{"id":22470,"date":"2025-02-22T11:49:13","date_gmt":"2025-02-22T10:49:13","guid":{"rendered":"https:\/\/www.recantha.co.uk\/blog\/?page_id=22470"},"modified":"2026-01-23T17:42:59","modified_gmt":"2026-01-23T16:42:59","slug":"the-psion-5-raspberry-pi-conversion-project","status":"publish","type":"page","link":"https:\/\/www.recantha.co.uk\/blog\/?page_id=22470","title":{"rendered":"PsionPi Cyberdeck – a Psion 5 \/ Raspberry Pi project"},"content":{"rendered":"

The project: a compact cyberdeck with a built-in keyboard<\/h2>\n

I was recently selling some HP Jornada PDAs on eBay, having spectactularly failed to get them online via a wifi PCMCIA card. What I really wanted, I decided, was a Raspberry Pi in a compact “Cyberdeck style” unit.<\/p>\n

The failed project: HP Jornada conversion<\/h2>\n

I did look at converting one of the Jornada 680s<\/a> that I had as the keyboard was, if a bit small, adequate for my needs. I looked for a converter of some kind to take the ribbon cable used by the Jornada’s keyboard to a USB output, but I looked in vain, hence the decision to subsequently send them to eBay.<\/p>\n

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However, I did come across this Psion 5 keyboard adapter<\/a> by Rasmus Backman<\/a> on Tindie and thought: “Yes, that’s what I want, but for the Jornada.” I found this project<\/a> which had remixed the Psion 5 adapter for the Jornada. However, it wasn’t as simple as buying from Tindie – I would need to get the boards manufactured. Although the KiCad files were there, I just didn’t have it in me to get a surface-mount board manufactured as a PCBA – it would’ve been expensive, plus I had no idea what to do if the components weren’t available. Would I have to hand-solder the surface-mount components? Probably, and that didn’t sound like much fun.<\/p>\n

Moving on! The Psion 5<\/h2>\n

With Rasmus’ adapter available for a decent cost, I decided to go for a Psion 5. I looked on eBay and found a few lots for old Psion 5s that could be used as the donor unit for the project. Mostly, these were out of my price range but, thanks to selling the Jornadas, I could afford around \u00a350 for the unit. I didn’t need a 5mx (the better, more expensive version), just a 5 (which had lower memory and was considered inferior, although it seemed identical, design-wise). The keyboard was all that mattered. If it was only “for spares”, even better, but all I could find was a lot that included a lot of spare parts for a lot more money, so a working model was where I went. In the end, it cost \u00a345, a good investment. It was slightly faulty (see the picture below with the bad pixels in the middle) so I wouldn’t feel bad about taking it apart and disposing of most of it!<\/p>\n

\"Image

The actual unit I purchased<\/p><\/div>\n

Was conversion of a Psion the only option?<\/h2>\n

Retro tech is to be valued, and even a slightly faulty unit is still usable. Could I use the Psion 5 as it was? I looked at a few options.<\/p>\n

    \n
  1. Digital assistant via serial. I came across this MagPi article<\/a> which described a project to use the Psion as a serial terminal for a Pi via a cable (and lots of adapters and gender-switchers!)<\/li>\n
  2. Kian Ryan’s sidecar. This was my next find – a 3D-printed module to allow the Psion to be a serial terminal over wifi<\/a>. This was fairly neat and allowed wireless connections.<\/li>\n<\/ol>\n

    Neither option was quite what I wanted – I really wanted a) a colour screen and b) a proper desktop environment.<\/p>\n

    What’s the plan, then?<\/h2>\n

    I started to assemble parts for the device. I knew that I would eventually have to 3D print something<\/em> for it. This was likely to be a new “back” to the unit to house the screen and the Pi, but I thought I would likely to have to print a new “bottom” to the whole thing to squeeze a decent battery in. It all depended on taking the donor Psion 5 apart and seeing how much room there was left once I removed the main circult board. Most importantly, I really wanted to keep the hinge mechanism which I have always thought rather cool (I know, what a geek!)<\/p>\n

