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Author Topic: Side Projects: "mini" SLG & CGA->VGA converter  (Read 23652 times)

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CraftyMech

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Side Projects: "mini" SLG & CGA->VGA converter
« on: November 29, 2012, 05:06:01 pm »
In the process of working on my bartop project, I've started on a couple side projects that will go into my build. I figured I would start a separate project thread for these projects, and keep it updated as I make progress.

Project #1 - mini SLG (scanline generator)

The mini SLG is an inexpensive, and compact scanline generator that is compatible with any device that outputs a standard VGA signal @ 640x480 & 1024x768 resolutions.

Compatible devices include:

-- a PC video card
-- a multigame pcb with VGA output, such as a 60-in-1 board.
-- a CGA->VGA converter board, such as the GBS-8200

For best results, the VGA source should be set @ 640x480 resolution.

Below is a photo of the finished product (color choices are black, beige, and shiny metalized plastic), and some example photos of the mini SLG is action.

mini SLG in a black shell


Pac-Man (60-in-1 board) on an LCD @ 640x480


Fatal Fury 2 (Neo Geo MVS board) on a CRT @ 640x480 using a GBS-8200 CGA->VGA converter
« Last Edit: December 22, 2012, 02:24:41 pm by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #1 on: November 29, 2012, 05:09:03 pm »
Project #2 - CGA->VGA converter

I've been experimenting with the GBS-8200 CGA->VGA upscaler, and have not been that impressed with the standard CGA resolution conversion. So I've started building my own board dedicated to taking low-medium res CGA games to VGA @ 640x480. I'd rather build a board that does that one function really well, then fuss with an import board that has inconsistent quality, but converts a wider range of resolutions.

My upscaler design has three main stages: CGA in (ADC), data buffers, and VGA out (DAC). I've just about got the VGA signal generation worked out, so next step will be to look at building the ADC modules for the CGA in stage.

This project could be quite a journey, I'll post updates as I make progress.
« Last Edit: November 29, 2012, 05:11:04 pm by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

Yvan256

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #2 on: November 29, 2012, 05:59:24 pm »
Which ICs are used in each project?

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #3 on: November 30, 2012, 01:39:19 am »
The mini SLG is built around a Dual D-Type Flip Flop, which is also used in the SLG-3000, T-SLG and RetroVGA projects. However, those projects use an additional IC, a Quad Tri-State Bus Buffer. I found that the Bus Buffer was not needed with a few changes to the circuit layout. Removing the Buffer IC simplifies the circuit, but sacrifices the ability to change scanline widths as both Flip Flops are already in use.

For the CGA->VGA converter I've been working on the VGA out stage, and right now I'm using an ATMega microcontroller, and coding in assembly for accurate signal timing. For the ADC I'm looking at chips in the 5-8Mhz sampling range, and for the DAC I think I could get away with a R2R ladder).

The schematic has been removed temporarily due to a color balance issue (green tint) with certain PC video cards. Once the solution is worked out, I'll update the schematic.
« Last Edit: January 28, 2013, 01:31:00 am by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

Le Chuck

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #4 on: November 30, 2012, 08:19:25 am »
I don't understand all your fancy talk but if this is a magic dongle to add scan lines without software I want one!

Yvan256

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #5 on: November 30, 2012, 08:53:25 am »
The mini SLG is built around a Dual D-Type Flip Flop, which is also used in the SLG-3000, T-SLG and RetroVGA projects. However, those projects use an additional IC, a Quad Tri-State Bus Buffer. I found that the Bus Buffer was not needed with a few changes to the circuit layout. Removing the Buffer IC simplifies the circuit, but sacrifices the ability to change scanline widths as both Flip Flops are already in use.

The schematic is below. Pin 14 (VCC) on the Flip Flop is left floating, and I'll post up a bit more detail about why tomorrow.

So you're telling me you're doing all this with plain old logic ICs?  :dizzy:


For the CGA->VGA converter I've been working on the VGA out stage, and right now I'm using an ATMega microcontroller, and coding in assembly for accurate signal timing. For the ADC I'm looking at chips in the 5-8Mhz sampling range, and for the DAC I think I could get away with a R2R ladder (CGA is only 6bit color if I remember).

