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raspberrypi / pico-extras

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Schematic or hardware specification for scanvideo.c ? #63

Closed Andy2No closed 1 year ago

Andy2No commented 1 year ago

I see the VGA generator is based on 5:5:5 RGB pixels, but I don't see any details of the video DAC used, or a schematic for one. I assume a resistor based DAC is intended? If so, what resistor values are suitable?

Do the hsync and vsync signals also need resistors? Is there any other circuitry needed besides just resistors?

A simple schematic would be useful. Failing that, just a clear description of how to build it.

On first look, I don't even see how the GPIO pins are assigned, or any obvious documentation about that. I'd presumably need to wade through the code to try to figure it out. A simple table of pin assignments would be a good start.

JamesH65 commented 1 year ago

I believe the schematic on this page is the relevant one? https://github.com/raspberrypi/pico-playground which refers to the reference design in here https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf

Andy2No commented 1 year ago

Thanks @JamesH65

It would be good if someone could add that link to the documentation, maybe in the readme files at: https://github.com/raspberrypi/pico-extras/tree/master/src/common/pico_scanvideo

and / or https://github.com/raspberrypi/pico-extras

JamesH65 commented 1 year ago

I've made some changes, the PR is linked just above. Would that be adequate?

lurch commented 1 year ago

I believe the schematic on this page is the relevant one? https://github.com/raspberrypi/pico-playground

See also https://github.com/raspberrypi/pico-playground/issues/20 :confused:

Andy2No commented 1 year ago

Thanks, @JamesH65 and @lurch

Yes, the PDF seems like the best thing to link to, and just linking to it from the https://github.com/raspberrypi/pico-extras readme is probably enough. That's one of the places I looked, when I was trying to figure it out.

I'd be inclined to add it to the readme for each part of pico-extras where it's relevant too, and maybe add a comment to the main .c files, but maybe that's overkill.

JamesH65 commented 1 year ago

Change ha been merged so closing.

JamesH65 commented 1 year ago

@kilograham Don't appear to be able to close issues on this tracker, but this one is OK to close.