Pico TTL2DVI - MDA/HGC/CGA/... to HDMI Converter \ VOGONS

Pico TTL2DVI - MDA/HGC/CGA/... to HDMI Converter

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First post, by charlysan

Posted on 2026-08-07, 15:25

charlysan Offline

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I have been experimenting with this cheap Waveshare RP2350 board, which includes a DVI port. Inspired by rgb2hdmi, I have been able to put together some firmware and a basic circuit to capture TTL video and output it over HDMI, with pretty good results.

So far, I've tested it with HGC, CGA, and Commodore 128. Multiple parameters can be configured using the serial console, as explained in the README file. There is no EGA implementation at the moment (because I don't have any card in good shape), but I plan to include it soon.

I might also add some basic DIP and SMD PCB designs in the future.

I shared the project in GitHub:
https://github.com/charlysan/pico-ttl2dvi

Reply 1 of 6, by keenmaster486

Posted on 2026-08-07, 17:33

keenmaster486 Offline

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Very cool. I've been hoping someone would do something like this.

How far can you go with input vs. output resolutions? Is VGA from the feature connector a possibility?

World's foremost 486 enjoyer.

Reply 2 of 6, by charlysan

Posted on 2026-08-07, 19:08

charlysan Offline

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keenmaster486 wrote on 2026-08-07, 17:33:

Very cool. I've been hoping someone would do something like this.

How far can you go with input vs. output resolutions? Is VGA from the feature connector a possibility?

PicoDVI is tied to sysclk. 800x600 would need ~400MHz sysclk. RP2350 is specified at 150MHz, and we are already overclocking to 260MHz here. Using HSTX might give us more room, (but it can't be done with this board and builtin dvi connector). Using Adafruit Feather RP2350 with HSTX Port might be an option. But, do we really need to go that far for this retro TTL video use case?

I didn't understand your question related to VGA. Are you talking about DE15 connector?

Reply 3 of 6, by wbahnassi

Posted on 2026-08-07, 19:11

wbahnassi Offline

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Nice device, it cries for CRT effects though... at least scanlines.

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Reply 4 of 6, by keenmaster486

Posted on 2026-08-07, 19:15

keenmaster486 Offline

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Honestly, 800x600 is not really necessary, I'm thinking of 400 and 480 line modes. The big problem to solve with VGA is near-instant transition between 720x400 text mode and 640x400, 320x200 (line doubled), or 640x480 graphics modes, without requiring adjustment after a mode change to fix the sampling alignment and restore uniform pixel sizes. This is also a problem with EGA, as there are two EGA modes, 200 lines and 350 lines, but those do have the same horizontal pixel count (320/640).

The feature connector is an internal pinout on VGA cards that exposes pre-RAMDAC digital video out - not sure if it's exactly the same as TTL from an EGA card, but it has RGB and H/V sync iirc.

World's foremost 486 enjoyer.

Reply 5 of 6, by charlysan

Posted on 2026-08-07, 19:32

charlysan Offline

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wbahnassi wrote on 2026-08-07, 19:11:

Nice device, it cries for CRT effects though... at least scanlines.

Yes. Already tried scanlines emulation in MDA mode (although not implemented in the right way, it was just a quick test). I will include the feature in next revision. But not sure if it will be straight forward for all the modes.

Reply 6 of 6, by charlysan

Posted on 2026-08-07, 19:35

charlysan Offline

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keenmaster486 wrote on 2026-08-07, 19:15:

Honestly, 800x600 is not really necessary, I'm thinking of 400 and 480 line modes. The big problem to solve with VGA is near-instant transition between 720x400 text mode and 640x400, 320x200 (line doubled), or 640x480 graphics modes, without requiring adjustment after a mode change to fix the sampling alignment and restore uniform pixel sizes. This is also a problem with EGA, as there are two EGA modes, 200 lines and 350 lines, but those do have the same horizontal pixel count (320/640).

The feature connector is an internal pinout on VGA cards that exposes pre-RAMDAC digital video out - not sure if it's exactly the same as TTL from an EGA card, but it has RGB and H/V sync iirc.

Oh, that edge connector. Interesting...

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