Sporniket's log on hardware stuff

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sporniket
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Re: Sporniket's log on hardware stuff

Post by sporniket »

Thank you. What puzzles me is the mechanism that would converts the HSYNC source pulses into serrated CSYNC pulses when VSYNC is low.
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exxos
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Re: Sporniket's log on hardware stuff

Post by exxos »

sporniket wrote: Sun Nov 15, 2020 4:11 pm Thank you. What puzzles me is the mechanism that would converts the HSYNC source pulses into serrated CSYNC pulses when VSYNC is low.
Its just a simple logic.. If vsync or hysnc is low then csync is low. Its still a composite signal format, just its missing RGB information.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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sporniket
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Re: Sporniket's log on hardware stuff

Post by sporniket »

exxos wrote: Sun Nov 15, 2020 4:15 pm
sporniket wrote: Sun Nov 15, 2020 4:11 pm Thank you. What puzzles me is the mechanism that would converts the HSYNC source pulses into serrated CSYNC pulses when VSYNC is low.
Its just a simple logic.. If vsync or hysnc is low then csync is low. Its still a composite signal format, just its missing RGB information.
Thank you.
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Re: Sporniket's log on hardware stuff

Post by DoG »

Looked at this old thread at Atari-Forum? The link goes directly to the circuit they use to combine HS and VS. They use 2 XOR gates in a 74LS86 to solve the problem.

But creating schematics and doing small PCB is nevertheless a fun project.
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Re: Sporniket's log on hardware stuff

Post by exxos »

Still really needs a driver transistor as logic might not output enough current if its 75R terminated .

Even so a simple 2 input AND gate would do the same job. If either input is low then the output is low.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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sporniket
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Re: Sporniket's log on hardware stuff

Post by sporniket »

DoG wrote: Sun Nov 15, 2020 6:30 pm Looked at this old thread at Atari-Forum? The link goes directly to the circuit they use to combine HS and VS. They use 2 XOR gates in a 74LS86 to solve the problem.
Yes I also found this schematics when doing research. I will also do a version using that.
DoG wrote: Sun Nov 15, 2020 6:30 pm But creating schematics and doing small PCB is nevertheless a fun project.
yes.
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Re: Sporniket's log on hardware stuff

Post by sporniket »

exxos wrote: Sun Nov 15, 2020 6:34 pm Still really needs a driver transistor as logic might not output enough current if its 75R terminated .

Even so a simple 2 input AND gate would do the same job. If either input is low then the output is low.
Thanks for the advices.
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Re: Sporniket's log on hardware stuff

Post by sporniket »

Today I got the donor machine for the H5 build, now eagerly waiting the remaining parts (I believe that my H5 seems to be in the customs office for now since the 27, because it is still at Roissy CDG airport...).

Anyway I did a little check-up... one disassemble/reassemble cycle...
2020-12-05--donnor-machine-01.jpg
2020-12-05--donnor-machine-01.jpg (133.05 KiB) Viewed 6698 times
2020-12-05--donnor-machine-02.jpg
2020-12-05--donnor-machine-02.jpg (171.88 KiB) Viewed 6698 times
And then the faithful diagnostic cartridge
2020-12-05--donnor-machine-03.jpg
2020-12-05--donnor-machine-03.jpg (55.78 KiB) Viewed 6698 times
Checked the RAM, the Color and the OS, only the latter seems to have problem. I don't mind given that the ROM will not be of use.
2020-12-05--donnor-machine-06.jpg
2020-12-05--donnor-machine-06.jpg (47.36 KiB) Viewed 6698 times
I noticed that the video is quite noisy. It's a little bit noticiable at 60Hz (the slight embossing effect on the right)
2020-12-05--donnor-machine-04.jpg
2020-12-05--donnor-machine-04.jpg (26.66 KiB) Viewed 6698 times
And more noticiable (and moving) at 50Hz
2020-12-05--donnor-machine-05.jpg
2020-12-05--donnor-machine-05.jpg (19.88 KiB) Viewed 6698 times
So, the PSU of this machine will no get near my H5 build...
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Re: Sporniket's log on hardware stuff

Post by sporniket »

On the schematic front, and my script to generate Kicad symbols from structured Markdown datasheets of an arbitrary IC.

I was pondering about generating big custom ICs as multi-unit symbols in kicad in order to create schematics focused on a group of signals (say, the distribution of the clock signals), and took the time to implement that.

Then I created the source datasheet for the GSTMCU of the STE (the page of info-coach was extremelly helpfull for that). And it is so huge that I would need to setup an A3 sized page to accomodate the symbol. So I feel right about splitting big ICs. Next step will be to create a POC of schematics with a few more ICs to assess the readability and the understandability of the resulting document.

for the curious, here are a sample sheets demonstrating the blitter and the gstmcu as single unit vs multi unit.
a-ste.pdf
(188.61 KiB) Downloaded 198 times
And this is the generated libraries that are used in this demo :
wip-symbols-custom-ics.zip
(5.02 KiB) Downloaded 201 times
By the way, while drawing the schematics, the subtext describing the unit is not visible, I don't know how to show it. Fortunately, it is visible on the printed/plotted schema.

I must have mentionned it before, but the source project is here : https://github.com/sporniket/retro-comp ... schematics
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Re: Sporniket's log on hardware stuff

Post by sporniket »

Got my H5 B1 this morning, still waiting my last order of IC sockets that exxos shipped recently, then I will be able to start my build.
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