Make Your Own Psion Serial Cable

How to make your own Psion 3c/Sienna/s5 serial cable:

The cable is a PCMCIA-type cable assembly connected to a 9 pin D socket. The connections between the pins are identical to those in the PsiWin cable. The D socket cover has thumbscrews to enable secure attachment to a PC, and a strain relief grommet to prolong the life of the cable. The cable is 12 inches long. (I know
that this is a bit short, but the PCMCIA cable assembly only comes with that much cable on it…)

If you want to connect your Psion 3c, s5 or Sienna to a modem rather than to a computer, you will need a null-modem adapter as well.

Construction Details

The parts are available from CPC. Note that the cable assembly is not identical to the connector on the cable that Psion supply, having a different arrangement of small plastic keyways. This doesn’t usually makes any difference in practice.

Part Number:      Description:

CN00842           PCMCIA Cable Assy
CSSOCKET15        9 way socket (pack of 10)
CNDPT9B           Plastic D hood and thumbscrews
CSCPL-12          D hood black cable grommet (pack of 10)

Connections for Psion 3c / Sienna serial cable are:

 Psion:
    _____________
 1  \___________/  15

 9-pin D socket:
   ---------------
   \  5 4 3 2 1  /
    \  9 8 7 6  /
      ---------

9-pin:  Psion:  RS232:
1       nc      DCD     data carrier detect
2       4       RD      received data
3       8       TD      transmitted data
4       5       DTR     data terminal ready
5       15      SG      signal ground
6       3       DSR     data set ready
7       7       RTS     request to send (= DTE ready)
8       2       CTS     clear to send (= DCE ready)
9       6       RI      ring indicator
Last modified: 9 August 2009

3 thoughts on “Make Your Own Psion Serial Cable

  1. Dear Nathan:
    Many thanks for this fascinating and useful advice. I would also be grateful for your advice on the following problem. All my computers have 15-pin serial connectors rather than 9-pin or 25-pin connectors. If I were to make a cable to link the Psion 5mx to a laptop, would it be okay simply to use your 9-pin pinout in a 15-pin plug housing? Or would I be likely to run into difficulties with this? I already have an unfinished Psion cable which I could wire-up for this purpose. Thanks for your valued help.

  2. Are you sure it is serial? I’ve never seen a 15 pin serial before, 15 pin connectors are usually VGA (3 rows of 5 pins) or on very old computers a 15 pin with a row of 8 and a row of 7 pins was used as a joystick port or AUI ethernet.

    If it is definitely RS232 it would work but you would need to find out which pin is which as it is unlikely to use the same pins numbers as the 9 pin.

  3. Thanks for this, Nathan.
    In view of the rarity [or non-existence!) of 15-pin serial connectors which you indicate, I’m now pretty sure the connectors I described are actually VGA. I’ll have to experiment with 9-pin / USB connectors instead.
    One further problem I’d appreciate your advice on. I’ve got an incomplete Psion 5mx cable with a completed Psion end. I’d like to complete the cable by soldering the other end to a RS232 9-pin male connector. Most of the wiring looks straightforward, including the signal ground wire — but what do I do with the cable ground (the bare wire)? Its connection (if any) doesn’t appear in any diagram I’ve consulted. Is the non-Psion end simply left as a free-floating wire? Best regards and thanks!

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