Burn-Out, Revisiting The Psion WiFi Pack, and Other Miscellany

A project log for The Last Psion

Resurrecting Psion's SIBO/EPOC16 Platform For The 21st Century

Alex BrownAlex Brown 10/01/2020 at 08:221 Comment
Psion Series 3a "Dragonskin"
Psion Series 3a with custom green case. I think of it as looking like dragon skin.

Near the end of last year I hit a wall. After spending months trying to learn VHDL and feeling very much like I was failing, I decided to put my participation in the project on hold. I had burnt out and it was time to walk away, if only for a little while.

Now, almost a year on (and what an insane year it's been!), I've recently got in the mood to take another look. On a personal note, I'll be approaching it a little less frenetically — I'm working on a couple of other personal projects and want to try to share my time between them, not to mention having a day job as well. But my enthusiasm for the project is still strong and I really want to see where it goes, even if it takes me a few years to get there.

As before, my next step is to attempt to recreate Psion's ASIC4 chip in VHDL and then get it running on an FPGA. This, to me, would give the retro community something very interesting to play with. First, it would provide a never-ending non-destructive supply of ASIC4s. And second, it would make ASIC4 customisable.

Both of these points are important for the WiFi Pack, but would also be really useful for other projects. For example, having the ability to translate SIBO-SP into SPI would mean SD card access.

Early last year I bought a few breakout boards that were, in short, the right size for an ASIC4 chip. My plan was to cannibalise an SSD, remove its ASIC4, solder it to the breakout board, and then basically build a massive SSD. That way I could easily test all of ASIC4's pins and see exactly when traffic was happening. For example, precisely when are the address lines made active to write to the on-board memory?

But so far I haven't done this. I've not been confident enough with my own surface-mount soldering skills (let alone desoldering) to risk breaking an ASIC4. However, I know how much it would help.

Another thing I've done is message Zebra Technologies (the current owner of the Psion SIBO/EPOC16 IP) on Twitter to see if they can help. I'm hoping that they might have some old backups of, say, a server around 1995 that might include some documentation on ASIC4 and ASIC5. If anyone fancies giving them a nudge, feel free - I could use all the help I can get!

I'm also planning on moving the site around a little in the coming weeks. The Documentation project will be shifted to its own subdomain, and the main site will be some static pages including links to resources and (hopefully) a few useful downloads like the original SIBO C SDK and HDK. There are some concerns about copyright, but this is all pretty much abandonware so I'm hoping Zebra won't mind too much.

On the subject of documentation, I have a pile of hardware — some purchased, some kindly given to me by very generous people — that I'm slowly going through, testing and tearing down. One thing I'm interested in is the Honda RS-232 port on the 3c, 3mx and Siena. It turns out that this isn't a pure RS-232 port, and there might be some SIBO-SP pins hidden away. Using a Siena SSD drive, I need to solder together a little man-in-the-middle cable to monitor those pins to see what they do. I'll update here when I get around to putting that together.

I'm also still digging through an archive that a former Psion exec sent me early last year. There's a huge amount in it (just not much about ASIC4), which I would just publish if it weren't for the potential copyright issues; the SDK has been available on various sites for a while now, but this archive includes schematics for things like the MC range of laptops that (I think) were never released to the public. (Hey, Zebra, nudge nudge...)

One other thing I did... I bought a display cabinet for my Psion kit. Here's a photo. On the top shelf is an MC400. Those Really Useful Boxes at the bottom are project boxes, each one stuffed with pulled-apart SIBO machines. It fits in nicely in my old Victorian house.

So yeah, that's where I am so far. Not sure when I'll be updating this next, but if anything crops up I'll let you know. In the meantime, please feel free to message me with questions and missives of undying support.


Stu.axon wrote 10/11/2021 at 11:57 point

What a great project, from what I hear VHDL is notorious for being a pain, so you are in good company with that.

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