C64 Mini Keyboard – More!

img_3245-1C64 MINI KEYBOARD SCHEMATIC 1Small updates –

Slowly but surely –

Did some research on diode packages today and came across the wikipedia page!


Why? – SMT soldering can be slightly tricky for some, most people soldering however are happy with Through hole components

After doing quite a bit more research, it seems that you can use pretty much any diode for anti-ghosting on keyboards – Schottkey, Germanium, even standard signal diodes.

However, to fit in the space on the keyboard of the mini needed a particular sized package! I found one that’s cheap and readily available 🙂

The SMT packages I’m using are SOD-123 

I’ve now added an additional footprint to the PCB – a DO-34 (AKA a lot of other names also :-)_ https://www.nexperia.com/packages/SOD68.html

This means now you can chose which Diode type to use – SMT or Through hole! – took hours to re-design the matrix circuit and line things up nicely on the PCB…after seeing the results, i’d be sorely tempted to also do an SMT switch outline also, BUT, the two suppliers i’ve tried to buy from, I still haven’t received anything several months later, may save that for a REV3 when the stock of REV2’s run out


So, here’s the new PCB – not much different looking – except the extra gold holes above and below each diode (or, to the side on the F-Keys)


and, a few minor other differences…that are better shown in the below photo, a PCB on top of a printout of the Rev2 PCB


Points to note – all the keys are in exactly the same position – you can just about see the printed circles in the smaller through holes…

The mounting post holes are smaller (3mm) now so they sit on top of the standoffs in the case. The’re also shifted ever so slightly – just over 1mm….

Still to do a final ‘print on card’ and line up, But, i’m now much happier!

Also, the other difference – in the 3D render – Two rows of holes at the bottom ‘in’ the space bar area – This allows two different widths of Arduino pro-micro to be used, as it seems there isn’t really a standard…


I was contemplating adding a USB hub chip – but that gets things too complicated for logistics and component ordering, instead , i’ll be installing a USB hub module – final details TBC, but i’ll be able to keep the joystick port free! – this mod will be ‘invisible’

it WILL require a little bit of very easy soldering to become ‘invisible’ but i’ll keep that to the bare minimum, i’m aiming for just the 4 USB wires……

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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