Psion PDAs use serial ports, which are rare on modern PCs. If you are not able to add an internal serial port, and don't have an old PC (with a suitably-old distribution of Linux that runs on the hardware and has
plptools), then you could use a USB-to-Serial converter.
If using a USB-to-Serial converter, you might find
plptools does not fully work on recent Linux kernels/distributions (see below re Debian bug #601612), and problems may also occur if you try to compile it on a Mac. So here's a way to set it up in an older distribution running in VirtualBox.
I got it to work in VirtualBox with Debian 3.1 Sarge and its 0.12 plptools package:
http://archive.debian.org/debian sarge main(unless you have a full CD set), and apt-get install plptools
-s /dev/ttyUSB0(leave plpnfsd and plpprintd off; it seems more robust to just use plpftp)
sshfsto access its filesystem from the real machine):
sshfs -o IdentityFile=/path/to/keyfile -o sshfs_sync -o port=8022 localhost: $HOME/sarge
ssh -i /path/to/keyfile -p 8022 localhost
savestatecommands, but make sure to unmount the sshfs before hibernating the virtual machine (especially if you're on a Mac---some versions of Mac FUSE can crash the kernel if you try to access a mount whose virtual machine has stopped). Some delay might be needed after the
startvm, especially if the state has not been saved.
It did not work for me to run Sarge chroot or forward-port its version of plptools, so it seems the kernel is part of the issue. (Debian bug #601612 reported a forward-port working with a QinHeng adapter but I couldn't do it with a Prolific.) It is therefore necessary to run a whole virtual machine if you need to connect a Psion to a modern computer, but at least by modern virtual machine standards it's a lightweight one.
I was not able to measure the connector exactly, but it fits one that's specified as:
The Revo's specs say 500mA 6V DC +/- 10% so 5.4-6.6V. Some companies marketted 4*AA "external battery packs" but these required alkalines (4 AA NiCd or NiMH rechargeables are likely to produce only 4.8V; NiZns are within the specs but need a special charger, otherwise you'd need 5*1.2V with suitable holder and a charger that can take an odd number of batteries). A Revo might accept 4.8V for running but not charging, but this isn't in the specs and I don't know if it varies from unit to unit.
The 5mx/MC218 is more likely to have screen problems than battery problems (the 5's screen cable was better than the 5mx's although still not brilliant; some people fit replacement cables from 'flexi' etc; not sure about the Oregon Osaris but it ran EPOC 4 so I don't know if it would work with Macro5 and keybLayout).