PET/CBM-II keyboard interface?

From: Anders Carlsson (
Date: 2007-09-25 09:05:41

Hi, list.

The past weekend I went and picked up a new batch of PET/CBM items, mostly 
random bits of which some I'm keeping. Earlier this year I got a whole 
cardboard box full of loose motherboards, and grabbed a few keyboards to go 
with them. My idea was, and still is to build some video adapter and power 
supply to make keyboardless PETs out of them.

Among the items I picked up this time were two loose 3000/4000/8000 series 
power supplies, a dead CBM 710 and a PET-VRF - a video interface that 
outputs composite video or RF signal. Unfortunately it doesn't work very 
well. On 40 column PETs, I get an almost readable picture that scrolls in 
every direction. On 80 column PETs, I mostly get a bit of pixel junk, still 
under constant scroll. The video interface was once built in Sweden 1979, so 
it should be compatible with my PAL TV's and monitors.

My batch of motherboards includes three 3032 motherboards, one 4000 series, 
two 8000 series and four 710 motherboards. Through a lot of temporary 
connections, I have verified all to boot and I have reason to believe they 
all work. My batch of keyboards however is limited to two 3000/4000 
keyboards (one partly faulty), two 8000 keyboards and one 700 keyboard.

Certainly I will be able to replace the dead motherboard in the CBM 710 for 
a working one and get a complete unit with both monitor and keyboard. But 
assuming that I can build some video adapter - perhaps Nicolas Welte's one 
or one of the older ones like Nick Hampshire's or the UK PET Users Group - I 
would like to come across some ideas how to use a micro controller to create 
a keyboard interface/adapter.

I haven't researched the topic too well, and my electronics skills are quite 
limited, but I understand it is not completely unheard of. There exists some 
projects to connect an AT or PS/2 keyboard to a C64 (or vice versa), and I 
saw something about a C128 keyboard too. I understand that I have to deal 
with three different types of PET keyboards, but currently I have access to 
all three for testing.

Does anyone have any pointers or ideas where to start? I'm fairly good at 
understand most kinds of programming, so if most of the work is about 
programming a micro controller with a matrix and decode characters, perhaps 
I can learn it.

In the mean time, if anyone has experience with the mentioned video 
interfaces, I'm all ears. Will every PET (model) have its own frequencies, 
so I'm forced to use an advanced multisync monitor needless of which 
interface I use? Nick Hamshire's design mentions that one could alter the 
value of a resistor to improve the sync rate. Perhaps the two older designs 
will only work on 40 column PETs anyway.

Best regards

Anders Carlsson 

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