ZX81+35 Clone

[dasteph]

Certainly looks the part, quite an amazing home for the Clone.

[Moggy]

I had the ZX80 replica case on Shapeways printed a few months back, which now houses my ZX80Core:





I used the case rivets from SMR to complete the case, and drew some stickers up to approximate the original labelling.

The case finish is a little rough but I'm guessing an acetone bath might help there. I'm happy enough the way it is though.

If anyone needs the sticker file, let me know and I'll host it somewhere.

B

That,Brendan, is a thing of rare beauty.

[Paul]

Yes, please host the stickers!

[balford]

No problem gents, here they are http://www.bennyalford.com/zx80labels.zip

B

[mahjongg]

Okay, I looked, and estimate that placing an extra resistor near the reset logic won`t be a problem, so I added R54, and moved J7 to a more logical place in the schematic, and did a bit of cleanup, so here it is, the (hopefully final) schematic of the ZX81+35 revision 2.2.

ZX81+35 REV 2.2-1.png

(671.19 KiB) Downloaded 294 times

Obviously, if someone sees a bug, please mention it here, I'm very thankful for any bug-fixes.

By the way, my joystick port logic has been tested (on a Spectrum) and works when using the right FETs, I thrust they will work on this ZX81 clone too, but at the moment I'm more occupied to get the basic ZX81 logic to work well, so I will probably leave it off initially, as well as the "GPIO/LCD/sound" logic.

I have now started on the layout of this version, it will be hard to make room for four new SOT23-5 IC's.

[mahjongg]

Did some placement strategy on the Altium 3-D mockup I made. I hope I can place and route the four extra SOT23-5 devices, when I manage that, the board will look like this when it is finished:

ZX81+35 revision 2.2 preview.png

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[Paul]

Did you consider using a Plcc Z80? That might free up some space.

[RetroTechie]

Micro-USB for power: has pro's and cons, but certainly not a bad choice.

Any chance of including that joystick connector on the board itself?

GPIO connector is a nice touch. Wouldn't be bad to have some more pins on that connector though. ZX81 people are rather 'hacking-minded' people, you know. So they'll find uses for whatever I/O pins you stick on there.

[PokeMon]

Mahjongg,
you have to be rich to use Altium Designer.

[mahjongg]

Did you consider using a Plcc Z80? That might free up some space.

Yes, I did, but after finding out that Farnell only sells the Z80 in DIP, I decided to go with DIP, its more authentic, and probably better available and cheaper. Cost and long term availability drove many of the (component) choices. For me it's possible to order all parts from one source (farnell), but I looked at connectors and such that will still be available in say ten years time.

I think that in this design I will manage to fit everything onto a 10 x 10 cm dual sided board, size and dual sidedness was also cost and availability driven, many ultra cheap Chinese PCB manufacturers offer better prices for boards-to 10 x 10cm.
I order my boards at eurocircuits, for a good quality board, very important for prototypes, and 10 x 10 cm is still affordable, but for ultra cheap PCB's its better to order them in china.