Description
This module allows you to convert serial signal levels (-12, 12V) to TTL levels (0, 5V) into RS485 communications. The RS485 protocol is used in high-speed, long-distance serial communications.
Features:
Based on the MAX485 chip
Half-Duplex Communication
Maximum speed of 10Mbits/s at 12 meters
Maximum length: 1200m to 100kbits/s
 
 
One of the advantages of the RS485 is the long transmission distance. The range depends on the speed, being possible to achieve 35 Mbps in distances less than 10 meters, and up to 100 Kbps in distances up to 1200 meters.
An RS485 bus has two conductors called A and B (inverter). For them, a twisted pair cable is usually used to increase immunity to noise. It is possible to access up to 32, 128 or 254 stations using a single twisted pair.
The protocol works simply by reversing the voltage between A (non-inverter) and B (inverter):
When A+ and B- are considered LOW status.
When A- and B+ are considered HIGH status.
With RS485 we can establish simplex, half-duplex and full-duplex communication. However, for full-duplex communication we will have to establish two different channels, and have a receiver and transmitter in each of the terminals.
RS485 is frequently used in combination with UARTs, to send signals over long distances. It is also common to find it as a physical layer in a Modbus protocol implementation.