The Psions have both serial and infra red ports. Either can be used for connectivity, but most connectivity programs currently only have features for the serial port connection.
Armin Podtschaske x-rayed the "honda" connector. His page has an explanation of the pin out in German.
Here it is for those who don't speak German :).
Pin 1 is on the top and pin 15 is on the bottom. Only pins 2 through 8 and 15 are connected.
See the IrDA HOWTO for information about using the Linux IrDA driver with a Psion. It is possible to beam files from Psion 5 (mx) via Linux-IrDA to a Linux System. The irda-utils include a special client psion5.c which can beam files between them.
There are two builtin software methods to use the communications ports. The first is the remote link, <ctrl>-l from the main file menu, which can be set to serial, infrared or off.
EPOC also provides the program comms. The remote link must be set to off for the comms program to have access to the serial port.
plptools (current releases from Matt Gumbley) was originally developed by Fritz Elfert, who had merged plp and p3nfs/p5nfs. plptools is currently being worked on by members of the Linux-Psion mailing list.
plptools comprises of 3 different programs. ncpd provides a socket connection to the Psion. plpnfsd provides mounted filesystem access to the Psion and plpftp provides ftp access to the Psion.
See ftp://ftp.to.com/pub/psion/ for Fritz' original releases.
ncpd [-V] [-v logclass] [-d] [-p <port>] [-s <device>] [-b <baudrate>]
plpnfsd [-v] [-V] [-p port] [-d mountdir] [-u user]
First start ncpd get it to listen on a port (7501 by default) for connection requests. Then, start either plpnfsd or plpftp. plpnfsd defaults to mount the Psion under /mnt/psion.
kpsion is available under unstable/apps/utils/ at your favorite KDE mirror.
It provides a method to use kfm (KDE File Manager) to directly access files on the Psion via a serial link. Psion files can be opened by using 'psion:' or 'epoc:' URLs. It uses ncpd from the plptools package, which must be running to use kpsion, to handle the serial connection.
kpsion also has a Psion Word->HTML/Text viewer/ converter built from psiconv to allow viewing documentation created with Psion Word under Linux.
kpsion is currently ALPHA support for connecting to a Psion Series 5*. It is only available in source and only builds against KDE 1.1 and KDE 1.2. Please read the README and INSTALL files that come with the tarball.
p3nfs mounts the psion drives over the serial cable at /psion.stand/mnt, by default.
Matt Gumbley originally started ncp for use with his Psion Series 3. Now that he's working on plptools, you should use that :). However, ncp might still be of interest to users of a Psion Series 3, which this HOWTO doesn't cover :). Matt's ncp page also has information about the plp protocol.
Psiconv translates Psion Word documents to HTML (3.2 or 4.0) or plain text.
The EPOC SDK works on Linux via WINE, see Olaf Flebbe's web page for instructions on how to get it working.
hermes is a fully featured vt100 emulator.
Olaf Flebbe has perl running under EPOC.
Duncan Booth has python running under EPOC.
E_Shell is a DOS-like shell environment. It provides ways to launch programs from a command line; to check for file system corruption; to create, edit and display plain text files; to check on currently active processes and threads.
c2f converts the Psion contact file to a comma delimited format.