That would be funny if it were the ATmega328 because at the moment that little guy is helping me testing stepper motors for my CNC machines. Except I don't use assembly, C is plenty enough for my needs.  ;)

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #6 on: November 30, 2012, 10:15:48 am »
I don't understand all your fancy talk but if this is a magic dongle to add scan lines without software I want one!

It sure is! There have been other projects before mine that have implemented scan lines in hardware (SLG-3000 & T-SLG) and I got my inspiration from those designs. That said, I believe this design is the most compact so far, and the first to be squeezed into a "dongle" size adapter. I wanted to come up with something that was convenient for cramped spaces (like inside my bartop project) and fit into a ready made plastic shell so it wasn't just a circuit board (enclosures can be added to the other projects I mentioned, but that just adds to their bulk).
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

Le Chuck

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #7 on: November 30, 2012, 10:21:41 am »
I don't understand all your fancy talk but if this is a magic dongle to add scan lines without software I want one!

It sure is! There have been other projects before mine that have implemented scan lines in hardware (SLG-3000 & T-SLG) and I got my inspiration from those designs. That said, I believe this design is the most compact so far, and the first to be squeezed into a "dongle" size adapter. I wanted to come up with something that was convenient for cramped spaces (like inside my bartop project) and fit into a ready made plastic shell so it wasn't just a circuit board (enclosures can be added to the other projects I mentioned, but that just adds to their bulk).

Right-o so... how much with shipping to Phenix City AL?  I want to throw this bad boy in my bartop and see how it works.  If you don't want to sell post an instructable.  Oh, and when in vertical mode the scan lines would be horizontal I take it?   

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #8 on: November 30, 2012, 11:21:42 am »
Right-o so... how much with shipping to Phenix City AL?  I want to throw this bad boy in my bartop and see how it works.  If you don't want to sell post an instructable.  Oh, and when in vertical mode the scan lines would be horizontal I take it?

The scanlines would actually be vertical for a monitor in the vertical position (they are horizontal for a monitor in the normal upright position). What kind of monitor do you have in your bartop? I've got a deal for you, I only have two monitors to test on so I could use a couple beta testers. I have not put in an order yet to fabricate the pcbs (more like postage stamps as small as they are), but I can whip up another prototype (like the one pictured) and send it to you to try out. If you like how it works then hold onto it and we can just consider it a barter in exchange for your feedback. The difference between the prototype and the finished board is just that I hand wire my prototypes versus having the traces on the underside (the lines you see on the bottom of circuit boards). The performance is exactly the same, it just takes longer to do by hand so I would have boards fabricated before I started actually selling these. PM your address if that sounds cool and I'll get one built and shipped out to you. PS - What kind of hardware are you running in your bartop? 60-in-1 type board, dedicated game board, or PC hardware?
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #9 on: November 30, 2012, 11:33:52 am »
If you need another beta tester, I'm down. Plenty of different types of monitors I can test on. Have a 60-in-1, PC setups, and original arcade pcbs I can run through my CGA converter.

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #10 on: November 30, 2012, 11:43:13 am »
So you're telling me you're doing all this with plain old logic ICs?  :dizzy:

That would be funny if it were the ATmega328 because at the moment that little guy is helping me testing stepper motors for my CNC machines. Except I don't use assembly, C is plenty enough for my needs.  ;)

Actually I am using an ATMega328 @ 20mhz for my cga->vga converter! The ATmega line of chips are really nice, inexpensive and easy to use. There is a lot of "arduino" stuff out there, but those are just dev boards and some extra code libraries built around the ATmega series of chips. So there are a lot of ATmega projects out there that you can find source code for, and help you figure out how to make things work for your own projects. Funny you mention stepper motors, I've written drivers in C for unipolar stepper motors for the ATmega, and been meaning to get around to working out how to use PWM to implement micro stepping on a stepper motor for a 3d printer project I've been tinkering with.

