Bidirectional communication from RS-232 to half-duplex RS-485 using arduino nano

Projects Networking, Protocols, and Devices
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You can use a CD74HCT126 or 125 or SN74HCT126 or 125 to do the switching.
You will need 3 control signals, two for the 125/126 part and one for the RS485 driver.
You can also disconnect everything using this set-up so you can download code to the Arduino.