Sidequest: VGA scan doubler

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Smonson
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Re: Sidequest: VGA scan doubler

Post by Smonson »

exxos wrote: Thu Dec 31, 2020 2:39 pm If you look at the first image I posted the colours show how its wired..
Aha, right, I see what you mean. Sync looks good in your photos. It's only blank that needs to be disconnected. If you can't disconnect blank on the H5 then it will probably at least work for monochrome.
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exxos
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Re: Sidequest: VGA scan doubler

Post by exxos »

Smonson wrote: Thu Dec 31, 2020 2:47 pm Aha, right, I see what you mean. Sync looks good in your photos. It's only blank that needs to be disconnected. If you can't disconnect blank on the H5 then it will probably at least work for monochrome.
I tried disconnecting the blanking to the DAC IC, makes no odds.. if I remove the buffer blanking it just goes like this...

IMG_5922.JPG
IMG_5922.JPG (195.1 KiB) Viewed 4885 times
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Re: Sidequest: VGA scan doubler

Post by exxos »

If I feed the VGA board blanking direct to the DAC it does this...

IMG_5923.JPG
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IMG_5924.JPG
IMG_5924.JPG (463.27 KiB) Viewed 4877 times
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Sidequest: VGA scan doubler

Post by exxos »

Oh this is odd...

Like there is a missing pullup or something...





EDIT:
Even more odd, I just split the cables a tiny bit and the problem has gone away.. I think it needs a pull up on Hsync somewhere..

EDIT2:

Its hard to work out, but I think they all need a pullup other than Vsync maybe..
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Re: Sidequest: VGA scan doubler

Post by exxos »

BOGDE WIRES :excited: :excited: :excited:

IMG_5930.JPG
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IMG_5931.JPG
IMG_5931.JPG (276.02 KiB) Viewed 4859 times
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Smonson
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Re: Sidequest: VGA scan doubler

Post by Smonson »

Awesome! I wonder why it needed that? The logic signals are buffered so they're supposed to be driven with a decent amount of current. Still, I'm glad you were able to sort it. Looks good now!
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Re: Sidequest: VGA scan doubler

Post by exxos »

Smonson wrote: Thu Dec 31, 2020 10:54 pm Awesome! I wonder why it needed that? The logic signals are buffered so they're supposed to be driven with a decent amount of current. Still, I'm glad you were able to sort it. Looks good now!
I suspect the GLUE doesn't drive them high, so buffering wouldn't help.

I might try closure tomorrow ;)

Great board anyway! Just sorry its taken so long to get some time to actually test the thing!
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Sidequest: VGA scan doubler

Post by Smonson »

I may need to revisit how they're buffered I guess! Thanks exxos!
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Re: Sidequest: VGA scan doubler

Post by Smonson »

Hello again,

My soldering oven worked! I made up the first prototype from design v0.4 today. This one incorporates the cut-out hole for the capacitor, plus pull-ups on IO lines recommended by @exxos. Soldering with an oven and a proper stainless-steel stencil went much faster than doing it with a syringe and a hot air reflow tool. And with the added bonus that the ICs can "float" into the perfect position with surface tension!

Anyway the cut-out hole for the electrolytic capacitor that's right in the way worked fine. The only problem is that I was so focused on getting that one right that I didn't notice that a second capacitor at the top edge of the board is actually close enough to touch too. It's a tight fit, but it goes in with minor bending! And before you ask, yes, that is what she said.

vidout15.jpg
vidout15.jpg (407.1 KiB) Viewed 4291 times

I was thinking I would like to use proper 40-pin plastic sockets for the shifter for this revision as I prefer them, but unfortunately the ones I got from Mouser don't fit over the row of header pins that are just inside the bottom row. I could maybe try cutting them down with side-cutters, but for now I just stuck with the old faithful machined pin socket strips.

I have to recompile the FPGA code to suit the new pinout before I can physically test this thing. But now I've already got a plan for the next one.
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Re: Sidequest: VGA scan doubler

Post by Icky »

Nice work @Smonson. The oven makes easier work of building.

Shame on the other cap, the joys of development. Nothing ever goes seems to go right the first few times. @exxos and i seem to burn through board versions with the issues we have in forgetting things or eagle causing issues. Is this a 2 or 4 layer board? and are the components only on the topside?
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