Yep, just a basic digital logic IC. The HSync signal pulses at the start of every horizontal line on the screen, and when that happens the Flip Flop toggles between "0" and "1" (or vice versa). When the output is "0", the RGB signal is rerouted (connected to ground) and the result is a scanline on the screen. The fun thing about circuits like this one is that back in the late 70s/early 80s arcade boards were stuffed with logic gate ICs (hence the giant Centipede board) and all that arcade magic happened the "hard way" by today's standards. Today, you have a square surface mount IC that implements thousands of logic gates (FPGA), and they are programmed in a hardware description language, instead of designing a circuit that integrates all the input/outputs of the various chips.
« Last Edit: November 30, 2012, 12:00:58 pm by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #11 on: November 30, 2012, 12:10:11 pm »
If you need another beta tester, I'm down. Plenty of different types of monitors I can test on. Have a 60-in-1, PC setups, and original arcade pcbs I can run through my CGA converter.

Awesome Nephasth, PM your address to me and I'll get a prototype built and shipped out to you.

I think 2 beta testers will work for now. I should have a good idea by Monday when I will be able to start selling the finished product (probably late December).
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

emphatic

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #12 on: November 30, 2012, 02:33:05 pm »
Very excited to hear about your CGA->VGA gizmo. And thoroughly impressed. :cheers:

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #13 on: November 30, 2012, 03:08:58 pm »

 :stupid Aye, same here...will be eagerly following this thread for sure.

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #14 on: November 30, 2012, 03:36:14 pm »
Impressive!!

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #15 on: November 30, 2012, 05:03:42 pm »

 :stupid Aye, same here...will be eagerly following this thread for sure.

Hey, who're you're callin' stupid?  :angry:  :cheers:

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #16 on: December 01, 2012, 01:58:42 pm »
Thanks guys, I'll be sure to post updates as I make progress. My motivation for starting the project was the lack of options for arcade cga -> vga conversion. The GBS-8200 works ok, but I believe the board is doing full frame conversion in order to handle the various output resolutions, and that is where the visual artifacts are coming from. My plan is to do a line buffered conversion, which buffers the CGA signal two lines at a time, and upscales the data for 640x480 VGA output, resulting in a cleaner conversion with less artifacts.

I've been building the two prototypes of the mini-SLG scanline generator this weekend, looking  forward to getting some feedback from my beta testers on different setups.
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

emphatic

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #17 on: December 02, 2012, 07:10:48 am »
My plan is to do a line buffered conversion, which buffers the CGA signal two lines at a time, and upscales the data for 640x480 VGA output, resulting in a cleaner conversion with less artifacts.

The trade-off is increased lag though, right?

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #18 on: December 02, 2012, 01:44:08 pm »
The problem that has to be solved with CGA->VGA conversion is that the VGA signal is at least twice as fast as its CGA input (31k vs. 15k). So some sort of signal buffering has to take place, either two vertical lines at a time, or worst case two full frames at a time (480x2 lines).

So the lag calculations for best & worst cases would be:

Given 2 buffered lines of CGA signal, the signal lag would be at least 60 microseconds (30 microseconds per line @ 15k).

For 2 buffered frames of CGA signal, multiply 30x480x2= ~28 milliseconds.

28 milliseconds isn't terrible for full frame, but even with a CRT that amount of lag might cause problems for precise patterns in a game like Pacman. Throw a LCD into the mix and the lag starts getting a little ugly though.

UPDATE: I poked around the GBS board, and sure enough I found a 8MB SDRAM (S6432AFTA-6B-E) chip with burst read/write. With that size of video memory, I'm feeling confident now that the GBS uses some flavor of full frame conversion, and therefor a display lag of between 14-28 milliseconds for CGA->VGA.
« Last Edit: December 02, 2012, 02:43:34 pm by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #19 on: December 06, 2012, 09:31:00 am »
The new prototype version of the mini-SLG is a tight fit! A printed board will definitely free up some space as all the hookup wire will be replaced with traces on the board underside.

Second photo is a 256 color palette test from the VGA out side of my CGA->VGA converter project. I went with the standard VGA RRRGGGBB convention, which gives 8x8x6 for 256 colors. The DAC turned out to be really simple, with 8 resistors. Right now I'm using 5% resistors, but I'll change that out for 1% in the near future for better accuracy.

