A500 Mini Keyboardification Chapter two, part 2 – Progress

This one’s a good ‘un

Progress to date has been surprisingly quick – most of the ‘easy’ stuff is now done and I’ve added some extra functionality. Most of the research is now done – have spent waaaaay too long googling connectors, Pogo pins and component types / dimensions.

First print of the keyboard PCB and CAD fitout – pretty close

My workflow generally is to eyeball, sketch, measure, adjust….Then when it’s close enough, i’ll print on paper, adjust in CAD, print again then………3D print

a 3D printed space sample

I’m quite chuffed – the first 3D print seems to fit reasonably well! – there’s some adjustments needed, mainly the top of the keycaps are a little too wide, but overall for a first run, not bad.

The PCB outline

To work out a PCB outline, I’ve scanned the A500 Mini on a flatbed scanner and trace around the important parts, measuring many with calipers

the Keycap CAD
Another view – the big circles are the curves / slight indents in the top of the kecays
The CAD compared to a scan of the actual A500 Mini

Before I 3D printed the sample, I put the A500Mini on a flatbed scanner to match up the holes – as you can see, it’s pretty darn close! – you’re seeing a canvas underneath the actual CAD model of the keycaps in Fusion. The Enter key is black as i’d discovered a slight profile error, so spent half hour correcting a 0.2mm height error 😛

But, wait, there’s TWO

During the design phase, there’s a process of discovery. My main discovery for the A500Mini keyboard was that….I’d possibly need TWO PCB’s!!

If you look above at the underside of the keyboard you’ll see that there’s no space on the top for electronic components! The PCB needs to mount entirely flush to the case of the Mini. This means I’d need a PCB assembly service that can handle double sided boards (a possibility) – And to also consider a two PCB solution. There’s cost and ease of install considerations for both ways.

The A500Mini has a number of test points on the back, I think using Pogo Pins I can maybe make a clip-on PCB that can securely tap off the USB test points, meaning, a solderless install! – hence the upper white PCB that sits in place of the A500 PCB above

And, now I believe I’m going to go with a THREE PCB solution…….because…

the one with the holes in sits above the stock PCB

That’s a scale floppy disc! with a Micro SD card in
quick render of the floppy slot in the case

I saw a few posts on facebook linking to a guy that’s made a ‘fake’ floppy insert for the A500Mini – https://www.printables.com/model/170947-amiga-500-mini-a500-mini-mini-floppy-disk?fbclid=IwAR3if5FRp3opclhKoTyrkUe63XQtRW-mckg2ymWSKKi1cZvSk1KuRRkzmR4

I figured I’d go one better and make a REAL fake floppy disc. and, the best thing, after several solid days of research and CAD testing, I believe it can work 🙂 – it’ll only need two small cuts inside the A500 case and be totally stock outside. there’s a little more tweaking needed for the floppy disc design to make the MicroSD slot more elegant . I’ve ordered a whole bunch of parts to physically trial this and see if it’s viable.

So, Summary. Still a long way to go, the Keyboard itself is the priority here, the ‘floppy disc’ is just a whimsy on my part for the time being, its development is secondary and may not even make it to a real release if it’s not robust enough.

Keycap CAD – Cosmetics finished, Just needs the ‘switch’ solution figured out

Main PCB – Outline finished, needs routing, quick job to finish

Secondary PCB – Outline finished, needs routing and Pogo Pin solution testing

Tertiary PCB for the floppy disc connector – Concept – parts ordered

Fourth + Fifth PCB’s – the floppy disc itself – parts ordered.

Firmware – Standard keyboard layout is done! – Just needs tweaking and testing on a real A500 Mini

Author: Bleugh

Early Fourties, Wife, two kids in primary school. Both of us work full time...5 years now we’ve been Back in Blighty after a decade away...It's a new country for everyone! Still finding time to tinker!

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