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Old 16 October 2006, 17:04   #1
Brass
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Retrogames - NEED Vga monitors.

I have been investigating with some help from an unfortunatly very busy local source the possibility of getting Amiga video output at 15.625 Khz upto 31+Khz on a PC Monitor - not a Multiple fixed frequency monitor but an actual Mutlisync Digital contolled IBM PC monitor, not just for Special modes but for all modes.

We think it is possibly using a couple of IC's but do need some help from people in the Amiga community that have more than a modicum of Electronics knowledge.

The guy I have been getting help from as I said is way to busy now ... but this can be done and in its simplist form could be done with about 3 common ICS and a few odds and bods.

I dont have enough nouse to complete it however - can anyone help?
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Old 16 October 2006, 17:14   #2
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It's called a _SCANDOUBLER_ they were invented years and years ago and you can buy them from all good Amiga stockists

As for being able to do it with 3 IC's, I wonder which ones they are or how much they cost? Probably cost more than a traditional Amiga scandoubler.

Remember you are going to have to buffer an entire field of data if you want to flicker fix as well as scandouble which is a fair few kbytes for the highest resolution AGA interlaced screen.

Most scandoublers dont work with the majority of LCD monitors. The vertical refresh of the scandoubled screen will be 50Hz (60Hz in NTSC) and the minimum vertical refresh supported of most LCD panels is 56Hz!

Last edited by alexh; 16 October 2006 at 17:22.
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Old 16 October 2006, 23:09   #3
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I dont know if youve quite cottoned on to what I mean

All I am attempting to acheive is Horizontal scan double and wave form double at present _NOT_ flixer fixing or de-interlacing this is simply to get the horizontal scan rate up to VGA monitor spec. Im not quite that insane. this is simply to get the old gaming resolutions up and running and available at boot time without any software requirement and _CHEAPLY_ im all about cheap

When I placed my veiwsonic onto my Amiga using the commodore adapter 390682-01 the horizontal scan rate was still 15.625 Khz.

Now the chips that I am looking at using are _COMMON_ enough and will probably cost less than 20NZ$

The idea is to only scan and frequency double where the horizontal rate is below 31.5 KHz this it seams can be acheived with relitive ease.

As for de-interlacing - this is a future project but I would look at doing it on the fly probably with a pixaxe.

Again - if there is anyone out there with electronic knowledge please let me know.

As for those little boxes I got a unit from Mayflash and can tell you it dont work and thier support is non existant

Cheers for the reply tho.
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Old 16 October 2006, 23:23   #4
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To scan double you have to buffer an entire line (maybe closer to 2)

You write to the line buffer once at 15KHz and you read it out twice at 31KHz. The time taken to fill the buffer is the same time it takes to empty it.

It would take 2 minutes to do in VHDL with even the smallest FPGA.

However you need to remember that at the 23-pin connector the signals are ANALOG they are not TTL.

If you intend to make something that connects to the Amiga video connector you will have to digitise it (A2D) and after scandoubling you will have to convert to Analog (D2A) which you could do with a simple R2R ladder.

If you have some idea about what chips you are going to use... post the datasheets here.

What is 20 NZD in real money? Hmm.. about 8 quid... that means that your scandoubler is going to cost (to make) at least 25 (70NZD).

Last edited by alexh; 16 October 2006 at 23:30.
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Old 17 October 2006, 03:55   #5
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What was indicated to me as a good place to start

http://www.maxim-ic.com/appnotes.cfm/an_pk/3327

This is the IC that was indicated to me as being a good place to start, in addition to this I have been doing a lot of research about phase descrimination circuits in order to confirm that the frequency is within range for doubling before it is doubled.

Descrimination can be acheived with a 74LS123 and a 74LS74.

I am researching another IC ATM which is a standard LM componant which provides much the same capabilities as the Maxim as well as another IC which acheives the same result but in a somewhat easier fashion I.E no other componants.

Your input would be welcomed
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Old 17 October 2006, 10:26   #6
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What really happens in a scandoubler:
http://eab.abime.net/showthread.php?t=25865

Check out..
http://www.aminet.net/package.php?pa...yncdoubler.lha

See if you can accelerate all signals and then leave black lines in between so you can achieve a fullscreen pic without buffering?

