Re: C64 Tower - keyboard
========================

Subject:      Re: C64 Tower - keyboard
From:         Nicolas Welte <welte@chemie.uni-konstanz.de>
Date:         1998/03/11


Martijn van Buul wrote:
> Making a small circuitry that emulates a C64 keyboard from the scancodes
> it receives from the PC-keyboard, that'd be a far more better idea.

Yes, I agree!

> Actually, all you need is a microcontroller, reading the COLUMNS-port
> from CIA1 port A, and writing the appropriate LINES-value to port B,
> depending on the keys pressed.

But that would not be very compatible. I think there are some programs
(especially games) which use a custom keyboard code which makes some
effort to distinguish actual key presses from joystick moves. You could
also use port A as input and port B as output, which would render your
circuit inoperative.

There are much better solutions, I think they are called analog matrix
chips. They basically represent a switch matrix in a chip and are
available as 8x8 or 8x12 matrix (among others), which would fit the c64
and c128. If you combine one of these with your microcontroller, then
you have the final keyboard replacement. Of course you had to deal with
all those remapping problems, just like emulators do.

> A simple 68HC11 would do nicely. It has
> enough I/O ports, enough RAM, enough EEPROM to store the needed program
> in.... Easy!

Hmm, I couldn't do it. If it's easy for you, then please do it :-)
B
>  (the LEDS are controlled that way). However, XT-keyboards are hard to
>  obtain these days...)

Some older AT keyboards have an XT/AT switch.

Nicolas