RS232-to-RS485 Converter

June 08, 2008 | 0 Minute Read

Since my Ifos project relies on Modbus over RS485, I needed a simple way to interface to an RS485 network from my PC during development.

Here’s a simple single-chip converter based on the MAX3162. A DB-9F connects to the serial port on the PC, while the RS485 bus is accessed via an RJ-45 connector.

I didn’t implement any hardware flow control, for simplicity, but the chip certainly supports it. This circuit includes bias resistors on the RS485 balanced RX pair (which is appropriate to my situation). It also provides power to the RS485 bus at any old desired voltage, with a tap through a linear regulator to drive the converter chip at +5V.