Electronics > Projects, Designs, and Technical Stuff
Cloning a Commodore PET-2001
GK:
Well the computer is now finished electrically. Now I just have to mark out and drill and tap the mounting holes for the lid and fashion the last length of 10mm square rod which screws to the inside top of the front panel, but that is enough for this evening.
I'm largely done with the PDF documentation - just need photos of the completed unit to finish it off. Once I'm done with the documentation I intend to publish the whole thing (Gerber files, ROM images, BOM, etc) on a single dedicated page on my website. This will probably take another couple of weeks.
jeffheath:
Nice! Love the neat wiring, and the Altair look. ;D
GK:
Thanks.
Hmm, I dunno though - I think it would need a lot more toggle switches to remind me of an Altair :)
martinjaymckee:
Just wanted to chime in on what a cool project this is. I agree with previous posters about the implementation being beautifully clean and well laid out. I certainly would love to have something like that in my workshop -- for now I'll have to stick to my Raspberry Pi to control things. I'm sure your new PET will do well!
Cheers,
Martin Jay McKee
GK:
OK, I still haven't finished the PET documentation yet. Seems I'm crap at estimating time frames for hobby projects. I've had a diversion, which I just finished loading and testing this evening.
This is the "deluxe" cassette port analogue interface which I mentioned some time earlier in the thread. Plugged into the PET's (or C64's or VIC20's, etc) cassette port, it allows almost any audio recording/playback device to be used instead of a propriety Commodore "Datasette" for program and data storage. The encoding method Commodore used is polarity sensitive, so provision is provided (for compatibility with other recorders) in both the read and write signal paths to invert the signal. A data bit is represented by a full cycle of a squarewave of a specific period immediately followed by another full cycle of a squarewave, but of of a different period. Which way around the periods are depends on weather or not a 0 or a 1 is being represented and all timings are measured from negative-going edges only.
The "read" signal is bandpass filtered, limited and then sliced by a comparator with hysteresis. This circuitry in practice does a great job of cleaning up and giving successful data transfers with rather crappy/noisy/ringing/low-level playback signals. When data is being properly received in the read signal chain the activity L.E.D. will flash as a constant rate of approx 2.8 Hz. I've been loading and saving programs from and to my crappy Digitech portable voice recorder.
Now I just have to build it into a fancy instrument enclosure.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version