The Sinclair QL Forum

Chr$ wrote:

Peter wrote: I can program them, but my stock of chips has become small. Would it be okay to re-program the chip you have?

This'll do it, right?

https://www.ebay.de/itm/LATTICE-ISPLSI1 ... 3533762297

If so, I don't mind buying it and getting it sent to you. I have to keep the original in its original state!

It might be quicker and easier within Germany while Derek is sorting out his programmer (and of course, with potential customs and nonsense for UK goods in a few days).

Edit: or this one, as I'm not sure if the E suffix to the 1016 above, is significant:

https://www.ebay.de/itm/1-Stuck-ISPLSI1 ... 2193767941

I just have to make the circuit board to programme the chips, which is a trival job, but time is short with all the Christmas eating and drinking, this made easier living in a less restrictive part if the UK.

The should be a trade deal with the EU & UK, but this should have any effect on shipping to the EU from UK. More than likely, the normal peop,e on both sides will pay for the travesty of the Brexit negiogations and final trade deal.

Sorry abou the rant...

Chr$ wrote:Could you supply this updated chip to me?

It should have arrived by now. You need to replace U23, which is the third PLD from left to right, if the power connector is in front of you. The one above the eight VRAM chips. Your monitor should then recognize a 1024x768 resolution and leave the lower third of the screen black. I have a 4:3 monitor with that exact native resolution, where it looks quite acceptable. The worst you can do is of course using a widescreen, changing the aspect ratio even more.

Peter wrote:

Chr$ wrote:Could you supply this updated chip to me?

It should have arrived by now. You need to replace U23, which is the third PLD from left to right, if the power connector is in front of you. The one above the eight VRAM chips. Your monitor should then recognize a 1024x768 resolution and leave the lower third of the screen black. I have a 4:3 monitor with that exact native resolution, where it looks quite acceptable. The worst you can do is of course using a widescreen, changing the aspect ratio even more.

Yes, got it yesterday, thanks Peter.

The monitor I use is an old 4:3 and I think it is a 1024x768. Will try it out.

Sorry for digging up such an old post. ***waiting for the backlash***

Having read through this entire thread, it seems that I have an issue that was not mentioned.
I have tried two monitors (a old Targa Visionary and a newer Samsung Syncmaster) with have the same problem.
In 512 x 256 mode, although the image is fine, the visible region is only 512 x 240.
In 1024 x 512 mode, some horizontal pixels are missing, making text hard to read, plus the visible region is only 1024 x 480.
The monitor reports 640 x 480 @ 72Hz, no matter what mode the Q40 is in.
This does not match the issues in this thread (that of black areas and a vertical frequency of 50Hz).

This is not a huge problem for me, I'm only using the Q40 as a test development platform and when it comes to doing the graphics, I shall simply limit the screen resolution.

However... if there is a simple solution to this (ie. someone has a replacement FPGA that will fix it), I am interested in purchasing one.

Nick

Nix wrote: ↑Wed Jan 17, 2024 1:04 pm
... if there is a simple solution to this...

I guess not then.

Hi,

I did wonder 20 years ago if signal conditioning the Q40/60 video signal from the board making a compatiable video signal for a modern monitor.

The Q40/60 display works perfectly on older CRT monitors, but the newer LCD/TFT monitors have limited video scan rates to suit PCs with AGP Video cards.

There has been reasonable results with video converters like OSSC, but even being open source, is very expensive. Maybe a cut down version of tbe OSSC could devised to suit the Q40/60.

Nix wrote: ↑Wed Jan 17, 2024 1:04 pm The monitor reports 640 x 480 @ 72Hz, no matter what mode the Q40 is in.

That's a typical problem with Q40/Q60 video output as there are (almost) no multisync flatscreens.

Nix wrote: ↑Wed Jan 17, 2024 1:04 pm This does not match the issues in this thread (that of black areas and a vertical frequency of 50Hz

That was with a replacment CPLD.

Nix wrote: ↑Wed Jan 17, 2024 1:04 pm However... if there is a simple solution to this (ie. someone has a replacement FPGA that will fix it), I am interested in purchasing one.

I can still program those CPLDs. The result will be 1024x768 signal but with black area.

Ah... I understand now. Thanks Peter.

I'll probably stick with what I have. It only affects me, for the time being.
Maybe in the future, if there are forum users that would like to have a play with my software and request the full size frame buffer.

Although... I'm now wondering about whether a Pi Zero is fast enough to read the VGA signal and display it, thereby converting it to HDMI

Nick

Nix wrote: ↑Sat Jan 20, 2024 11:38 pm I'll probably stick with what I have. It only affects me, for the time being.

Unfortunately it affects all Q40/Q60 users including myself.

Nix wrote: ↑Sat Jan 20, 2024 11:38 pm Although... I'm now wondering about whether a Pi Zero is fast enough to read the VGA signal and display it, thereby converting it to HDMI

Just converting it to HDMI works for me with a cheap off the shelf adaptor.
But HDMI flatscreens are not more "multisync" than VGA ones, so the root problem (wrong geometry detection) remains the same.

The Pi Zero has no realtime input interface that would be even remotely fast enough. The Pi Pico is closer. Oliver developed a Pi Pico converter for QL to VGA, but the throughput for Q40/Q60 needs to be 32 times higher. (Not to mention that neither Pi Zero nor Pi Pico have suitable ADCs.)

The Qzero could do the job if I add ADCs - but the result would be just like the OSSC. And I don't feel like months of work just to get the same thing neater and cheaper than the OSSC.

I have contemplated this issue for a decade and found no fully satisfying solution except a new Q60 video controller which directly supports 1024x768. (Such a design is so difficult that a new mainboard might be the better option.)

Peter wrote: ↑Sun Jan 21, 2024 10:40 am Just converting it to HDMI works for me with a cheap off the shelf adaptor.
But HDMI flatscreens are not more "multisync" than VGA ones, so the root problem (wrong geometry detection) remains the same.

Yes, the QL resolutions and weird pixel aspect have always been a bit odd.

Peter wrote: ↑Sun Jan 21, 2024 10:40 am The Pi Zero has no realtime input interface that would be even remotely fast enough. The Pi Pico is closer. Oliver developed a Pi Pico converter for QL to VGA, but the throughput for Q40/Q60 needs to be 32 times higher. (Not to mention that neither Pi Zero nor Pi Pico have suitable ADCs.)

It was just a glib, off the cuff idea without any real thought. I'd forgotten that the Pi doesn't have ADC.
The idea was somewhat fanciful, wondering if the Pi could read the analogue video data and then, real time, interpolation onto the display at whatever resolution was selected.
Probably way too much compute power than the Pi can deliver.
1024x768 might not be too bad with a bit of a cheat. Taking every two horizontal scan lines from the Q40 and interpolating a third to sandwich in between in order to create 3 scan lines on the output. Relatively simple maths, two right shifts and an add to create the interpolated pixel in between. Not accurate, but probably good enough. Still way beyond the capabilities of a Pi. Sample rates of around 30MHz. Doable with dedicated hardware maybe. I don't know, not my area.

Sorry... rambling