MiSTer FPGA Forum

Hello,
I was asking myself if using Mister as a scaler for external source would be possible ?
When i bought the de10 nano i red in the datasheet that there is an adc onboard, with a connector of it's own. I look again and it's a LTC2308, a 12 bit 8 channel adc (but my electronics knowledge is too limited to know if this adc could handle a video signal).
As i was recently into thinking how to downscale a few games to 240p for crt, it's how i thought of this.

There is in fact scaler available to do this, but most of them do not do downscale. There is a page that talk of this (http://scanlines.hazard-city.de/), but most of these scaler are old and could be more expensive now or hard to find... i check quickly on ebay and it's a lot more expensive compare to when the hazard-city page was written, also enjoy the shipping cost if you don't live in the US.

I don't look much into the other solution like ossc or framemaster, but i remember that they are expensive especially for what i would do with them, so if it's doable i'm sure a mister solution could save a lot of money for a few mister users...

Also i read on the forum that users here did downscale some 480p content from old computer's core to 240p for there crt that only support 15khz.

This solution could be excellent for crt users to downscale some content (modern-retro games from pc or console) or to convert interlace to progressive. Or of course to upscale some console that don't exist as Mister core yet (for example i don't expect to see a PS2 core before long ).

Have a look into GBS Control
for a cheap available up / down scaler

GBS Control looks interesting, it seems like a DIY device though, not sold anywhere.

OSSC/Framemeister can downscale to 240p? I always thought they are upscalers. Think I read on shmups forum you need a Corio-style downscaler to do eg PC to 240p (and these are expensive too).

I also don't think it's quite possible to downscale 480p in MiSTer, where did you see this @Atohmdiy? I would be most interested to try that.

akeley wrote: ↑Thu Aug 13, 2020 11:38 am GBS Control looks interesting, it seems like a DIY device though, not sold anywhere.

It's based on a widely available and cheap scaler and just requires a fairly simple modification to turn it into a really good scaler which is still being improved. You won't get better value than that, ESPECIALLY if you want to downscale as this is a feature reserved for very, very expensive devices.

That may be so, but my electronic building skills = 0, so unless it's possible to buy a ready made unit somewhere it is not an option for me. Also most results for my GBS Control search queries talk about the up-scaler versions.

I actually use crtemudiver to display PC on my CRT TVs, but it's a cumbersome method, with many caveats. So, a little not-too-expensive box doing this job the hardware way would be an insta buy for me.

https://medium.com/rgb-inside/gbs-8200- ... 5d3b6907be

If you really can't build one here's a preassembled unit, still cheaper than an OSSC (which can't downscale until the Pro comes out):

https://gamescare.com.br/produto/gbs-co ... ler-1080p/

Thanks for the links. It is indeed a very interesting device. I will investigate, maybe somebody sells them in Europe too.

There is this short discussion about using the scaler to downscale to 240p :

viewtopic.php?f=33&t=780

I made some research today about this GBS Control, and it seems incredible indeed, and it's very cheap. The board + wifi module + external clock is 24€ include shipping. Only a case seems a little tricky to find, some offer 3d printed case but it's 30-45€ + shipping, a lot more than the price of the scaler. Hopefully a friend told me he knows someone with a 3d printer

But still if it doable in mister it would be great. Mister already have the scaler plus an adc onboard, in a way it is just replacing the video data from the core for the one that come from the adc. I am not sure anyone want to ear this as it's not a goal of mister, but it should really be a wonderful addition. This gbs control is nice, but we shouldn't forget it stay chinese crap with some modification to make it work correctly, and during my reading some says these board are very unreliable... at this price we obviously cannot ask for the moon. Also to have this option in mister make it (even more...) an all in one solution, and it's after all the big strength of mister compare to software emulation.

According to the DE10-Nano manual, the ADC has a 500Ksps sampling rate. I don't think that's anywhere close to enough.

For instance, if I'm following the superfamicom.org timing wiki page correctly, between "The SNES master clock runs at about 21.477MHz NTSC" and "The PPU outputs one pixel every 4 master cycles" that means it outputs pixels at about 5.4MHz. Maybe double that for Nyquist purposes and I think you'd want at least 11Msps just to read individual pixels from a rather low-resolution source.

As a comparison, the XRGB-3 scaler used a AD9883AKSTZ-110 as its ADC which can do 140Msps.

One of the options for the OSSC Pro will apparently be an add-on board for the DE10-Nano. Apparently it will use an ISL51002 as its ADC which can do 165Msps. Looks like it would plug into the same GPIO connector as MiSTer's SDRAM, which is unfortunate as it would make switching between MiSTer and OSSC Pro a pain. Though I don't know if any of this information is out of date.

I don't think you qre supposed to switch between MiSTer and OSSC, they just both use the DE10 Nano as a building piece. If the schematics are open though, maybe somebody will end up merging the pcbs into an "upscaler IO board" of sorts.