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Author Topic: External colour tests (Read 1304 times)

Online gflorez

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External colour tests
« on: 2018.June.03. 19:25:08 »
Yesterday I attended a closed doors retro-computer convention. It was a reunion of Retrowiki members on Navia, near Oviedo at north of Spain, just at the Cantabrian sea, about 500Km from Madrid.

Of course I was the only assistant who carried Enterprises, not the others fault, as it is considered a very complete computer, but it was scarcely sold on our country. On the other side, most members of the Spanish website are interested in more than one computer model, not like me....

There was a variety of micro-computers displayed, from  Spectrums on all their many incarnations(even Timex-Sinclair),  to Amstrads CPC PCW CPC+, Oric, MSX, Amiga, Atari, Mac, Silicon Graphics, Raspbwrry-pi, and a lot more that I can't remember now.

But the main intention of the annual reunion is to present, debug and develop new gadgets for the computers, like memory, SD adapters and other peripherals.

I brought my humble contribution, the bus expander and the M-Slot prototype. One of my friends, Dandare, showed a preliminary version of the Dandanator for CPC, that consist on a cheap card(less than 15 Euro) with 512KB FlashRom, able to hold 10-15 games. It is able to load a game instantaneously, and save/load its progress. Nearly 1500 Dandanators for Spectrum have been created up-to-date. Another friend, Habi, presented a card that provides colour and sound to the Amstrad PCW(a silent, only green phosphor monitor CP/M computer, intended only for business).

Talking with Habi  about how a FPGA interprets the colour of the only green screen, the conversation turned to how the microcomputers of that era codified the colour, halving the resolution when doubling the colours. This though lead us to how clever is the design of the LPT table on the Enterprise. Habi himself owns an Enterprise, and asked me how the colour inputs on the expansion connector works. I answered what I know about the tests made by Balaguesz. Then he said so quiet: "what if we try to do the same with my 20 euro FPGA? I can take advantage of the already written core for the PCW."

I showed him the Nick description document on Zozo's page an he read it briefly.

The main problem interfacing FPGAs with retro-computers is that they work on 3.3v, but fortunately he has a bridge card that makes the signal conversion.  He gave me some Dupont cables and asked me to connect the required signals to the rear connector of my bus expander.

He needed:

-14MHz clock
-Horizontal and Vertical synchronisms
-Ground only, as the FPGA has its own power supply
-EC0 to EC3
-/EXTC

After a few problems with the Dupont cables connection, soon we had reception of the output signals on the FPGA. Then he made some corrections on the code and tried to compile it. Take in account that the code of a FPGA describes how the real hardware is emulated inside, so it has some strict rules that must be observed. It took about 2 minutes to completely compile the code. But we repeated the procedure several times, because at first time it didn't work as expected. Soon he discovered the real resolution of the Enterprise, did some corrections and after only one hour trying we started to see the effects on the screen.

21242-0

21244-1

21246-2

There is some noise on the injected data, probably due to the proximity of other retro-computers.


Offline Zozosoft

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Re: External colour tests
« Reply #1 on: 2018.June.03. 19:48:48 »
There is some noise on the injected data,
It is also can be due the wire lenght. Look the schematic of the original expansion board. The video signals only connected to the first slot which is closer to the machine. (Probably due same reason the audio inputs only at the first two slots.)

Online gflorez

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Re: External colour tests
« Reply #2 on: 2018.June.03. 20:29:20 »
As always you are right... 

My friend says that it can be very easy to make an expansion card to attach the cheap FPGA. It has a lot of memory and two long headers of all configurable input/output pins.  Imagine the new projects that could be made with it....

Offline geco

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Re: External colour tests
« Reply #3 on: 2018.June.03. 22:18:12 »
As i see what you did is similar to 1st tests by Balagesz :-) , it is very impressive that it was made within some hours. A very good sprite card could be done, éven a full screen could be displayed with it with 2 color resolution with 16 colors.

