CoZe's Scandoubler Project - Help needed !

[tnt23]

You've probably seen the scandoubler project page at Elm Chan:
http://elm-chan.org/works/sc/report.html

also mentioned in this thread:
http://eab.abime.net/showthread.php?t=25865

The schematics look terribly similar to those of Amber found in A3000's manual.

[coze]

Thanks everybody for the great advices

Originally Posted by Stedy

A few hints. For the 5 to 3.3V conversions, look for a 74LV245, or similar logic device. This is an 8 bit wide data buffer that operates off 3.3V but is 5V tolerant.

Thanks ! I'll have a look into that

Originally Posted by Stedy

The DAC0832 D/A converter is not suitable. It has a settling time of 1us or throughput of 1MHz. Typically when working with Video signals, you use 27 or 54MHz parts (2x and 4x pixel clock). Look at the Analog Devices ADV7120 for an idea or two. As most fast D/A converters are current mode, you typically add a 37.5 ohm load to convert current to volts and allow you to drive 75 ohm cables.

Ah a triple 8 bit DAC ! This looks really good, thanks !

Originally Posted by Stedy

Likewise, to sample the RGB video, you need a fast ADC or use a video decoder. The Analog Devices ADV7401 accepts RGB, Y/C or CVBS video and outputs the sampled video data as RGB 4:4:4 data.

Like Alexh said, I'm planning to interface this directly to Amiga digital RGB signals, so an ADC covnersion will not be necessary.

Originally Posted by Oli_HD

Dont even think about using a CPLD as a FIFO, with its NAND gate design it would need about 5000 microcells or something silly like that.
Try compiling the Minimigs scandoubler code, you couldnt use it but Dennis built the line buffer into the FPGA so would show you just how big a CPLD you would need.

I think line buffer will be ok (to keep a single or two scanlines). But yeah, probably I won't be able to fit a whole frame there. I'll do what you said and see if it fits. For a comparison, this CPLD has 2200 logic cells, while the DE1 board has 20.000, but it can house the full minimig AND a softcore 68000 (and %30 space remaining, TobiFlex said somewhere).

Originally Posted by Oli_HD

What is a much (much much) better option is to just buy a AL251 scan doubler chip and wire it up to the digital signals and you are done.
For OCS/ECS thats fine, its 16bit. Use FIFO memory would let you do 24bit though.

Yes, for ECS it would be much painless but I would like to eventually make this an AGA scandoubler so I don't want to take that route. I'm not sure I get what you mean by using FIFO memory for 24 bit.

Originally Posted by tnt23

You've probably seen the scandoubler project page at Elm Chan:
http://elm-chan.org/works/sc/report.html

Yes, I checked that one before, but it looked too dependant on NTSC video clocks and it has very little future expandability for interlaced modes. I think it would be a real hassle to modify that design recognise and support amiga modes, I thought it's better to start from scratch with available modern hardware (most parts used in that project seems unavailable). But it gave me some good ideas, so thanks !

[mc68k]

What is the current status of this project?

[alexh]

Dead for at least 7 years?

[mc68k]

A quick poll:

Are You guys interested for an ECS scandoubler, with analog VGA output?

http://amigaprj.blogspot.com/2015/04...500-a2000.html

The final price will be ~60-70 EUR.

[alexh]

I applaud your project however I think the market is all but gone. Especially at that price.

Those who had money and we're super interested bought the Indivision ECS (€90) years ago. It's extra chunkey screen modes offered some interest developers and novacode supported it in several releases of game ports.

Those who were interested but on a lower budget bought either a cheap RGB SCART to VGA (or HDMI) off Amazon (€30) or the GBS 8200

With the Vampire A500 almost here with built in SAGA there is even less of a market.

[jarp]

While I appreciate all DIY projects hugely, I must say, that... VGA only? No DP or HDMI? Very sorry, but I've not had any equipment at home which would accept VGA in years. While some Amiga enthusiastic probably are prepared to buy some equipment just for Amiga, they are buying 15kHz compatible monitors as well so any VGA-only scandoubler offer very little.

This is of course only my opinion and I actually hope I am wrong All homebrew stuff is always great.

[happymondays]

Well, if you want to use your machine with a CRT monitor (manufactured from the end of 90s up until the end of the CRT era) not specifically built for Amiga, then most probably it will have a VGA connector. I use my scandoubler on a CRT with VGA for a bit more than 18 years now. It looks way better than on any LCD and I don't think I am alone with my opinion.