RS485 setup not working

Discussion in 'General Electronics Chat' started by HallMark, Oct 4, 2013.

  1. HallMark

    Thread Starter Member

    Apr 3, 2011
    89
    5
    Hi,

    I am trying to setup RS485 between to microcontroller but any how I was not able to make that so I thought of why not use PC to send and receive data via RS485 so I can check my circuitry.

    Here is my basic setup for RS485.
    [​IMG]

    I have also put 120E resistance between A and B line.

    But I am not able to receive char back on terminal. Is there anything wrong in this setup?
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Are you sure you have your PC/serial port set up correctly? You can try your PC serial port with a simple loopback cable to insure you have everthing working on your PC. Once satisfied with that, you can connect your transceivers and debug them.
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    You've got pins 1 and 4 mixed up.
     
  4. HallMark

    Thread Starter Member

    Apr 3, 2011
    89
    5
    Yes I have done same thing. Loop back on DB9 connector as well as after MAX232 and it was working fine for both MAX232 Chip.
     
  5. HallMark

    Thread Starter Member

    Apr 3, 2011
    89
    5
    Didn't get you !
    Pin 1 and 4 are RO and DI right? I have connected them with MAX232 TTL logic pins.
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Swap pins 1 and 4.
    R1OUT goes to DI.
    T1IN goes to RO.
     
    HallMark likes this.
  7. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    I agree. Mr Chips nailed it.
     
    HallMark likes this.
  8. HallMark

    Thread Starter Member

    Apr 3, 2011
    89
    5
    Thanks MrChips. It is working now.. Thanks a lot.
     
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