RS485 Communication
RS 232 was born earlier before RS 485. But it has deficiencies.
1. The signal level of the interface is relatively high, reaching more than ten V, which is easy to damage the chip of the interface circuit, and is not compatible with the TTL level, so a conversion circuit must be added if it is connected with the single-chip circuit.
2. The signal line used by the interface forms communication in the common ground mode with other devices. This common ground mode transmission is prone to interference, and the anti-interference performance is relatively weak.
3. The transmission distance and speed are limited, and the communication can only be performed at a maximum of several tens of meters; the communication can only be performed between two points, and the multi-machine networking communication cannot be realized.
In view of the shortcomings of the RS232 interface, new interface standards such as RS485 have emerged. RS485 has the following characteristics:
a. 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 RS232, which is not easy to damage the chip of the circuit, and the level is compatible with the TTL level, which can be easily connected to the TTL circuit
b. RS485 communication speed is fast, and the maximum data transmission rate is more than 10Mbps; its internal physical structure adopts a combination of balanced driver and check-point receiver, which greatly increases the anti-interference ability.
c. The longest transmission distance can reach about 1200 meters, but the transmission rate and transmission distance are inversely proportional. Only the transmission rate below 100KB/s can achieve the maximum communication distance. If you need to transmit longer distances, you can use relays.
d. Multi-machine communication can be realized by networking on the bus, and multiple transceivers can be hung on the bus. From the perspective of the existing RS485 chip, there are drivers that can connect different devices such as 32, 64, 128, and 256.
We have the smart electric meter with RS485 communication. Such as wifi energy meter and Lora wan electric meter. For more information, please feel free to contact us.
