Chroma 81 - SCART and Colour interface for the ZX81

Discussions about Sinclair ZX80 and ZX81 Hardware
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PokeMon
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by PokeMon » Wed Apr 06, 2016 1:04 am

I got a picture in the meanwhile with the ZXmore when using the ZX81 instance with disabling task switching and removing (or shortening) the 1k series resistor in the clock line to the edge connector which is used for some special reason. Without task switching it is not easily possible now to load any programs - so not a convenient way. I am thinking further if it is possible to modify the loader code and put a separate driver on a desired instance to use this feature. But this is more future stuff.

I think the main problem is the time point you use to sample the video shift register data which maybe slightly different from ZX80 and ZX81 and some clones as well. Due to very fast access times it should be possible to sample this data maybe a half clock cycle earlier as modern SRAMS have access times of 70 or 55ns and deliver the addressed pixel data much faster than a usual ZX81. Not sure if such a ctrl can be made easily but in my eyes would need much logic in a CPLD (1 or 2 macrocells only).

Having a back porch on the green channel would be nice if you ever decide to change anything on a second batch. But all up to you, just a proposal.

Fruitcake
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Fruitcake » Mon Apr 25, 2016 1:25 am

The CPLD is crammed full and it was a struggle just to get the current logic to fit. So I don't think there is scope with the current board to make further enhancements.

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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Fruitcake » Sat Jun 03, 2017 5:53 pm

A version of Mazogs is now available that directly controls the Attribute Colour Mode of the Chroma interface. It can be downloaded from here.

It builds upon the disassembly I produced of Mazogs and the subsequent flicker-free conversion I created for the ZX80 that converted the BASIC program into equivalent machine code.

The colour scheme for the conversion is based upon that used in the game Maziacs, which was Don Priestley's adaption of Mazogs for the Spectrum.

Mazogs.gif
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Mazogs Game.gif
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Last edited by Fruitcake on Thu Jun 21, 2018 1:21 am, edited 1 time in total.

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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Fruitcake » Sat Jul 29, 2017 11:40 pm

A colour version of Software Farm's classic game Rocket Man is now available for use with the Chroma interface. It uses the Attribute Colour Mode to achieve a colour resolution of 192 x 32. The conversion also includes fixes for several of the bugs present in the original game (a full list the bugs can be found in the Rocket Man commented disassembly).

Colour Rocket Man can be downloaded from here.

A video of the game in action can be view on YouTube.

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Last edited by Fruitcake on Thu Jun 21, 2018 1:19 am, edited 1 time in total.

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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Fruitcake » Thu Sep 14, 2017 2:24 am

I've just released the Chroma Program Enhancement Creator utility which runs on a Windows PC and provides a graphical interface for defining replacement character sets and colour schemes to improve the appearance of existing ZX81 games. Once the user definable graphics (UDGs) and / or colours have been defined, the utility can automatically generate ZX81 loader programs that configure the desired mode(s) of the Chroma interface.

The utility supports the generation of the loader programs for three populate UDG schemes, allowing the same character definitions to be used with other hardware as well as the Chroma interface, e.g. original Quicksilva Character Board, dk'tronics or Kayde Graphics ROM board when fitted with the optional RAM, and modern UDG interfaces that support the CHR$16/CHR$128 mechanism (a mode which Chroma currently doesn't support). This allows a replacement character set to be defined once and then shared across multiple UDG hardware interfaces. As a result other UDG interfaces can benefit from the character definitions already created for use with the Chroma interface, and when character sets are created targeting those other interfaces they could also be used with Chroma. Hence everyone can share a similar enhanced gaming experience no matter what physical UDG hardware they have.

Generated programs can be saved in a variety of formats allowing them to be easily used with Chroma, ZXC ROM cartridges, the ZXpand interface, and as cassette files for use with emulators or for loading into a real ZX81.

Character and colour definitions can be saved as XML files, allowing them to be reloaded at a later date. Since the files are in a human-readable and fully documented format, the files can easily be supported / generated by other utilities, e.g. equivalent Creator utilities written for Apple and Linux PCs.

A selection of existing character definition files for a variety of games, including a selection of fonts that can be used as the basis for creating future game character sets, can be found here. And a selection of colour definition files for a range of games can be found here.

sirmorris
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by sirmorris » Thu Sep 14, 2017 10:39 am

Image Top work Paul! I love the loader export feature. You can't beat a good end-to-end solution. :ugeek:

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Andy Rea
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Andy Rea » Thu Sep 14, 2017 10:58 am

Looks absolutely fabulous... gonna have to give it a whirl sometime. Thanks for sharing

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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mrtinb
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by mrtinb » Thu Sep 14, 2017 11:57 am

I found that difference with UDG64 and UDG128 are that UDG128 have I-register + 1. But how is QS different?
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

olofsen
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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by olofsen » Thu Sep 14, 2017 7:45 pm

It seems that with QS, I remains at $1E, but the pixel data come from $8400; from http://problemkaputt.de/zxdocs.htm

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Re: Chroma 81 - SCART and Colour interface for the ZX81

Post by Fruitcake » Thu Sep 14, 2017 11:45 pm

[/quote]
Andy Rea wrote:
Thu Sep 14, 2017 10:58 am
Looks absolutely fabulous...
:D

sirmorris wrote:
Thu Sep 14, 2017 10:39 am
I love the loader export feature.
The game enhancements by Villordsuch to Invasion Force (Artic Computing), Meteor Storm (dk'tronics), Galaxy Jailbreak (Romik Software) and Jetpac 81 (J. R. Todd) have all been create using forerunners of the utility to generate the loader programs. The most recent addition of Krazy Kong (PSS) was the first to be produced by using an earlier version of designer.

One thing I forgot to mention in my earlier post is that the utility produces separate loaders for applying colour and UDGs. If both options were selected and the chosen output format was as a single tzx file then when the colour loader is loaded it checks whether Chroma is present and if not then continues to load the game file. The upshot being that the same tzx file can be used with different hardware irrespective of whether Chroma colour is present or not.

olofsen wrote:
Thu Sep 14, 2017 7:45 pm
It seems that with QS, I remains at $1E
QS mode doesn't use the I register and so technically a new program designed explicitly to use it could make use of the I register for another purpose...

Aside from a character designer utility that shipped with the QS Character Board board, there were 6 commercial titles that I am aware of that supported it. It seemed a shame not to allow these original programs to be seen in their full UDG glory on real hardware, which is why I supported the format in Chroma. If anyone knows of any other original titles supporting the format then I'd be keen to hear about them.

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