RS485 half duplex communication

Thread Starter


Joined Apr 1, 2022
I am using half duplex RS485 transceiver adm2483 for communication with pic controller at UART which is full duplex and i am getting synchronization error i am able to transmit the string but i m not getting response from other device through RS485 .please help

Andrei Suditu

Joined Jul 27, 2016
Looking at your RS485 IC datasheet it has 2 separate control pins to enable/disable the driver/receiver.

To transmit you need to enable the driver first and you probably want to disable the receiver if you are not interested in looping back what you sent.

The other endpoint(RX endpoint) needs to disable it's driver beforehand and enable it's receiver.

You can't transmit and receive simultaneously and you need to think of a protocol scheme to prevent transmitting at the same time from both endpoints.

This depends on your application ,but it's OK to consider 1 device a master and the slaves should transmit back/replay only when asked before hand and master gave them permission to drive the bus.

Also the application note says something about power good pin/internal circuitry since your driver is isolated.

Draft up a protocol communication scheme in EXCEL/Visio and that should help.