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Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 05:29
by Smonson
You can see some muddiness in the black when there's a black background - that's probably just a result of me not having added the wire for BLANK to my ST yet.
dont-you-worry-about-blank-let-me-worry-about-blank.jpg
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 07:04
by nikoskon
Just out of curiosity, and please excuse my ignorance, i have an STE, but have no idea where this would sit?
Will it work in an STE?
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 08:54
by Smonson
nikoskon wrote: 29 Jul 2020 07:04
Just out of curiosity, and please excuse my ignorance, i have an STE, but have no idea where this would sit?
Will it work in an STE?
Unfortunately, there are a couple of snags getting in the way of that:
- There's no easy way to plug something like this into a socket, each wire would have to be individually soldered to the main board
- I don't have an STE to try it on
I guess as long as the 32MHz clock is available, it'd be possible to do this in theory on an STE... The 12 RGB lines out of the GST shifter would, I assume, go to a resistor ladder, so you could attach the RGB lines there by lifting the resistors. I'm using 16-bit RAMs so there's enough data lines to fit the extra bit for each colour - although we'd need to add 12 additional IOs on the FPGA to include them (3 each for RGB in, RGB out, and the 2 RAM buses).
That's a mountain that's waiting for its own Hillary.
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 09:10
by nikoskon
Smonson wrote: 29 Jul 2020 08:54
nikoskon wrote: 29 Jul 2020 07:04
Just out of curiosity, and please excuse my ignorance, i have an STE, but have no idea where this would sit?
Will it work in an STE?
Unfortunately, there are a couple of snags getting in the way of that:
- There's no easy way to plug something like this into a socket, each wire would have to be individually soldered to the main board
- I don't have an STE to try it on
I guess as long as the 32MHz clock is available, it'd be possible to do this in theory on an STE... The 12 RGB lines out of the GST shifter would, I assume, go to a resistor ladder, so you could attach the RGB lines there by lifting the resistors. I'm using 16-bit RAMs so there's enough data lines to fit the extra bit for each colour - although we'd need to add 12 additional IOs on the FPGA to include them (3 each for RGB in, RGB out, and the 2 RAM buses).
That's a mountain that's waiting for its own Hillary.
Didn't look like it would fit/work in an STE and sounds like a whole heap of work too :shock:
But great job on what you have accomplished with this board either way :D
Seems like i'll have to get my hands on an older STFM if i want something like this though :)
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 09:39
by Smonson
You can also use an external scandoubler like the OSSC on an STE (if you can get your hands on one), which gives amazing results according to what I've heard. It works basically the same way except that it's not timed to the Atari's internal clock, and it has to pass the signal through an extra analogue step before output.
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 11:07
by stephen_usher
I concur, the OSSC output is extremely good, especially if you enable the 2x oversampling of the signal. However, you do get some "jail bar" noise potentially.
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 11:28
by beel1
I didn't measured precisely but on my STE the resistor ladder and the mono output resistor look like they are neatly arranged in a 4x13 0.1" matrix under the power supply. Maybe they can be replaced by a header and put on a daughter board along with the scandoubler circuitry :idea:
But anyway I too have opted for external scandoublers (GBS8200 and a Pioneer media receiver)
Re: Sidequest: VGA scan doubler
Posted: 29 Jul 2020 14:29
by Smonson
beel1 wrote: 29 Jul 2020 11:28
I didn't measured precisely but on my STE the resistor ladder and the mono output resistor look like they are neatly arranged in a 4x13 0.1" matrix under the power supply. Maybe they can be replaced by a header and put on a daughter board along with the scandoubler circuitry :idea:
But anyway I too have opted for external scandoublers (GBS8200 and a Pioneer media receiver)
Yes, that would be a great way to do it. Although it's still a decent amount of soldering to pull out that many resistors.
You'd need the 32MHz clock line, the 12 RGB lines (in as well as out), the mono pin (in only), hsync (in and out), vsync (in) and blank (out only). I think that's everything. 30 in total. And 5v and ground of course.
Re: Sidequest: VGA scan doubler
Posted: 30 Jul 2020 03:55
by nikoskon
Smonson wrote: 29 Jul 2020 09:39
You can also use an external scandoubler like the OSSC on an STE (if you can get your hands on one), which gives amazing results according to what I've heard. It works basically the same way except that it's not timed to the Atari's internal clock, and it has to pass the signal through an extra analogue step before output.
Thats what i have currently, OSSC outputting to monitor. It does work really well in medium resolution, but haven't been able to get high resolution out of it yet. Don't get the option to enable it when in GEM.
Is there a way to get the high resolution mode out of the Atari with the OSSC? although i've noticed (reading through some threads in various forums), that colour is not an option in high res :(
Re: Sidequest: VGA scan doubler
Posted: 30 Jul 2020 08:58
by stephen_usher
You’ll need an adapter to do high res as it needs to pull a line up on the connector at the very least. There are ST-to-VGA adapters which will do this.