I have an old Psion II LZ handheld and a crazy idea to use this as a remote to control my home automation.
This involves creating an bluetooth adapter for the Psion and connecting via bluetooth to a RPI running the home automation software.
Once, I had the CommLink software installed, the next step was to build the hardware. For this, I again turned to Jaap's site and the schematics drawn by Olivier Gossuin.
(I'm not sure that the schematics are 100% accurate, but they where enough to help me build my own Comms Link)
Since I had the software in a DataPak in slot C, I wasn't sure if it would work with the hardware in the top slot. Only one way to find out - build it and see.
So I built a simple interface using just 2 ICs; a 74HC244 and a 74LS00 (I didnt have a 4011 to hand). I only connected RX and TX (no handshaking signals) and connected them to a USB to serial converter.
It worked! I could communicate between my PC and the Psion at 9600 baud over serial.
I bought the Psion and a number of blank 32K DataPaks. I have no Comms Link so no means to get any data onto the Psion (other than typing it in).
So, the first task was to build a DataPak reader/writer.
Jaap's excellent website https://www.jaapsch.net/psion/ has all the information I needed to build a DataPak reader/writer. Using an adruino pro micro. This uses 8 pins as a data bus, 5 pins for control (RESET, CLOCK, OUTPUT ENABLE, SLOT SELECT and PROGRAM) and one to generate the programming voltage via a boost converter.
With this, I was able to program the CommsLink 4.2 software into a blank DataPak.