Remember the Psion Organiser? If you do, chances are you were an early adopter, as the 8-bit pocket computer had its heyday in the mid-1980s. Things have come a long way since then, of course, but just how far is illustrated nicely by the fact that a Raspberry Pi Pico can stand in for the Psion’s original memory packs.
Like many of the early attempts at putting a computer in your pocket, the Psion II had removable modules, which were dubbed “Datapaks”. The earliest versions of the Datapaks were little more than an EPROM chip on a small PCB, and the technical limitations of the day plus the quirky way of addressing the memory made it possible for [Amen] to mimic a Datapak using a modern microcontroller.
The first version was a breakout board that extended out of the Datapak slot significantly, with a Pico, OLED display, SD card slot, and a bunch of pushbuttons. That prototype proved that the Pico was indeed fast enough to fool the Psion into thinking a legit Datapak was plugged in. [Amen] later refined the design by making a board that stuffs everything into the Datapak slot, with the exception of the OLED which still dangles out where it can be seen. He puts the faux memory to the test in the video below.
It’s great to see groundbreaking tech of yesteryear like the Psion being taken care of and returned to use. We’ve seen others try before; here’s a hack that uses a Pi to connect a Psion Organiser to the internet through its RS-232 serial port.
This is awfully cool. I wonder what other old computers are in range?
I was initially thinking this a similar protocol to what Atari’s Lynx used, but there they already split out the clocks to counters to the card edge.
The clock speed of the interface is around 1MHz and the processor in the RP2040 runs at about 100MHz and both cores are used here to handle the interface. So any interface at about 1MHz is in reach with a 100MHz clock for your processor. Ish. I’ve also done this with the casio FX702P bus and the casio FX502P interface protocol, so other things are in reach. As the interface gets faster you will need a faster processor clock, and with these figures you need about a 100 to 1 ratio for it to work and be easy-ish to implement.