Replacement Keyboard Project Update

[GregZone]

I've been doing some more research, and I was now thinking along the lines of perhaps instead using a MT8816 (i.e. instead of 2x MT8808's), and also perhaps going for the RaspberryPi Pico MCU board, as it is cheap and provides up to 26 GPIO pins.
The MT8816 is available either in DIP40 or PLCC44 package, which would also provide some PCB space saving (over 2x DIP28 MT8808 packages).

If I calculated correctly, we'd need 24 GPIO to support an MT8816 + PS/2 Keyboard + 2x DB9 Game Ports, so by moving to a Pico we would presumably enable enough pins to support both left & right joysticks.

Also, for my needs, I want to interface directly to a PIA (so, just 12 port pins - PB0 - Pb7 and PA0 - PA3), therefore I'd want to include diodes and pull-ups on-board.
But, to make an interface board that would still be usable as an actual Creativision PS/2 Keyboard & 2x Joystick solution, but also usable for interfacing directly to a PIA (on a CreatiVision re-creation), then perhaps the PCB is designed to have both direct 10-pin connectors (for connecting to the CreatiVision ports), as well as a diode and pull-up fed connector for allowing a direct raw PIA port connection?
This would make for a dual purpose solution.

Tom, do you see any problems with the direction I'm dreaming up?

[Scouter3d]

Hi GregZone,

please feel free to build on our work, i am sure, we are honoured :0)

As i guess @username@ is also ok, with you browsing thru his code, you find the kicad files and arduino code in the attached .zip...

As for the Raspberry Pico, i guess you will need Levelshifters, as it has only 3.3V I/O Pins ...

It has really been a while since i worked on the keyboardinterface, and i have to look into the MT8816, as i do not know it...
I used 2x 8808 because using only one did not work and i fried 2 PIAs working this out ;0)

But with a Pico i guess it would be possible to completly simulate the PIA? (At least for your internal solution?)
But then i guess you will still like to keep the original controllers as a possibility, so you need the PIA

Cheers, TOM:0)

[GregZone]

please feel free to build on our work, i am sure, we are honoured :0)

Thanks Tom!

As for the Raspberry Pico, i guess you will need Levelshifters, as it has only 3.3V I/O Pins ...

Indeed! On further look, I'm thinking we mightn't need as many GPIO pins, as I first thought.

The AY2 input on the MT8808/MT8816 could just be tied low (as we're only using the Y0 - Y3 outputs).
Also, the Master Reset input could instead use a power-on reset circuit, saving another GPIO and also ensuring all switches are always off on power-up.

So perhaps 7x GPIO for the MT8808's (or 8 for a single MT8816), 2x GPIO for PS/2, and 12x GPIO for 2x DB9 Joysticks (or 10x GPIO if only supporting 1 button each).
So, that would make a max of 22x GPIO used, or a minimum of only 19 GPIO (for 2x MT8808, PS/2, and 2x Joysticks with only one button).

Since the 5V 28-pin 8-bit AVR MCU family have 22/23 GPIO, then perhaps I'll take a look at a possible AVR based solution?

Lots of projects on the go, but with the work you've already done, this looks like one I'll definately add to my to-do list!

[GregZone]

Well, it took me a couple of months and I went through 3 PCB revisions, but I'm finally happy with the end result.

For anyone interested, my own CreatiVision Controller journey is documented here: Minimalist Europe Card Bus (MECB) – 6502 CreatiVision re-Creation (Part 2)