Synchronization of the accelerated sync + rgb signals may be a problem? Or perhaps a load of trimmers for the user to tweak.. :-)

It turns out that he made a second version of the project:
http://www.aminet.net/package.php?pa.../hack/sdii.lzh
Still no line acceleration, but digital controls to scroll the wide image horizontally. :-)

I'm not sure if that chip of yours will be able to accelerate the actual rgb signals.. the sync is easy enough since it's just 1010101010 at a set pace.. However the colour signals do not pulse at a set pace. :-(

Last edited by Jope; 17 October 2006 at 11:10.
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Old 17 October 2006, 15:12   #7
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RGB Clock timings

Im Sorry but the person who I have been dealing with informed me that there were no clock timings within the colour signals just within the syncs. Is this not the case?
Bare in mind this guy fixes Amigas.

The maxim chip mentioned for a fixed frequency ergo 15.625Khz does not just double the timing but the width of the pulses as well, where t=1 from rising to trailing edge t now is 2 see the example in the previous link to maxim , it shows oscilliscope timings.

Which should mean that all the colour data now fits within the new HSync.

It just has to get on screen, I can worry about other things like interlace and flicker fixing later, ill say it again all I am trying to do is get VGA output for the amiga gaming modes at present ... NOTHING MORE ...
i.e whatever the HSYNC is like 15.625 I would like it to be 31.5 this in theory should get the picture onto a VGA screen if there are no timing signals withing the RGB.

If you beleive that there are timing signals withing this data can you please provide a URL which indicates this.
BTW if there is timing data within the colour signals there surely would be nothing wrong with setting the colour frequencies in the same way as the pulses would be expanded to meet the horizontal frame time. The only difference would be you would use four PLLs not 1 , the initial one to determine the doubled frequency and then the rest to expand the colour data. I.E it wouldnt mater because you were using one base frequency to spread the data over timing signals within the RGB would be fairly erelevent.

Scuse speeling.

Cheers In advance

Last edited by Brass; 17 October 2006 at 15:24.
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Old 17 October 2006, 22:08   #8
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Hi, there are no timing signals in the colour signals, that's what the sync pulse is for. The monitor is synchronised to the computer and the computer just spits out the values through the rgb pins at the right time.. The monitor's cannons then draw the equivalent of these pulses in the correct place according to the hsync / vsync.

However, like the two above lha packages' contents tell you, a 15kHz line takes double the amount of time to draw than a 31kHz line. What do you think happens on the screen when you're syncing the monitor to draw two lines in the time that machine uses for sending one?

You need some way to make the colour signal go faster, and I think the only way to do that is to buffer it and then immediately read it twice..
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Old 17 October 2006, 22:59   #9
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Signal speed

Ok I think ive got this sussed now, looking at the scan doubler on aminet that you mentioned i think I know what it does, it doubles the sync yes but it times the writing of the colour data to the new sync pulse - thats where the timing comes from - now I understand what you are saying.

Looking at this circuit also - if you removed the output stages and converted the output to a digital signal using a 3 channel ADC you could then store the data to RAM on change of the timing pulse resulting in a frame (line) being in the devices ram.

I wonder how well flicker fixing would go if you read line 1 then line 2 while writing line 1 and so on, this would result in only a small a ram being required. duel ported ram could be used so that it could be written to on odd cycles and read from on even ones.

Just a thought
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Old 18 October 2006, 02:18   #10
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sounds to me like a project is brewing.... *interesting*


now just a touch of salt... a smidge of nutmeg....
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Old 19 October 2006, 14:21   #11
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Getting components together.

Im getting components together ATM I dont like the prototype board much tho the copper circlets keep lifting I think to make my own life easier I might get a silver conductive track pen tomorrow so I can draw the tracks.. it should make the task a tidge easier.

Some of the componats are like hens teeth too and I have had to make some mild substitutions like using the B part version of the transistor.

Not much of a choice Im afraid as many of the electronic stores here are getting into selling equipment and not electronic parts.

I had trouble today for example getting 3 25v 680uF low esr caps just to repair my router ( bloody japanese faulty electrolytic compond ) its taken out a mobo and the router so far, luckily replacing them fixes the problem.

But as an example I got the last three of that type I had to go to 3 shops in 3 different parts of the city to get them and none of them are planning to sell components anymore, anyone know a good cheap online source
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Old 19 October 2006, 14:42   #12
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Designing a scandoubler is VERY VERY easy. Actually being arsed to make one that is another thing altogether.

