Psion 3 Communication Notes

The best miniature computers on the planet

Communicating with other computers, printers, from Psion 3.

Psion 3c/Siena via Infrared to Windows 95

Full instructions on connecting to a Dell laptop by Phil Spencer at

Basically you fool the Psion 3c into handling the IR port like a serial port. From the System screen, open Communication, and set Use to Link Cable, baud rate 19,200 (you can try higher or lower later), then move down the Communication screen to Extra Parameters, and add -sTTY:I and press Enter. The link zigzag should appear in the right hand status window.

On the PC, from PsiWin, load Psion Manager, don't try to connect. In Psion Manager, Setup, set Communications to use the COM: port associated with your IrDA port (probably COM: 3 or COM: 4). OK, and exit Psion Manager, and restart it. Watch connection box, and keep clicking retry (takes a while sometimes). Don't forget to turn off the communications afterwards in the Psion, to preserve your batteries.

Psion InfraRed Communications Software

Jim Pollock's site has a nice range for Psion 3c, Siena and Series 5. Irbackup and Irestore backup from 3c and Siena to PC. Adds two 5k OPA files to Psion (the zipped files are 35k). Pdir is used with IrCopy and shows your Psion files on PC display. IrCopy copies between PC and 3c or Siena. Uses irNFS server on Psion. IrSave runs under DOS on your PC, and lets the PC mimic Psion IR protocol. Psion 3c or Siena think PC is another Psion. IrSend supports Psion 5, 3c and Siena, runs on PC only, detects which Psion is beaming. Jim also lists a couple of simple OPL programs for 3c and Siena so you can start experimenting with IR. IrDumpr dumps raw IR bytes to display. IrDump dumps IrDA frames to display.

PsiMail FAQ

Jochen Siegenthaler has an unofficial but helpful PsiMail (for Psion 3c and Siena) FAQ and bug list formerly at It lists how to install an minimum subset of PsiMail, connections for a GSM mobile phone, cable connections. He gives advice on handshake (Xon/Xoff off, RTS/CTS on, DTR/DSR on, usually DCD off), and init strings (AT F - factory default).


A VT100/ANSI terminal emulator for the Psion 3/3c 80x24 display as well, and directions to modem connection information. Serge Shestopalov

Psion 3c Modem Cable

The PsiWin cable with your Psion 3c (and 5) is a null modem cable, so you need a null modem converter to convert it to a "straight through" cable for a modem. If your modem has a 25 pin connector, modify a 9 pin to 25 pin adaptor.

Here is a 9 pin to 25 pin adaptor, as supplied,

Signal                  9pin   25pin (Psion Honda)
Carrier Detect          1       8
Receive Data            2       3       4
Transmit Data           3       2       8
Data Terminal Ready     4      20       5
System Ground           5       7      15
Data Set Ready          6       6       3
Request to Send         7       4       7
Clear to Send           8       5       2
Ring Indicator          9      22       6

Your standard 25 pin null adaptor wires pin 7 straight through, swaps 2 and 3, 4 and 5, 6 and 20.

So here is the 9 pin to 25 pin null modem adaptor.

Signal                  9pinM  25pinM   Cross wiring on 9 pin connector
Carrier Detect          1*      8       (Pin 1 sometimes linked to 6)
Receive Data            2  in  2
Transmit Data           3  out  3
Data Terminal Ready     4  out  6*      (Pin 6 sometimes linked to 8)
System Ground           5  ---  7
Data Set Ready          6* in 20       (Pin 6 sometimes linked to 1)
Request to Send         7  out  5
Clear to Send           8  in  4
Ring Indicator          9      22       (Psion connect 9 RI to 8 DCD)

I think Psion are wrong in not connecting their Pin 1 (on 9 pin D connector) Carrier Detect to the modem. Go to the Psion Control panel, select Modems, switch to Advanced Tab and Disable Carrier Detect (DCD).

Otto Sykora in Switzerland lists his home made 9 pin Null Modem cable, intended for the Revo.

9-1 (not essential)

I couldn't find a 9 pin null modem adaptor, so I looked for a DB9 Male to DB9 Male gender changer adaptor, with a removeable cover (most have one piece covers). Tandy (Radio Shack) had their 260-0280 model with clip together sides. So I just rewired it.

Psion 3mx Honda connector

If you hold your 3mx so the side with the RS-232 connector is facing you= then from right to left (the rightmost pin is 1, across to pin 15 on the= left):

Pin  1: Siena=3DVin(6VDC) or 3c/3mx=3D5V out (30mA max) (3a SIBO Pin 3)=
Pin  2: RS-232 RTS out
Pin  3: RS-232 DTR out
Pin  4: RS-232 TxD out
Pin  5: RS-232 DSR in
Pin  6: RS-232 DCD in
Pin  7: RS-232 CTS in
Pin  8: RS-232 RxD in
Pin  9: SIBO data direction control
Pin 10: SIBO active low peripheral detect
Pin 11: SIBO external switch on (3a SIBO Pin 6)
Pin 12: SIBO peripheral interrupt (3a SIBO Pin 5)
Pin 13: SIBO serial data (3a SIBO Pin 1)
Pin 14: SIBO data clock (3a SIBO Pin 2)
Pin 15: signal and power ground (3a SIBO Pin 4)

3a SIBO connector, seen from side (key notch at bottom):
2 4 6
1 3 5

The 3a can detect when the 3link is plugged in, so I guess Pin 10 above does a similar job. I don't know how Pin 9 relates to the 3a connector. Note that Psion describe the SIBO channel as for test only, using 3v logic levels. The Siena SSD adaptor uses these pins, so they do work, and I think I've heard that the SSD adaptor also works with 3c/3mx machines (drive C). The problem is that the 3a uses 5v logic levels and all the peripherals would require 5v, while the Siena SSD adaptor can operate on 3v. So you would also need some sort of level convertor.

Justin Buckland had a site with lots of Psion connectors listed at Phil Whiles has a list of what Psion told him about cables at

This site will look much better in a browser that supports W3C web standards but it is accessible to any browser or internet device, including Psion Web and similar PDA or limited browsers. Netscape 4.x users - turn Style Sheets off. Your style sheet support is too broken to use (sorry). -> epoc -> communications -> sibo-comms

Contact Webmaster PO Box 640, Airlie Beach, Qld 4802 Australia