RS232 to RS485 Converter, RTS controlled

This project demonstrates designing an electronic project using the Protel Autotrax PCB CAD package. The project starts with an empty circuit sheet and shows the selection and addition of components. There is a way of using RS232 to RS485 converter "blank components" as drawing numbers that is illustrated on the following page - it ties together circuit, PCB and Bill of Materials. The sequence builds on the circuit, and goes through basic concepts such as connections, nets, labelling, moving pins. The page shows how to make a netlist, and then how the netlist appears in the PCB package to guide the PCB layout. The steps to laying out the PCB are shown after that. The tutorial is made all the more realistic as there is a fault discovered later that is then repaired - which happens all the time with real prototypes.

The project designed in the tutorial is an RS232 to RS485 converter. This is a often needed device which can demonstrate a lot of principles of circuit design, and will be useful for some applications as a finished unit. Without meaning to confuse the issue, there is also have available a second, more up-to-date 232-to-485 converter. To see just the example version of the RS485 converter without the tutorial, click here.

Other Projects: Library

RS232 to RS485 Converter specification

  • DE9 RS232 connector compatible with PC
  • TxD and RxD translated from RS232 to RS485
  • Direction of transmission controlled by PC RTS line
  • Handshake loop the PC connection so it works with all software
  • RS485 signals output on 6 way modular jack
  • Indicator LED(s) to show communications traffic
  • Power supplied by external unregulated 9v plugpack
  • ... and a few extra features, not essential, but desirable
    • RS485 Termination resistor, jumper selectable
    • Pullup/Pulldown resistors on RS485 to establish line-idle condition

Select one of the Links below to go to the RS485 converter or the tutorial.

Tutorial RS485 converter without the tutorial