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 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 😮

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 🙂 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 5€ 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

11 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
  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 😉 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 🙂

    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 🙂

    Cyclone II with a QL display ‘shield’

    Reply

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