Differences Between RS485 2W and RS485 4W Touchscreen Serial Interfaces
We see that this touchscreen serial interface has RS485 as well as RS232. Here, we will briefly explain and distinguish between the serial interfaces RS485/RS232/RS422.RS232:Is a three-wire communication (1 transmitting wire, 1 receiving wire, and 1 common wire which is the reference ground GND).RS422:Is a four-wire communication (1 for transmitting +, 1 for transmitting -, 1 for receiving +, and 1 for receiving -).RS485:Is a two-wire communication (1 for positive signal and 1 for negative signal).From the above, we can see that RS422 connects the two positives together and the two negatives together, thus forming RS485.First, let’s look at the pin definition diagram for the serial port (the definition may vary for different models of touchscreen). RS-485 4W uses four wires: 1 is Rx-, 2 is Rx+, 3 is Tx-, and 4 is Tx+. RS-485 2W uses two wires: 1 is Data-, and 2 is Data+. Are the wires for RS-485 4W and RS422 actually the same? They are both four wires. In fact, RS-485 4W can be said to be RS422, which is full duplex, while RS-485 2W is half duplex.So what is the difference between full duplex and half duplex?Full Duplex:Can be simply understood as a communication system where each end is equipped with a transmitter and a receiver, allowing both parties to send and receive data simultaneously without needing to switch directions.Half Duplex:Uses one wire for both sending and receiving. Although data can be transmitted in both directions, the two parties cannot send and receive data simultaneously, thus requiring a switch to toggle between receive/send.To summarize, RS485 2W indicates a wiring method, which is a two-wire system, meaning there are two signal wires to connect besides GND, and it is a half duplex communication method. RS485 4W indicates a wiring method, which is a four-wire system, meaning there are four signal wires to connect besides GND, and it is a full duplex communication method. Now you can remember this! (Original by Cai Huixing from Jicheng Training, unauthorized reproduction is prohibited, violators will be prosecuted!)
