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goron59
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Joined: 24/03/2019
Location: United Kingdom
Posts: 4

Posted: 03:12am 09 Apr 2019

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Hello, new forum member here.

I recently acquired a CGCOLORMAX2 from CircuitGizmos and generally pleased with it, but it has an annoying problem with horizontal positioning of the RGB/VGA output.

On both my LCD panels with VGA input, the display is clipped on the left side by about 4 or 5 pixels.

On one of the displays, I can go into its control panel and adjust the Horizontal start point (along with H scaling) and all is good, but on my main display I cannot.

Is there something that can be done on the board itself to change this?

Another quirk I've noticed that if you switch to a lower resolution mode (mode 4), the display becomes quite noisy/blurry and stays that way when returning to modes 1 through 3.

Thanks

goron59
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Joined: 24/03/2019
Location: United Kingdom
Posts: 4

Posted: 03:22am 09 Apr 2019

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Ha, just after posting this, I see see page: http://geoffg.net/MaximiteFAQ.html

And

Quote The left hand character of each line is missing. This only happened after I upgraded my Altronics kit to the latest version of MMBasic.

This is easy. At version 2.6 the timing of the VGA output was altered slightly to correct another issue. This had the effect of shifting the entire screen left by eight pixels compared to earlier versions. To fix your problem all you need to do is adjust the horizontal positioning on your monitor to bring the missing pixels back into view.

So I'm probably doomed then unless I use my other screen :/

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 04:46am 09 Apr 2019

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You should be able to adjust your monitor. The timing of the Colour Maximite's VGA is not perfect but it is close enough that I have always been able to get a good image.

I am not sure what is happening with your mode 4 fuzziness - I have never seen or heard of that before.

Geoff

Geoff Graham - http://geoffg.net

tomxp411
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Joined: 04/04/2019
Location: United States
Posts: 24

Posted: 05:07pm 09 Apr 2019

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Geoffg said You should be able to adjust your monitor. The timing of the Colour Maximite's VGA is not perfect but it is close enough that I have always been able to get a good image.

I am not sure what is happening with your mode 4 fuzziness - I have never seen or heard of that before.

Geoff

It happens to me, too. When I switch to Mode 4, then back to 3, the colors don't quite line up... so all of the text has a fringe of color on the left side.

On the timing thing... I'm planning on rebuilding the firmware anyway, to port in some BASIC 5 functions. If you could indicate which module has the timing information, I might try tweaking it to see what happens.

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 10:01am 10 Apr 2019

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tomxp411 said If you could indicate which module has the timing information, I might try tweaking it to see what happens.

I don't provide support for recompiling the source but that one is easy: Video.c (obviously).
I admire your confidence, especially as you have not yet looked at the code.

Geoff Graham - http://geoffg.net

goron59
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Joined: 24/03/2019
Location: United Kingdom
Posts: 4

Posted: 11:42am 10 Apr 2019

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Thanks for the messages guys.

Geoff, I hear you on using the monitor to adjust the H position.
I've now tried it on four different panels and all have the problem and only one is adjustable, so getting a new one that will work for me is on fairly short odds. Sadly the panel where it does work is serving TV duties in my guest room.

Colour fuzziness seems to be quite common when doing RGB output which is then interpreted by non CRT display tech... so I'm not _that_ bothered about it. mode 4 isn't something I'd ever use anyway.

The Video.c code does indeed look a bit hairy, but fundamentally a bunch of parameters that could be tweaked/ stored in flash rom (GetFlashOption(... ) and OPTION VGA PARAM xxx maybe) ?

A quick scan and VGA_HSYNC_T looks interesting as does the P_VID_OC_OPEN macro where it's used.

Just a thought. Would be nice to have some flexibility here, or maybe I should just get a CRT monitor :)

tomxp411
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Joined: 04/04/2019
Location: United States
Posts: 24

Posted: 05:29pm 10 Apr 2019

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Geoffg said

tomxp411 said If you could indicate which module has the timing information, I might try tweaking it to see what happens.

I don't provide support for recompiling the source but that one is easy: Video.c (obviously).
I admire your confidence, especially as you have not yet looked at the code.

It seems straightforward enough, and I think I see why this is happening. And I also don't see an easy fix. If you add another byte of padding to the output buffer, that just shifts the entire screen to the right by 1.5 text columns.

What happens if you change VGA_LINE_T a little bit to make the pixel clock a little bit faster? I'm thinking that would make the line a little shorter, and an extra bye of padding wouldn't cause it to overrun the right side of the display.

goron59
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Joined: 24/03/2019
Location: United Kingdom
Posts: 4

Posted: 06:22pm 10 Apr 2019

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Having the display start and stop within normal H bounds for a VGA compatible panel without clipping is pretty useful I think. Altering the timing so the display is slightly narrower is acceptable. The borders are quite big anyway.

As I posted above, the whole thing is driven by half a dozen or so params, so making them adjustable from OPTION keywords in BASIC would be ideal.

Even if they were canned to OPTION VIDEO VGA2 I'd be happy!

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