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