I realized when working on DAC, that I don't need an 8-bit ADC per channel. I only need two 3-bit ADCs for Red,Green and a 2-bit ADC for blue. So with that in mind I'm going to see if I can't use a R2R ladder & a couple transistors to build the ADC module, instead of specialized IC chips. If I can get that to work well with good results, then I'll be able to cut a good chunk out of the parts budget.
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

Unstupid

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #20 on: December 06, 2012, 09:30:47 pm »
If you can make these work as good as the SLG3000 then I'd buy some from you... I hate sending my $ to germany!  Plus shipping takes forever!

CraftyMech

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #21 on: December 07, 2012, 11:12:47 am »
If you can make these work as good as the SLG3000 then I'd buy some from you... I hate sending my $ to germany!  Plus shipping takes forever!

Exactly why I decided to build my own, I didn't want to deal with international shipping!

The SLG-3000 has more features, but I think the mini-SLG works great for standard/medium resolutions in a compact package. I have a couple prototype units that I mailed to two of our fellow forum members, and I'm looking forward to the feedback. The next step would be to get pcbs made, and I would be ready to offer up units for sale. With Christmas rapidly approaching, it is looking early January when the mini-SLG would be available.

What kind of setups would you be looking to use the mini-SLG in?
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

Unstupid

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #22 on: December 07, 2012, 01:28:37 pm »
If you can make these work as good as the SLG3000 then I'd buy some from you... I hate sending my $ to germany!  Plus shipping takes forever!
What kind of setups would you be looking to use the mini-SLG in?
Looking to build a whole bunch of these, in different configurations...  10" screens that run at 640x480.  Want to make a whole arcade of little machines running classic games:

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #23 on: December 07, 2012, 03:39:50 pm »
I'd be in for a couple, depending on price. At least one for sure.
***Build what you dig, bro. Build what you dig.***

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #24 on: December 07, 2012, 03:41:14 pm »
If funding is an issue maybe throw it up on kickstarter  ;)

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #25 on: December 08, 2012, 01:02:19 am »
I'd be in for one or two as well.

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #26 on: December 08, 2012, 09:30:46 am »
CraftyMech,

that's fantastic news about your CGA to VGA converter project ! In all honesty - a community based 15 to 31khz converter board is what I've been waiting for since ages. I'm running http://retrogaming.hazard-city.de/ which you might know and I've been through all the available converter solutions.

I'd very much like to offer you any assistance I can, any promotion and a full featured preview or review on my page. If you need any input, also please don't hesitate to ask !

I can't see any way to contact you other than here, but feel free to drop me an email or contact me otherwise! Would be great to get in touch with you !

Tobias / Fudoh

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #27 on: December 08, 2012, 09:39:23 am »


Did you just join from shmups forum?

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #28 on: December 08, 2012, 09:45:45 am »
I sure did, yes!

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #29 on: December 08, 2012, 09:52:47 am »


Glad my link helped you :D

There's a monitor/tv section here i'm sure you'll love.

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #30 on: December 08, 2012, 10:01:43 am »
I'm really liking of what I see here! Looking forward on news about VGA signal converting!  :)

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #31 on: December 08, 2012, 03:12:17 pm »
Thanks everyone for the interest in the mini-SLG and CGA->VGA converter! I'll be finalizing the mini-SLG design by early next week, and will order the printed circuit boards. Based on the interest level I'm seeing in this thread, I'm shooting for an initial run of around 20-30 units. Once I know the parts cost I'll post the price, I'm shooting for around $15.

that's fantastic news about your CGA to VGA converter project ! In all honesty - a community based 15 to 31khz converter board is what I've been waiting for since ages. I'm running http://retrogaming.hazard-city.de/ which you might know and I've been through all the available converter solutions.

Hey Tobias, I took a look at your website and you really have a lot of great information there on a ton of converter products. I'm going to have to set aside an hour just to read through the reviews. I'm sure I'll have some questions that I can pick your brain about, I'll send you a PM with my email address.
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #32 on: December 08, 2012, 06:26:41 pm »
$15 would be a nice price point.
I have one of bootsector's SLGs (which I really like) so I'm not currently in the market for one.  I always like to know what options are out there for future builds so I'll keep an eye on this thread.

