The ZX Spectrum ULA: How to design a microcomputer

December 29, 2010

I’ve been following Chris Smith’s zxdesign.info web site for a number of years. His redesign of a ZX Spectrum ULA using only logic IC’s was an awesome achievement.

In addition he’s wrote a wonderful account “The ZX Spectrum ULA: How to design a microcomputer” on the forerunner of programmable logic – the Uncommitted Logic Array (ULA). I was lucky enough to get his book as an early Christmas present and I found it a great read.

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Maker Faire @ Newcastle 2010

March 19, 2010

We had a great time at this years Maker Faire in Newcastle over the weekend of 13th and 14th March 2010.

My kids, who are almost teenagers, were dragging their heels as we left our parked car, totally sure they weren’t going to have a good time as we walked towards the Centre of Life.

Walking up the foot bridge to mezzanine level of the maker faire, you could hear the crackling of the musical tesla coil, then as you reached the mezzanine level you were hit by a wall of sound from the various gadgets and things beeping and booping, the musically exhibits being played and of course the Tesla coil. Their faces slowly changed as they realised there was fun stuff here and after a couple of nervous minutes getting their bearings off they went and for the rest of the day it was like trying to herd cats. 😀

I don’t think I saw a single kid, young or old who wasn’t enjoying themselves.

I was finally able to meet up, put a face to a name, with Baggers, Coley, TonyF and Leon from the Parallax and Xmos forums. Leon was being provocative in wearing his Xmos t-shirt whilst on the Parallax Propeller stand with Baggers and Coley. Coley got his own back by having on display a Xmos XC-1 board with a “powered by propeller” label stuck over the Xmos chip. Good nature ribbing 🙂

I had a great chat with John Honniball about his UK101’s he was displaying (I wish I had one for my collection of retro computers 😉 ) and his Arduino music synthesiser.

We met up with Jim and Kat from Sonodrome who were showing off their PSOC (pocket oscillator) and Tubby amps. On Sunday Jim help Sid build his own PSOC. He took it to school for a show and tell and his teacher and class loved it. His teacher was especially impressed that Haydn had soldered it all himself (with a little help).

Abs, not to be left out, spent the afternoon building a mignonette handheld LED game at the Maker table with a little help from me.

Leon has posted some pictures from the faire:

http://www.leonheller.com/Maker%20Faire%202010/

http://www.leonheller.com/MakerFaire%202010%20(2)/

Jim and Kat from sonodrome have also posted some pictures:

http://www.flickr.com/photos/sonodrome/sets/72157623644925608/

and Jonathan Street has a nice write up here:

http://jonathanstreet.com/blog/newcastle-maker-faire-2010


X-DTV – Preliminary schematic and PCB v0.42

January 7, 2010

X-DTV is a project I’ve been working on with Yvo of xcores.org. The idea is to make a XS1-L1 64 based retro-minimalist homebrew game console similar in concept to the Uzebox and Zuzebox.

Like the X-One before it, X-DTV will use Yvo’s VDP video engine but instead of driving a VGA output it will drive a NTSC TV output. We hope to get PAL TV as well but the 35.46895MHz oscillators have proven difficult to get a hold off (If anyone know where we can get them off the shelve without a large MOQ then drop me a comment).

The X-DTV’s specification is:

  • XS1-L1 64 internally clocked to 400MHz with 64K RAM.
  • 5-bit R-2R Video DAC for driving NTSC
  • 2x NES or SNES D-PAD connectors
  • SD Card interface
  • Stereo PWM audio
  • XTAG-2 Interface
  • 2x 5-way XLINK for expansion

The latest (not quite complete) PCB is below:

A PDF of the schematic is here.


Zuzebox – at last the PCB is started

November 15, 2009

I finally found some time to start the PCB for Zuzebox (a Uzebox compatible retro-minimalist homebrew game console). I’m hoping to squeeze it all into a 100mm x 100mm board so I can use Seeedstudio’s Fusion / Propaganda PCB service. The picture below only shows about half the components laid out, so I think the final PCB is going to be busy.

Zuzebox - starting PCB layout


Manic Miner on X-One Console

November 3, 2009

As promised in my post of 15th October, here’s some screen shots of Manic Miner on my Xmos XC-2 based X-One console. So far I’ve only coded level 1 and I need to add code for the SNES controllers and game play and off course the rest of the 20 levels to finish it off.

Manic Miner Lvl 1

The graphics were hand coded by extracting the pixel data and colour attributes for the first level from a Manic Miner ZX spectrum binary. A very mandraulic process involving switching between two editors and a couple of editor macros but it got the job done. I used Andrew Broads and Icemans (Chris Wild) excellent web sites for the screen layout information. The video engine is Yvo’s VDP for the XC-2 which provides up to 2 backgrounds and up to 32 sprites (8×8, 16×16, 32×32, 64×64 etc)

Manic Miner on X-One
Watch this space more to come.


Another Anniversay for me – Uzebox

October 27, 2009

Yet another anniversary.

Its a year to the day I first join the Uzebox forums. Check out the cool retro-minimalist homebrew game console at http://belogic.com/uzebox/

I was hoping to have Zuzebox, my Uzebox compatible console, prototype finished before this day but like many things time has not been my friend. But I am still working on it and I ‘ve decided to use standard modules for the USB interface as well as the Ethernet interface.


Tandy CoCo on a FPGA

April 7, 2009

While browsing other peoples blogs I found Joel Ewy’s cool blog on reimaging a Tandy / Radio Shack Color Computer 3 onto a single chip / FPGA.