C=key adapter 3.0a quick look

About a year ago, I had a go at rigging an Arduino to work as a PS/2 adapter. That adapter is working, but the software needed patching. I got it into semi-decent state but it still leaves a lot to be desired. (Shift+cursor keys etc work a bit randomly.)

In the meantime, I also ordered this ready-made solution from Retro Innovations, the C=key 3.0A.

Apart from modest soldering skill you will need some sense in building electronics, as the (not included) instructions need some deciphering. But if you follow them step-to-step precisely it should come out good. I guess you can also order them soldered. I perhaps wanted to avoid having the PS/2 connector positioned, but as it turns out it was a better idea to use that part anyway.

The board has provisions for both female & male 20-pin connector. I could have avoided soldering the other part in, had I given it a bit more thought.

Because there was a capacitor in the way, I could not fit the board directly on the C64. So I went for a long-ish drive cable. I once found a bunch of these from a flea market.

Bonus points for including proper holes in the board for easy attachment in your own projects. I'm not yet sure where I'll use this.

The adapter worked at the first attempt. My impressions were that this is much smoother and bug-free than that DIY board.

But it turns out this C=key adapter is not without problems either.

Although the key mapping felt great at first, I soon found the cursor keys did not work. Then I learned I need to change the keymapping style. I can enter the "menu" by pressing CTRL+ALT+BACKSPACE.

There,

1. C64 Symbolic
2. C64 Positional
3. C128 Symbolic
4. C128 Positional

(CTRL+ALT+BACKSPACE exits the menu.)

Using selection 1. (C64 Positional) the cursor keys started working and all keys are mapped according to the PC keyboard. ...according to an US keyboard, that is. Sigh! So the keys work but everything is in an alien place.

While testing the keyboard I sometimes came up with gibberish. I also managed to get the adapter locked quite easily, which often followed from pressing Return, but other keys too. Using the CTRL+ALT+BACKSPACE combo a few times the adapter recovered.

The site does say "This is still considered a project, not a complete product. I’ll try to help with issues, but it’s still a work in progress."

I did clean the adapter up and wiggled the cables a bit and got a better response out of it. Who knows, it might be my soldering and construction was a bit botched. I'll have to make sure the board and the cable do not move when pressing the keys.

These were of course the very initial responses to this adapter, and further examination should reveal how well it works in the long run. Possibly, a PS/2 to C64 keyboard adapter is a device that simply cannot be made to work 100% reliably and in a satisfying way, but this is already quite good.

PS/2 keyboard on the C64

(Or, the Pizza Box C64 part III)

After building a desktop case for the C64, I wanted an external keyboard.

Browsing the web I get the impression that people want to convert their existing C64 keyboard to work on a PC rather than the other way round, but still I was sure I had seen a PS/2 adapter for C64. And yes, there is the C=key Keyboard Interface, but it's quite expensive and not always available.

Then I came across Robert VanHazinga's solution at GitHub, which uses Arduino Uno/Due, MT8816 chip and a minimal amount of parts. Although it seemed confusing at first, after getting to know the chip a bit it is really quite clearly documented and can be compiled easily.


MT8816

As far as I understand it's not really possible or healthy to connect an Arduino directly to the keyboard header pins (the CIA chip in fact). An intermediary chip is recommended.

The MT8816 switch array chip comes in handy, as it can specifically produce a connection matrix (X0-15) out of X-Y coordinates (AX0-AX3 and AY0-AY2). The output is built through setting connections between the "coordinates" and setting the matrix using a combination of DATA and SWITCH. RESET clears the whole array.


Breadboarding

First I built everything on a breadboard at one go but it failed to produce other than random characters on screen and no visible reaction from the keyboard. This was still somewhat encouraging.

I slept over it, had a deep breath and put the C64 aside. I connected the PS/2 keyboard alone to the Arduino and powered it from the PC USB. I saw that on power-up the keyboard actually flashed its LEDs, something that had not happened before. So perhaps the problem had been some kind of oversight with the cables I guess.

I added a routine for blinking the internal LED to see if it receives the PS/2 keys, and sure it did. Sadly I had to remove this internal blinker as it shares the PIN13 which is needed by the software.

Then I rebuilt the setup on that and it worked!

It became quickly apparent not everything was perfect. Testing the keys, I saw that the 1st keypress after any reset always somehow fails. Left and up cursor are simulated and don't work that well with key repeat. Some keys such as pause/brk and prtscr/sysrq messed things up, and also result in a freeze.

Generally,  fast typing with shift, such as typing the " can result in a keyboard freeze. Actually, if I press shift, press the key to get the ", and if the shift is released before the other key, it freezes.

In this implementation F12/reset clears the freeze, which is a relief.

I also noted that with Final Cartridge III, the bypassing of the GUI by pressing run/stop while booting won't work - I suppose the Arduino software and/or the keyboard can't be yet online at that point.

On the positive side, typing with normal keys works and there were no random hiccups or system crashes. I started to warm to the idea that this could work well enough and most of the problems might be software-based.


Building the board

Satisfied at this, for the next stage I soldered the connections on a prototyping board, with a kind of Arduino "shield". The main connection between the C64 motherboard is with a hard drive ribbon cable, which has 20 pins wide connectors. With some more thought, the board could have been planted on top of the keyboard header but I felt more comfortable with the ribbon.

I thought about having the Arduino USB connector accessible from outside, but after aligning the chip, keyboard header and the Arduino on the board, I couldn't get it to where I wanted it so I gave up the idea for now.

Some day I will have some of that glow visible outside.

Soldering the headers and sockets was easy, but making about 50 connections with wire was boring. The composition was a bit too tight after all, which made the work more stressful. The learning from here was that when making a board by hand, I should make generous space for easier soldering rather than try to optimize prematurely.

Even then the board was not compact enough to fit inside the corner compartment of my case, but the middle suits just as well.

The first boot with the soldered board was a disappointment, but after carefully cleaning the spaces between connections and checking the cables I started to get characters out again.


Case fitting and cleaning up

There still remained the task of attaching the PS/2 connector to the case. This was done with a round screw-in PS/2 connector shown below.

I attached it to the right side, near the joystick ports. Behind the computer would have been perhaps more appropriate, but there's very little space there and I didn't want to pull any more cables across the motherboard.

Just about ok for the 3mm thickness

Inside the box, I also needed to cut the center wall a bit to make a passage for the ribbon cable.

For now I did not attach the keyboard adapter board, as I may still need to change it a bit.

For once, a part that behaved nicely.

More to do:

-Check if the software could be improved a bit and fix the keymap to suit my needs
-Paint the case, put a logo on it or something