Microcontroller interface using RS485 & RS422
After a period of research, I found out that RS485 and RS422 is in fact the same.
RS422 is a duplex configuration. RS422 using 4 wire to communicate in both direction. One pair of wire to do transmit and the other pair to receive. Both sides is able to transmit and receive at the same time.
RS485 is a half duplex configuration. RS485 using only 2 wire to communicate in both direction. With only two wire, it means that when one side is transmitting, the other side of the communication line will be receiving. Both side cannot be transmitting at the same time. For RS485 transceiver, use MAX485 or MAX3485. They have the same pin out except that MAX485 uses 5V supply, MAX3485 uses 3.3V supply.
RS422 can be connected to work with RS485 to either receive or transmit date, but not both. RS422 can be wired directly using a pair of wire, +ve to +ve, -ve to -ve terminal. For RS422 transceiver, use MAX488 or MAX3488. They have the same pin out except that MAX488 uses 5V supply, MAX3488 uses 3.3V supply.