[Amstrad CPC] core

[juri74]

not an issue but just a request:
could be possible to "unlock" 15khz RGBS mode please?
thanks

[renaudhelias]

Amstrad is using a 50Hz display, not interlaced. It cannot be scandoubler for mode 2 (lost of precision)

Using mist.ini scandoubler parameter, you can enable original signal output (SCART), but it was a blind development : some signal are ouput, but VSYNC/HSYNC offset are not confirmed.

I tested with my TV, but no way to run any 15kHz signals on it correctly (SNES doesn't run on it, same problem of display moving up), so I'm blind here. I have to validate a TV before validating my code...

Process generating TV signals is "aZRaEL_process" in
https://github.com/renaudhelias/CoreAmstrad/blob/master/BuildYourOwnZ80Computer/simple_GateArrayInterrupt.vhd
RED_out,GREEN_out, BLUE_out, HSYNC_out, VSYNC_out.

Another way of approach : compare signal with MAME's Amstrad core (if it does run correctly at 15kHz)

[juri74]

sorry for late reply,
i noticed other cores uses a RGBS (RGB + COMPOSITE sync) for 15khz video signal, maybe the problem is that HV sync control..
unfortunately VHD is alien language for me :(

[harbaum]

SCART TVs expect a composite sync. The VGAs vsync is connected the SCART pin used to detect a RGB signal and is constantly driven high. A TV will not cope with a video signal with separate H and V sync.

Bu tit's usually sufficient to xor hsync and vsync to get a csync acceptable for many TVs.

[juri74]

But it's usually sufficient to xor hsync and vsync to get a csync acceptable for many
TVs.

@renaudhelias maybe could you give it a try?
thanks

[renaudhelias]

Added to TODO-list
(TODO-list is here : http://www.cpcwiki.eu/index.php/FPGAmstrad#Effort_done)

[renaudhelias]

http://github.com/mist-devel/mist-board/tree/master/tutorials/soc#lesson-11-15khz-tv-video could be fine to adapt first (50Hz/60Hz), as it I could begin by... validating my TV.

@juri74 lesson11's core (60Hz with separate V and H sync) does run correctly on your TV ?)

[renaudhelias]

Hi @harbaum can you first align lesson11 60Hz 15kHz with unix "modeline" -parameters- command protocol ? (refactor) / "modeline" is an unix command showing all world screen/tv parameters for generating easily all world screen/tv signals...

[harbaum]

@renaudhelias thanks for the hint. I'll have a look.

[renaudhelias]

I saw in tutorial the use of xor for TV output, so then I try it at home, my TV sucks @15khz.

So I put a try by here : https://github.com/mist-devel/mist-binaries/tree/master/cores/amstrad/experimental

@juri74 perhaps you can try theses not-tested version (4 alternates).

[squidrpi]

@renaudhelias, if you point me to your source code changes for these 15khz tests I can have a look. I've done quite a lot of 15khz work recently and can test it properly.

[renaudhelias]

Amstrad is 50Hz

Candidate patchs are here (one is inversing the output signal...) :

• http://github.com/mist-devel/mist-binaries/blob/master/cores/amstrad/experimental/amstrad_170308_r005.8.14e_xorTV.txt
• http://github.com/mist-devel/mist-binaries/blob/master/cores/amstrad/experimental/amstrad_170308_r005.8.14e_xor2TV.txt
  Perhaps one between amstrad_170308_r005.8.14e_xorTV.rbf and amstrad_170308_r005.8.14e_xor2TV.rbf is running fine.

Component concerned is :
http://github.com/renaudhelias/CoreAmstrad/blob/master/BuildYourOwnZ80Computer/MiST_SCART.vhd
This MiST_SCART.vhd component does use the mist.ini feature http://github.com/mist-devel/mist-binaries/blob/master/cores/amstrad/experimental/mist.ini scandoubler_disable=1

Another component can be patched also :
http://github.com/renaudhelias/CoreAmstrad/blob/master/BuildYourOwnZ80Computer/simple_GateArrayInterrupt.vhd
My second patch is not a great one (xorTV2 and xor2TV2 alternative), I did just try hacking the "HSYNC_out" output (used for TV signal) by here
In this last component simple_GateArrayInterrupt.vhd you'll find the TV signal output generation :

