RJ45 to RS232

Discussion in 'Cisco' started by Fred Atkinson, Mar 5, 2006.

  1. I need to put together an adapter that will take the DCE end
    of a rollover cable and allow me to connect to a DB25, RS232, DCE type

    I've made a drawing for it that can be viewed at

    I'd appreciate any feedback on it. Jameco has the adapter but
    you have to set the pins yourself. That's why I need the drawing.


    Fred Atkinson, Mar 5, 2006
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  2. I've revised the drawing showing the proper color code for the
    pinout in the RJ45/RS232 adapter. However, I've put this adapter
    together accordingly and connected it to a Cisco rollover cable and
    plugged it into a DCE type device (that I am confident is working).

    I'm not getting any data from the unit. I've checked my
    settings and it seems to be right.

    You can take another look at the pinout at
    http://paws.wcu.edu/fatkinson/APRS/RS232_RJ45.pdf. Does anyone see
    any problems with it?


    Fred Atkinson
    Fred Atkinson, Mar 13, 2006
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  3. Fred Atkinson

    Merv Guest

    Just curious what are the devices at each of this specil cable ?
    Merv, Mar 13, 2006
  4. Fred Atkinson

    Merv Guest

    Are you trying to build the equivalent of a Cisco
    RJ-45-to-DB-25 male DCE adapter (labeled "MODEM") CAB-25AS-MMOD

    RJ-45 Pins MMOD Pins
    1 5
    2 8
    3 3
    4 7
    5 7
    6 2
    7 20
    8 4
    Merv, Mar 13, 2006

  5. That did it. I tested the leads that way and they work.

    The only problem is that both pins four and five are supposed
    to plug into pin 7 on the DB25. That is not easily doable without
    some soldering or something.

    Do you think I might be able to find another pin for a ground?
    Regards, and my thanks,

    Fred Atkinson, Mar 14, 2006
  6. Fred Atkinson

    Merv Guest

    I see CAB-25AS-MMOD for sale on ebay and from a number of suppliers if
    you are not able to find an extra pin
    Merv, Mar 14, 2006
  7. That's not what I meant. I meant a pin on the DCE unit that
    carried a ground.

    No matter. I've got it working.

    Regards, and thanks.

    Fred Atkinson
    Fred Atkinson, Mar 17, 2006
  8. Fred Atkinson


    Jan 5, 2012
    Likes Received:
    The Fix

    I used just one of the grounds for my console cables I made up..... they are "usually bridged signal grounds". What was your fix, and can you post pin-out used ?

    Eric Peyser
    erixnow, Jan 5, 2012
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