support multipoint communication?
The RS232 interface allows only one transceiver to be connected to the bus, and cannot support multi-station transceiver capabilities.
The RS485 interface allows up to 128 transceivers to be connected on the bus. That is, it has the ability of multi-station communication, so that users can use a single RS485 interface to easily establish a device network.
5. Differences in communication lines
RS232 can use three-core twisted pair, three-core shielded cable, etc.
RS485 can use two-core twisted pair, two-core shielded cable, etc.
6. Maximum baud rate for transmitted data
The transmission rate of RS232 is low, and the maximum baud rate is 19200bps. Although the transmission speed is very slow, it is still very practical in many occasions.
The maximum data transmission rate of RS485 is 10Mbps. The transfer speed is much faster!
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