Hello, me again!
So, I like to have several projects going at once, as you have probably guessed from my short attention span.
I wanted to get started with small and very cheap FPGAs (as opposed to the huge and expensive Cyclones) so I picked up some MAX-Vs in my last Mouser order. These guys go all the way down to $1.32 each.
So I decided to do a VGA scandoubler that reads the RGB values straight out of the shifter into a couple of SRAMs. I started several months ago and today came to a point where it's worth discussing. Here's what it looks like plugged in:
The MAX-V is at the bottom centre. The two SRAMs on the right alternate between reading and writing. The addresses on both are generated by ripple counters (above the SRAMs). At the top are the three DACs for RGB, and the VGA pin header. I had to do a couple of fix-up wires, which is fun on an EQFP-64 with 0.4mm pin spacing.
Unfortunately the picture isn't great right out of the gate. It looks like it could be because of address lines changing in the middle of reads or writes, and thus reading or writing to/from the wrong address, but I haven't been able to narrow it down any further than that so far. Because I took the photo on my phone, it's got that annoying moire pattern on the pic, but you can see the vertical green lines on the right half for example. The dodgy pixels are also quite evident in the menu bar due to the presence of lots of text.
Anyway, apart from the "reflections", the image is quite stable and crisp, and the colours look right. So that's something I guess!
I'm probably violating the timing requirements for VGA, but you can't have everything.
Sidequest: VGA scan doubler
Re: Sidequest: VGA scan doubler
A cheapish scan doubler will do wonders for the ST community - awesome!. Everyone with a socketed Shifter can plug'n'play it right out the gate I assume?
/Troed
/Troed
Re: Sidequest: VGA scan doubler
Yep, assuming that they have access to a monitor that can display a 50hz image via the VGA input. I'm assuming that many TVs would fall into that category but I've only tried one so far. Monitors are less likely to work.
Re: Sidequest: VGA scan doubler
...actually one thing I forgot to mention. It does require a connection to HSYNC, which means soldering to a via near the GLUE. So it's not totally plug-and-play unfortunately.
Without HSYNC, it can't tell where to begin the scanlines.
Without HSYNC, it can't tell where to begin the scanlines.
Re: Sidequest: VGA scan doubler
Another interesting project, well done.
If it ain't broke, test it to Destruction.
Re: Sidequest: VGA scan doubler
As I don’t know shit about Atari this might be a stupid question, but would this be possible to adapt to the Amiga? What are the input signals?
A cheap-ish scandoubler that attaches to the DB23 RGB Port of the Amiga would be a welcome addition to the community.
Sorry I’m advance if this is way off topic.
A cheap-ish scandoubler that attaches to the DB23 RGB Port of the Amiga would be a welcome addition to the community.
Sorry I’m advance if this is way off topic.
A kludge is a workaround or quick-and-dirty solution that is clumsy, inelegant, inefficient, difficult to extend and hard to maintain.
My lack of focus:
[ 4 * Amiga 500 ][ Amiga 500+ ][ 2 * Amiga 600 ][ A1200 ][ Amiga 2000 w/ A2386 ][ Amiga 4000/030 w/ CyberVision 64 3D, FastLane SCSI Z3 ][ CD32 ][ VIC-20 ][ 4 * C64 Breadbin ][ 5 * C64C ][ 2 * C128 ][ C128D ][ C64 DTV ][ Mac Classic ][ Mac Classic II ][ Mac Colour Classic ]
My lack of focus:
[ 4 * Amiga 500 ][ Amiga 500+ ][ 2 * Amiga 600 ][ A1200 ][ Amiga 2000 w/ A2386 ][ Amiga 4000/030 w/ CyberVision 64 3D, FastLane SCSI Z3 ][ CD32 ][ VIC-20 ][ 4 * C64 Breadbin ][ 5 * C64C ][ 2 * C128 ][ C128D ][ C64 DTV ][ Mac Classic ][ Mac Classic II ][ Mac Colour Classic ]
Re: Sidequest: VGA scan doubler
Super nice well done!
I assume your using the 32mhz shifter clock to sync the ripple counters to the video sampling ?
I assume your using the 32mhz shifter clock to sync the ripple counters to the video sampling ?
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.
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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Re: Sidequest: VGA scan doubler
Wow, that's pretty cool
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Re: Sidequest: VGA scan doubler
Nice one Smonson
Re: Sidequest: VGA scan doubler
Maybe. I'm using the 32MHz master clock, the digital RGB signals (3 bits each) out of the shifter, and HSYNC. VSYNC might also be needed for better TV compatability. I don't know how easy it is to get hold of those in the Amiga's hardware because I don't own one at this time.