ZX80 Core - new ZX80 motherboards

[PokeMon]

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The LED control mechanism can influence brightness of all 3 colors (red, green, blue) separate with pulse width modulation. The LEDs are driven with 20mA current independent of the used voltage (9-12V) and the brightness is simply controlled with PWM. I wandted to use a specfic IC for it (LTC6992) but changed it after because I didn't check the cost of it very well, which is about 4 EUR and is needed 3 times. I replaced it with a specific transistor which has a suitable pin out to use on the layout now. The transistor is placed a bit unusual as shown here in the picture:

IMG_6705sk.JPG (145.09 KiB) Viewed 4828 times

[PokeMon]

It is quite difficult to reproduce the color effects with a digital still camera or video camera because self shining sources are difficult to catch and overframe the picture. I tried to catch the lightning atmosphere.

The LEDs are controlled with following signals:

RED - signal /RAMCS (shows ratio of RAM and ROM access)
GREEN - signal video pixel (shows ration of white and black pixels)
BLUE - signale /KEYBD (shows quantity and duration of keyboard read attempts)

This will give following colors for ZX80 / ZX81 activities:

GREEN after switch on / in input or program mode. Changes with increasing blue color to yellow when screen is filled more and more.

IKIT-Screen-Emptyk.jpg (166.03 KiB) Viewed 4828 times

BLUE will shine as soon as a program is started with RUN till it is stopped. There are long periods of keyboard reading as this signal sets a flipflop and stays until the flipflop is reset by a OUT $FF,A which will not be used in BASIC programs.

IKIT-Runningk.jpg (161.81 KiB) Viewed 4828 times

VIOLET during LOAD or SAVE

IKIT-LOADk.jpg (135.09 KiB) Viewed 4828 times

[PokeMon]

RED during SAVE when data is sent. So first a period of VIOLET for 5 seconds and after the color changes to RED.

IKIT-SAVEk.jpg (136.21 KiB) Viewed 4827 times

And here an example with a filled screen and many set pixels, the color changes depending on the screen content from GREEN to YELLOW.

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I offer this KIT (all needed parts) for self assembling/soldering for about GBP 4.00 plus shipment GBP 1.50. If someone interested here, please write me a PN.

Here the schematic:

IKIT-schematic.jpg (36.24 KiB) Viewed 4827 times

[PokeMon]

And here a Youtube video with LEDs in action.

http://www.youtube.com/watch?v=Yc96vlH399w

[Rink]

That is f'in disco!!! Cool.

[PokeMon]

So here the more conservative version.

On your choice with either one or two LEDs.
You can choose LEDs of your favourite color.
The LEDs are supplied with the 9-12V input from power supply and do not increase the load of the power regulator.

The protecting resistor shoud be about 1k for normal LEDs and can be placed best way as SMD (0805 or 1206) on bottom side / soldering side.
The value of the resistor can be higher for low power LEDs. Blue color LEDs have a higher voltage drop and can be used with smaller resistor values and depending on the desired brightness. So with 1k you can expect about 7 to 10 mA with one LED or 5 to 7 mA for two LEDs in series.

Important: the polarity of the LEDs (longer pin) have to be assured like shown in the pictures above.


For use with one LED only:

SingleLEDkx.jpg (210.07 KiB) Viewed 4796 times

For use with two LEDs:

DoubleLEDkx.jpg (188.65 KiB) Viewed 4796 times

[PokeMon]

So the documentation was updated with the new module ZX80IKIT and appendix A4 for troubleshooting with some oscilloscope pictures to measure.

http://www.8bit-wiki.de/index.php?id=3& ... 7ad2d90000

[retrolab]

Hello.
My new ZX80Core is working!!!! I'm very happy!!! All the guide instruccions have been very useful and clear and all is fine.
Thanks, PokeMon.

[PokeMon]

Nice to hear.

[Kiwisek]

All the guide instruccions have been very useful and clear and all is fine.

I have to say the same. Congratulations to the very nice guide! Not many people today can do such easy to understand guide for beginners. Good job!

Btw. I placed Louis Seidelman's RAM test for download to my blog http://www.8bity.cz/2013/sinclair-zx80-ram-test/. Sorry for the language, you can try autotranslate in the upper right corner and the link for download is near the end of the artcile before the blue screenshots