1. Introduction to rs485
RS485 is a standard that defines the electrical characteristics of drivers and receivers in a balanced digital multipoint system. The standard is defined by the Telecommunications Industry Association and the Electronics Industry Alliance. Digital communication networks using this standard can effectively transmit signals under long-distance conditions and in environments with high electronic noise. RS-485 makes it possible to configure cheap local networks and multi-branch communication links.
RS485 has two-wire and four-wire connections. The four-wire system can only achieve point-to-point communication. It is rarely used now. Nowadays, the two-wire connection method is mostly used. This wiring method is a bus topology. Up to 32 nodes can be connected on the same bus.
2. Introduction to rs232
RS232 interface is a standard for serial communication jointly developed by the Electronic Industries Association (EIA) of the United States in 1970 in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers. Its full name is "Technical Standard for Serial Binary Data Exchange Interface Between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)".
The standard stipulates that a 25-pin DB25 connector is used, and the signal content of each pin of the connector is specified, and the level of various signals is specified. So the question is what is the difference between rs485 and rs232? Take a look.
3. The difference between rs485 and rs232
1) Physical performance aspects of the interface
RS232: The RS232 interface connector uses a 25-pin plug socket with a model of DB-25. The RS-232 interface of some devices connected to the PC, because they do not use the other party’s transmission control signal, only three interface lines, namely "send data", "receive 66 data" and "signal ground". So use DB-9 The core plug seat, 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 high (signal "1" is "-3V to -15V", signal "0" is "3 to 15V"), it is easy to damage the chip of the interface circuit, and because of the TTL level (0~""0.8V", 1~""2.0V") is not compatible, so you need 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 wires as + (2-6) V; logic "0" is represented by the voltage difference between the two wires as-(2-6) V. The interface signal level is lower than RS-232, 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. 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 at about 25 meters.
The standard value of RS485 maximum transmission distance is 120 meters, which can actually reach 3000 meters.
4) Can it support multi-point communication?
The RS232 interface only allows 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 multi-station communication capability, 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 wire, etc.
RS485 can use two-core twisted pair, two-core shielded wire, etc.
6) The maximum baud rate of transmitted data
RS232 transmission rate is low, the highest baud rate is 19200bps. Although the transmission speed is very slow, it is still very practical in many occasions.
The highest data transmission rate of RS485 is 10Mbps. The transmission speed is much faster!
Our other product:
