RS-485 is a kind of multipoint communication, which allows us to “talk with multiple devices” at the same time.
According to the standard, up to 32 devices can be connected at the same time. The maximum distance from end to end is 1200 meters.
However, by using repeaters, the total number of devices and the maximum distance can be expanded.
RS-485 network can be used as two-wire or four wire network.
Four wire network is two-way (two-way calls can be made at the same time), while two wire network can only work in one direction.
It can be a 3-wire or 5-wire system. The third or fifth wire is actually a ground wire.
The disadvantage of RS-485 is that it is more difficult to program because it uses the same two wires to send and receive data. In any given network, only one node can transmit data, and other nodes can only receive data at that particular time. In terms of advantages, it supports long-distance communication without problems. It also uses a lower interface signal level than RS-232, which makes the interface circuit more difficult to damage.