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Re: External colour tests
« Reply #4 on: 2018.June.04. 09:31:28 »
Yes the SymbOS screen has 4 colours, but the injected signal has 16 colours at full resolution. The limitation is, the signal can only be injected on displayed zones, not on border zones.

The next weekend he will try to digitalise a graphic to play with it. But then  I need to explain him how the first eight colours of the palette are organised, and how to change the other eight byas colours.

I remember  a chart of colours on some thread.

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Re: External colour tests
« Reply #5 on: 2018.June.04. 10:25:20 »
And there will be other limitation, colors for external color input are defined by LPT.

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Re: External colour tests
« Reply #6 on: 2018.June.04. 10:58:32 »
Yes, but that is because in the experiment the FPGA is autonomous, its task is very easy, it only admits synchronisms and returns the colours bits and /EXTC. This takes very little of the complete possibilities of this FPGA, not so big as the MIST, but at the side with the ZX-ONE. You can put inside a complete computer, so we can define the needed ROM and RAM segments and communicate the module with the Enterprise buses to take total control. You can, for example, define one or two AY sound chips, like in the other Balagesz project, and inject the output to the Enterprise sound inputs....  It is incredible but possible. We only have to learn how.

Offline Tutus

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Re: External colour tests
« Reply #7 on: 2018.June.04. 11:43:28 »
This is very promising!
At last someone seriously deals with developments ...

:smt038 :smt038 :smt038

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Re: External colour tests
« Reply #8 on: 2018.June.04. 18:34:27 »
I want a colour chart to show to my friend Habi. Can some one give me a link?

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Re: External colour tests
« Reply #9 on: 2018.June.04. 18:35:20 »
I want a colour chart to show to my friend Habi. Can some one give me a link?
http://ep.lgb.hu/colors.html

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Re: External colour tests
« Reply #10 on: 2018.June.04. 21:56:16 »
Thanks!

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Re: External colour tests
« Reply #11 on: 2018.June.05. 00:09:11 »
Habi said:

"I do not think the noise is due to the length of the cables. Probably the color input pins where only in the first slot because only one expansion should access those signals; more than one would make a short."

Later he realised the real cause:

"The noise on the signal is due to wrongly injecting the pixel on the opposite flank. This makes unstable the colour border".
« Last Edit: 2018.June.05. 10:23:13 by gflorez »

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Re: External colour tests
« Reply #12 on: 2018.June.06. 20:40:51 »
With the Balagesz test hw we got nice stable picture, there is a example of full resolution graphics (Istvanv made the pic with epimgconv)
http://enterprise.iko.hu/video/DSCF7972.AVI

Other possible problem: which Nick chip used?
I discovered during the testing, the 08-04 Nick problems still present with external colors :-( Then it is somewhere at the color outputs...
Example on one of worst machines:
http://enterprise.iko.hu/video/DSCF7929.AVI

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Re: External colour tests
« Reply #13 on: 2018.June.07. 11:49:30 »
http://enterprise.iko.hu/video/DSCF7972.AVI
http://enterprise.iko.hu/video/DSCF7929.AVI
You can embedd the videos on your site. Upload the videos to the Youtube, get the code there under the video and put the code into the html of your site. It looks smarter.
---
Egyszerűen meg lehet csinálni, hogy a videókat az oldalon meg lehessen nézni. Feltöltöd a videót a Youtube-ra, ott a videó alatt van pár opció, ott ki lehet választani a beágyazást. Onnan ki kell másolni a kódot és az oldalad html-jébe betenni, így már az oldaladról megnézhető a videó.

Online gflorez

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Re: External colour tests
« Reply #14 on: 2018.June.07. 19:04:02 »
You are right, the first test where made on my old EP that has a defective Nick. But Habi claims to have fixed the noise on his Enterprise at his home, so I don't know what to think...

Meanwhile I have ordered one of these FPGAs to replicate the tests. I have to learn fast.