• RED_out : out STD_LOGIC_VECTOR (5 downto 0);
• GREEN_out : out STD_LOGIC_VECTOR (5 downto 0);
• BLUE_out : out STD_LOGIC_VECTOR (5 downto 0);
• HSYNC_out : out STD_logic;
• VSYNC_out : out STD_logic

[renaudhelias]

If you never tryed CoreAmstrad all is explain here http://github.com/mist-devel/mist-board/wiki/CoreDocAmstrad#installation (you can contact me also : renaudhelias at gmail dot com)

[squidrpi]

Having a quick look this one looks correct to create the csync. I can't check properly until I get home and test the cores and see what signals are being generated.

See my quick conversion changes of TCA2600 here. Specifically:
VGA_HS <= not (vga_hsync_i xor vga_vsync_i) when tv15khz='1' else vga_hsync_i;
VGA_VS <= '1' when tv15khz='1' else vga_vsync_i;

[juri74]

hello @renaudhelias ,

my wife is at the hospital i do not have time to try at the moment sorry :(
i will publish your test link on my fb page and let other mist users to try it out.
thanks for your effort!!

EDIT 1: sony trinitron 21 inches (PAL TV but it support ntsc and pal60)
170308 r005.8.14e xorTv: image displayed with some disturbs & rolling up
170308 r005.8.14e xor tv 2: image displayed with some disturbs, off center on the left & rolling up
other two experimental cores: black screen

[renaudhelias]

amstrad_170308_r005.8.14e_xorTV will be integrated in next realise.
DrOG from atari-forum succeeded in running with it. I think last problem is about VSYNC/HSYNC signal length.

"Unfortunatley no F12-menu"

bernouilli from atari-forum did succeed also using amstrad_170308_r005.8.14e_xorTV, he said that amstrad_170308_r005.8.14e_xorTV2 is better centered (r005.8.14e_xorTV2 does correct a delay of RGB output versus HSYNC/VSYNC output, passing signal throw the same number of components, but it's a "no brain" version)
amstrad_170308_r005.8.14e_xorTV2 :

amstrad_170308_r005.8.14e_xorTV :

Offset seems needed, both in VSYNC and HSYNC.

[juri74]

great!

[renaudhelias]

amstrad_170323_r005.8.15c12.rbf published (for ones of atari-forum), normally does resolve OSD in TV mode. It's candidate 12 because I'm currently working on next version (FDC)

Return : OSD is OK.

[KLNHOMEALONE]

Please add AMX mouse support if possible

[renaudhelias]

amstrad_170328_r005.8.15c16e.rbf published "applying Gerald HSYNC/VSYNC width formula"

[renaudhelias]

@KLNHOMEALONE added to TODO-list (http://www.cpcwiki.eu/index.php/FPGAmstrad)

[renaudhelias]

"Perfect and well-centered!" - DrOG

[renaudhelias]

I've got a TV !
PAL 50Hz 15KHz Parrot test ( https://github.com/mist-devel/mist-board/blob/master/tutorials/soc/lesson11/lesson11.png ) does pass on it, but CoreAmstrad doesn't.
I'll refactor Parrot test into modeline and then in a second step will try to adapt it to CoreAmstrad output :)

[renaudhelias]

I compare HSYNC/VSYNC width with Parrot test, it results this experimental version : cores/amstrad/amstrad_170507_r005.8.14.2e.rbf (not tested)

[renaudhelias]

Ok, back from Tetalab laboratory.

r005.8.14.2e.rbf does run fine, one char or one half-char h-offset in left (screen not horizontally centered)

All chars are displayed, but HDISP does come too early and go away too later : about one half-char each.

Ignoring the two previous bugs. Border seems having a 4 chars size (H and V)

[renaudhelias]

amstrad_170507_r005.8.14.2j.rbf TV mode with borders (not tested)

[renaudhelias]

r005.8.14.2j OK for me, just an half-char offset of HDISP (cutting chars at right) but border limits OK.
Tryed also with another TV (same model but image not stable verticaly (blurred screen))

[renaudhelias]

r005.8.14.2 realized