    Here’s the hinge mechanism sort-of in operation from the patent application – the unit is a clamshell and the screen lifts up and pushes the keyboard forward.<\/p>\n

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    Which Raspberry Pi?<\/h2>\n

    Initially, I had the thought of using a Raspberry Pi Zero 2W, I needed it as small as possible, but I also needed wireless comms. However, I also realised that I’d need the DSI connector of a full-sized Pi. That’s the “DISPLAY” connector on the left-hand side. This takes a ribbon cable, keeping things neat and doesn’t have the problem of needing a big connector sticking out of the HDMI slot. I decided that a Raspberry Pi 3A+ would be ideal – it’s fairly powerful, although the lack of memory on it does cause me a few problems. I could<\/strong>, if I have enough room, go for a Raspberry Pi 4B, which would be more powerful and keep within what I think I’ll be able to deliver power-wise. However, I would need to detach things like the Ethernet connector and all the USBs in order to keep it to size. I’d also need a USB interface (for the Psion keyboard) and the idea of having to desolder the double-height ones and\u00a0then<\/em> solder on a single USB filled me with dread!<\/p>\n

    Therefore, a 3A+ would have to do:<\/p>\n

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    \nWhich display?<\/h2>\n

    As I’ve said, I wanted\/needed to use a DSI display. In previous years, all that was available was the 7″ Official Display. I’ve actually got one of these, so did consider it. Here’s a picture of the back:<\/p>\n

    \"\"<\/p>\n

    As you can see, there’s a driver board on the back. From my own experience, I know this takes up a lot of space in terms of depth, so I looked at the version 2 display as well<\/a>. This would have been ideal (it’s not as deep), but it’s the wrong shape and size. It’s just too big<\/a>. Fortunately, things have progressed since 2014 when the Official Display was launched, and there are now a plethora of DSI displays out there.<\/p>\n

    The donor Psion hadn’t arrived and I wanted to get ahead of the game, so I reached out on Mastodon<\/a> to ask the community if anyone would mind measuring the screen and surround of a Psion 5. Fortunately, maker Alfred Chow<\/a> came to my rescue and did the necessary measuring. Here they are for reference:<\/p>\n

      \n
    • The visible screen is 137mm x 54mm<\/li>\n
    • The actual screen area is 145mm x 60mm.<\/li>\n
    • The rest of the case surrounding the screen is 172mm x 75mm<\/li>\n<\/ul>\n

      This was just done using a tape measure, not calipers, so this is to the nearest millimetre, which is ideal as I wasn’t going to 3D print anything\u00a0yet<\/strong>.<\/p>\n

      I went shopping and found that the supplier with the most choice was Waveshare, who are overseas. However, venerable online shop The Pi Hut has a massive amount of their range<\/a>. I went through the options and found the one that was closest in size to the original Psion 5 screen. This was a Waveshare 6.25″ DSI capacitive touch screen<\/a>.<\/p>\n

      \"\"<\/p>\n

      Now, this wasn’t a\u00a0perfect<\/em> match (hence me probably needing to 3D print a new back of the case, and it’s probably a bit too thick, but it’s worth a try. If I don’t use it for this project, it’ll make a very nice little status monitor for some other things.<\/p>\n

      Dismantling the Psion 5<\/h2>\n

      First thing’s first. I would need to dismantle the Psion 5 to get at the keyboard and its ribbon cable, which I would then plug in to the Psion 5 keyboard to USB adapter PCB from Rasmus Backman<\/a>.<\/p>\n

      Fortunately, someone has documented the procedure to disassemble the Psion – take a look at this page<\/a>. Here is a more extensive guide<\/a> and again in PDF form<\/a>.<\/p>\n

      I also found this file – the Psion 5 Service Manual (from November 1997!)<\/a> which could have come in useful.<\/p>\n

      There are various “teardown” videos on YouTube. For instance:<\/p>\n