Quote:
converted the output to a digital signal using a 3 channel ADC you could then store the data to RAM on change of the timing pulse resulting in a frame (line) being in the devices ram.
Yup. You need a DAC on the other side of the RAM to convert back to Analog for the monitor. You can use R2R ladders instead of a DAC but make sure you get your values right.

Quote:
I wonder how well flicker fixing would go if you read line 1 then line 2 while writing line 1 and so on, this would result in only a small a ram being required.
The TV sends lines interlaced. That is all the odd lines followed by all the even ones i.e. 1, 3, 5, ... 575, 2, 4, 6.... 576. You have to buffer lines 1-575 (288 lines) if you want to then output them as progressive (flicker fixed) 1,2,3,4 etc.

Quote:
duel ported ram could be used so that it could be written to on odd cycles and read from on even ones.
You dont need a dual-port RAM if you are going to read and write on alternate clock cycles. Because you are accessing sequential locations you just make the RAM 2x as wide and read/write two pixels at once on alternate clock cyles.

Quote:
I might get a silver conductive track pen tomorrow so I can draw the tracks.
Watch your impedance on the analog signals.

Last edited by alexh; 19 October 2006 at 14:47.
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Old 19 October 2006, 14:43   #13
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I know a couple of stores on ebay that might help.

http://stores.ebay.co.uk/Bitsbox-Electronic-Components

http://stores.ebay.co.uk/TECHNIXPLUS

I find these places have a good range of components, more exotic ones might have google or replace them with their russian equivilants LOL
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Old 20 October 2006, 15:57   #14
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Have pen will etch

Well ive spent a fair whack of time (5 hours) etching away at prototype board and filling in gaps with circuit writing pen.

In the morning ill be able to bake it and cure the tracks then its plonk the componants on time. and try and get the thing up and running. Managed to get some BC547s with no letter at the end too they got them in today in fact they gave me a dozen when i wanted six because they had to many.
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Old 20 October 2006, 20:59   #15
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I look forward to seeing the results Brass, I have been using a lot of copper tape and pens of late.. I got a lot of prototype boards (without copper) for extrememly cheap as in the el-cheapo of cheap. still the hold components works for me...

It would be nce to see picies Brass... i like picies...

picies and linkies... my life evolves around them

please postie picies
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Old 21 October 2006, 12:12   #16
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Trust me these aint pretty

I used a silver conductive pen the results aint pretty and Im getting someone who is more expert in electronics look over them before I proceed as I had to alter the circuit slightly due to running out of room on the proto board.
Hopefully its all correct and ill be able to fire it up soon, If its not right at least ill be able to go back to him and have him test the thing and find the problem.

Hes excellent at that stuff ive only got basic knowledge and I discovered today age must be catching up with me... the level of shakes just trying to wield a soldering iron was just rediculous.
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Old 22 October 2006, 16:09   #17
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Its looking good Brass!!!!!!
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Old 22 October 2006, 19:59   #18
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if you could make them in series and sell them, you could make lots of cash!! (provided they work )
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Old 23 October 2006, 03:51   #19
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after prototyping comes Circuit Board printing, then acid eching and then neutralising and then mounting the components

at this point kits could be sold i'd buy one! build it into a project box and voilia (just thinking of that Jammer Cabinet now.... mmmm )

I am hoping brass could then develop this a possible mass produced product that would be cool... theres an SMeC based company about a couple miles away they might take on small product runs... when i discussed a product run with them for my usb based eprom programmer/reader (4 years ago now) there minum run (after prototyping) was 200 units.

cost depends on the number of layers the board needs etc. but whom knows iy might be cheaper in NZ

Once Brass has his prototype up and running, All it takes is a little touch here and there for a composite input and maybe (dependant on cost) an RF input.. would be nice to see Atari VCS/2600 on a big crt

infact theres lots of things one could use it for, VCR's, DVD players / Records, old school consoles its all good ) .

Last edited by Zetr0; 23 October 2006 at 03:56.
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Old 31 October 2006, 07:00   #20
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Wiring

Hi guys Im now at the final wiring point, I have created gerber files for the unit so its ready to be milled if required.

I have a minor problem at the moment though, has anyone on EAB got the ability to read German and translate it ledgibly to english as there are a couple of things that are not making sense at all.

BTW : Do you like my circuit board stands, they are the lid supports from two Pizza boxes.
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