QL-VGA, the second

By | 2020-01-08

The last few weeks I continued working on the QL-VGA adapter, for once to have one myself and also because I was pretty strongly petitioned by some people. I’m not an electronics guy by trade, so this is some tough order for me. The first PCB I ordered looked gorgeous, but it was already obsolete by the time it arrived from China, in my haste I had made too many errors. I ordered the revised PCB on new years eve and a week later this happened:

I decided to stay with the readily available Cyclone II development board as it already contains pretty much all components like voltage regulators, FPGA chip, bootstrap EEPROM and some more stuff and it’s actually cheaper to get than just the chip on its own ๐Ÿ˜ฎ

Of course the Cyclone II is downright overpowered for the task, it’s only utilized about 10%, but changing chip would be quite a huge task for basically no benefit other than the fact that having a single board solution would be a little bit more elegant in my eyes.

Anyway, my own board just adds the RGB input with level shifter, VGA output and SRAM chip. All the magic happens in the FPGA code, which is why I like FPGAs more and more, it empowers software people like me to solve real hardware problems ๐Ÿ™‚ I designed the board upside down, so it forms sort of a compact sandwich with the FPGA base board (and as a fun exercise I decided to design the board single sided, there is not one trace on the visible side):

This time the SRAM is fast enough to allow for MODE 8, so this version is fully QL compatible and perfectly matches the 512×256 pixels to a 1024x768x60 VGA screen. The resulting signal in turn is easy to convert to HDMI, I got myself a 5โ‚ฌ converter which works perfectly:

In theory the board could also be connected to a ZX Spectrum 128 as this has a very similar RGB output to the QL, but I did not bother develop any FPGA code for this yet. Also, the QL code is currently PAL only, no provisions for NTFS NTSC have been made.

So what now?

Quite frankly, I’m not sure. This thing needs to be tested a lot more first, and then maybe there might be a production run. But actually shipping packages and stuff is not an activity I particularly enjoy, so I’ll see how I could handle this. But anyway, let me know what you think of my little project (comment, eMail, Facebook, whatever).

Forum thread

24 thoughts on “QL-VGA, the second

  1. Fabrizio Diversi

    Thank you Marcel, another step forward….any chance to have one? -)
    Ciao
    Fabrizio

    Reply
  2. pjw

    had this been available a couple of years ago i would have kept my faithful old ql! good job, marcel!

    Reply
  3. Martyn Hill

    Another truly valuable project, Marcel! Thank you!

    Should you get around to producing a batch for sale, please put me down for a few!

    Reply
    1. Adam

      Maybe get amazon to fulfill the orders for you. Makes it easy for buyers and you, although it will understandably push the price up.

      Reply
      1. Marcel Post author

        You need to invest thousands of Euros to get a product up to a certification level that allows you to sell it on a major platform without fear of legal hassle.

        Reply
  4. Urs

    Great project. I like the design decision to use a widely-available cheap platform. Lokking forward to see this this become available for the QL community. Seeking for testers? I would jump in with my various QLs and multiple VGA monitors.

    Reply
  5. tofro

    Supposed it can display more than vertical stripes ๐Ÿ˜‰ I want one or two.

    Reply
  6. Charles Ingley

    Great project! Like the single-sided PCB (and FPGA’s rule – only things we could dream about can be done now ๐Ÿ™‚

    Reply
  7. Marco Banchero

    Hi Marcel
    It looks a very nice project. Most of all a useful and practical solution. I would like to have one or two if you decide for production of some of these.

    Reply
  8. David Westbury

    Nice ๐Ÿ™‚

    Cyclone II with a QL display ‘shield’

    Reply
  9. Ralf R.

    Also nice to see the font of “QL-VGA” ๐Ÿ˜‰

    Reply
    1. Marcel Post author

      Well spotted ๐Ÿ˜‰ Same font kicks in as a screensaver when no input signal is detected.

      Reply
  10. Peta

    Hi Marcel, great work indeed. I do not need it, since I am using QPC only, but I suggest you sell all boards to a distributor and you let them do the packaging and managing all the selling details.
    regards Peta.

    Reply
  11. Mathias

    Thank You Marcel for a great device (again)! Happy to get my QL-VGA at 24th ZX Team Meeting at the end of March ๐Ÿ™‚

    Reply
  12. Frank Mariรซn

    Wow Marcel,

    (Just read about QL-VGA in QUANTA Magazine)

    I’ve been walking around with a vague idea about something like this for a while, only came as far as staring at both QL-RGB and VGA signals on the scope and wondering what the easiest way would be, and calculating ratios.. Excited that you’ve actually gone and done it!

    Definitely interested in this project, both in terms of design, possibly assisting any way I can, and obviously buying a few off you should you get to that stage. I’d be fine with anything from just-the-Eagle-files-and-BOM all the way up to a finished product. As long and I can get my hands on one ๐Ÿ˜‰

    Also, FYI: My favourite PCB house has a German branch, they may be more helpful (and easier to work with, and faster) than the Chinese ones. They have strong online pre-production checks.

    https://www.eurocircuits.com/

    They also have an assembly facility, it may be an option to handle production runs if you don’t want to be doing/organising those.

    Good show, sir! If there’s anything I can do to help, tell me!

    Reply
    1. Marcel Post author

      Hi Frank!

      Thanks for the kind words! It’s probably best if we continue this via eMail, I’ll send you one.

      Cheers, Marcel

      Reply
  13. Charlie

    I would like a solution like this. I hope things continue to go well.

    Reply
  14. Joe

    Excellent project – exactly what I would buy right now! How can I help?

    Reply
    1. Marcel Post author

      Hey Joe, thanks! Basically I did a production run of 30 boards but then Corona happened and anyway, distribution is time intensive and there were so many other things to do. But shipping will start eventually…

      Reply
  15. Joe

    no worries – if you think of anything, I will do what I can to help.

    Reply

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