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #33 on: December 08, 2012, 08:38:36 pm »
At a price point of $15, I'd be in for three. Thanks for doing this.
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Yvan256

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #34 on: December 09, 2012, 11:02:36 am »
Looking to build a whole bunch of these, in different configurations...  10" screens that run at 640x480.  Want to make a whole arcade of little machines running classic games:

You have a source for 640x480, 10" screens? Where? How many left? Which input(s) do they have? How much are they?

Unstupid

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #35 on: December 09, 2012, 11:47:53 am »
You have a source for 640x480, 10" screens? Where? How many left? Which input(s) do they have? How much are they?
Don't want to derail this thread so I replied on my thread over here: http://forum.arcadecontrols.com/index.php/topic,128428.0.html

BTW if you make the slg available for $15 I'm in for at least 10.

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #36 on: December 11, 2012, 10:11:32 pm »
The mini-SLG is a pretty neat little device. Haven't messed with it a whole lot yet, but so far I like it. Here's MAME on a 19" HP LCD at 1024x768...

                                                            BEFORE


                                                             AFTER


I'd say this is a definite must have for any cab with an LCD (60-in-1s 'n such).

I fiddled with the pot, but didn't notice any difference. However, the mini-SLG was on the back of my computer under my desk. I'll have to dig out another VGA cable so I can adjust the pot while watching the monitor.

Great work CraftyMech!


EDIT: Pics fixed. After seeing this difference, I need to make a dedicated vertical cab... :'(

Here's what scan lines look like the wrong way vs. the right way... :-[
« Last Edit: December 11, 2012, 10:42:04 pm by Nephasth »

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #37 on: December 12, 2012, 01:14:53 am »
That's awesome, and great price too.

@ Nephasth: Could you post a pic of it running at 640X480?
« Last Edit: December 12, 2012, 01:21:43 am by RRR »

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #38 on: December 12, 2012, 01:23:06 am »
Thanks for posting up the pictures Nephasth! I did not do that much testing at 1024x768, so I'm glad to hear you liked the results with a vertically orientated monitor.

When you get a chance, check out the mini-SLG for your 60-in-1 board. One thing I tried to do with my design was to not use straight black scanlines. I felt that on the low-res games (Pac-man, etc..) the detail suffered and felt even lower res. So I kept the scanlines at around 15% intensity and found that the scanline impression was still quite nice, while not degrading the game resolution. Let me know what you think!

As for the pot adjustment, it controls the intensity of scanlines for the Red channel, versus the Blue channel. The effect will be more pronounced on low-res games, at 640x480. I've actually been thinking about dropping the pot from the design. As you discovered, it is hard to judge unless you are looking right at the monitor, and the effect is more pronounced on low-res games, and not so much at higher resolutions. Plus I do like the idea of the mini-SLG as a true plug-and-play adapter, with no switches or adjustments to worry about. Instead, I would use a fixed resistor to strike a good balance between the R,B signals.
 
« Last Edit: December 12, 2012, 01:36:40 am by CraftyMech »
"mini SLG" - VGA scanline generator
900+ sold, $29 + shipping
http://www.paradisearcadeshop.com/scan-line-generators/1253-mini-slg.html

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Re: Side Projects: "mini" SLG & CGA->VGA converter
« Reply #39 on: December 12, 2012, 07:41:46 pm »
Looks great with a 60-in-1! It's really hard for me to capture good pics, but it looks much better in person. Not sure exactly what the resolution is that the board puts out, but it's lower than 1024x768. These were on a 15" Samsung.

No mini-SLG:


mini-SLG (this one did a good job of showing th scanlines on the fading power pellet):


Galaga ship - no mini-SLG:


With mini-SLG:


Quick shot of the enemies (the top row showed up best in the pic):


Thoroughly impressed CraftyMech! :applaud:

Have you tested it with a Gnobes converter yet?

Oh yeah, I was able to adjust the pot while watching the screen with the 60-in-1. I'd say keep the feature. I was able to find a preference with it.
« Last Edit: December 12, 2012, 07:44:51 pm by Nephasth »

  
 

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