Sinclair ZX80 / ZX81 / Z88 Forums

I've updated the link above and hopefully it now works...

olofsen wrote:I've updated the link above and hopefully it now works...

I tried the new version out and it is working correctly now.

siggi wrote:Here my first results:
OUTLAW.P (Dr. Beep): stable picture, but some stable distortions at the top of screen
SPONZY-ROM: stable picture
Nuclear invaders (NUCINV16): unstable
Microman (full WRX): unstable
Pacman: unstable
HRDEMO30: unstable
DSTAR (old fullscreen WRX-Version without sound): unstable

So most hires programms are not shown stable on my Led-TV/CHROMA81

HTH Siggi

I've tested these programs with a Chroma interface and they worked fine for me. So I connected an oscilloscope to the synchronisation signal from the SCART socket and looked to see if there were any additional pulses that might be upsetting your TV but I did not find any. I also checked the timing between pulses and the duration of the sync pulses but didn't notice anything odd here either. It sounds like your TV might be very sensitive to timings of the sync signals being output by the ZX81.

Is this still available? In the USA? I would need conversion to A/V from SCART,

Thanks

Tim

Well - I think so.
Look here:
http://www.fruitcake.plus.com/Sinclair/ ... bility.htm

tdg8934 wrote:Is this still available? In the USA? I would need conversion to A/V from SCART

Hi Tim, yes I still have the Chroma interface available. It does supports the ZX81 running at 60Hz (NTSC) but it only outputs a RGB SCART picture. You can't just use a basic SCART to A/V converter since this only maps the SCART pins to A/V connectors. You would need a device that intelligently converts the video format.

Unfortunately I don't know of one that I can recommend to you. Maybe other forum readers can recommend a suitable device?

If you require more details on the Chroma interface then feel free to contact me via my website (the link given in the previous post).

Paul,

I have been out to your site and this device is really cool!

I would like to get a quote on ordering a Chroma device (keep in mind I do have a ZXPAND and AY sound plugin board). Let me know what the shipping cost is for other items as well such as your RS-232 cable, ZXC4 eprom card, and anything else I missed that would be helpful for my TS1000 (for use in the USA). I live in Mundelein, Illinois with a zip code of 60060 if that is required to calculate shipping costs. I am using an adjustable 3-12v 1A wall transformer for TS1000 power (set to 7.5vdc). Hopefully that's enough power with 1A. I am currently also using a KWorld USB device to convert composite video from my TS1000 to USB into my laptop and then I run a generic program WebCamViewer v1.0 that finds the video input (WDB2860 Capture) and displays the TS1000 in a window nicely on my laptop running Windows 10. I don't have any RS-232 ports so I'll need a USB to RS-232 converter and crossover cable. I also have an HDMI connector (not sure if that is an input or output?) on my laptop so perhaps an SCART to HDMI converter if anything exists (if not I can probably find an SCART to A/V one online) - Recommendations anyone?

Let me know what you have to sell to me with costs and shipping and what I will need to get elsewhere.

Thank you,

Tim Gilmore

tdg8934 wrote:I also have an HDMI connector (not sure if that is an input or output?) on my laptop so perhaps an SCART to HDMI converter if anything exists (if not I can probably find an SCART to A/V one online) - Recommendations anyone?

Hi Tim

I suspect the HDMI connector on your laptop is output only.

About video signals:

In the analogue days, first there was monochrome (black and white) TV. Due to the way the electronics worked, the scanning of the screen was linked to the mains frequency. Hence 60Hz in some of the world and 50Hz in the rest of the world.

Then colour was developed. Each country decided on a colour TV standard, so we ended up with at least three main colour standards in addition to the two frequency standards...

With-in this the way of encoding the colour video signal so it can travel has has different standards:-

In the CRT TV's, the bit of circuitry that drives the tube needs a Red, Green and Blue channel. So in Europe a French connection standard (now known as SCART) came about, this allowed for two different types of video signal. One of which is RGB video. For computer displays, this is the best analogue signal standard.

But this is no good for using over long distance links. So a more complex form of encoding was used. This is known as composite video. All the monochrome, colour information and synchronization signals are combined into one very complex signal. And the signal is different for each frequency system and each different colour system (although not all combinations are used). The SCART standard can also carry a composite signal.

To convert a RGB signal to a composite signal needs some complex electronics. So if you want to use a RGB system to "talk" to your KWorld USB device, you will need a converter to convert RGB to composite video.

Mark

Hi Tim

I've sent over details of the Chroma interface to you.

Regards

Paul

I've recently updated my ZX ROM Cartridge Creator to support the generation of multi-program ZX81 compilations for use with my ZXC ROM cartridges (which were originally developed for use with the ZX Spectrum fitted with a ZX Interface 2). A compilation can contain up to 254 ROM (.bin) and program (.p) files. A menu is automatically produced for the programs added and will appear whenever the ZX81 is powered on or reset to allow selection of the program to run.

The Cartridge Creator includes support for the Chroma interface's colour and QS Character Board emulation facilities. Colours can be applied to existing games without the need to modify the game in any way. Likewise, alternate character set bit patterns can be defined and the game displayed using these. The colour and character graphics are defined in simple text files which can be loaded into the Cartridge Creator and assigned against each ZX81 program. The menu system will present options to run such games with or without the colour and / or character data applied.

Once a compilation has been assembled, it is ready for transmission to the ZX81 via a serial cable to the Chroma interface's RS232 socket. The ZX81 receives the data at a baud rate of 57600, erases the cartridge and then programs the new compilation data into it.

The Cartridge Creator supports ZX81 compilations for the ZXC2, ZXC3 and ZXC4 (note that the ZXC2 is only programmable using an EPROM programmer). The ZXC2 and ZXC3 are no longer available, but the 4MB ZXC4 is still available and can be used with either the ZX81 or the Spectrum.

Note that ZXC4s sold for use with the Spectrum prior to July 2015 require an upgrade before they can also be used with the ZX81. If you have an existing ZXC4 that you wish to use with a ZX81 and Chroma interface then please contact me through my website to arrange an upgrade to the ZXC4.