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viletim
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Post Posted: Sun Sep 17, 2006 9:16 am
hello!

I found out about this thread a few months ago through segasonicfan's webpage (hi ssf). I thought: wow, that's really interesting, I'll have to try it out sometime... A few days ago seemed a good time. So I read through the entire thread and was a bit disappointed that the current design was only suitable for some Game Gears. A search of my beadroom turned up three GGs. Two 1 ASIC models -- one working ok, the other is mostly ok but very corroded and the top 1/5th of the screen doesn't seem to work. One 2 ASIC model -- put in a game, turn it on, the screen slowly fades from black to white and then the power shuts off...ick.

Right..well...long story short, I've come up with a good design for the 1 ASIC Game Gear. I've uploaded the circuit diagram and a few screenshots to members.optusnet.com.au/eviltim/ggrgb/ on the http protocol. I found it hard to photograph the monitor, there are two shots of the sonic title screen. One is overexposed (the monitor isn't really blooming on the white bits) and the other has the white balance way off (so colours are wrong).

Tech stuff:
This design is basicaly an elaboration on what xavier was suggesting with the 74HC4017. It uses a "counter" to divide the 32MHz master clock (is that what you call it?) into three 5.36MHz sub-pixel dot clocks which load the 4-bit colour data into three octal flip-flops. I use counter in inverted commas because it's really a shift register pretending to be a decimal decade counter. One problem I had was figuring out how to syncronise the data so red, green and blue data go to their respective DACs. What I've done is used the short H-Sync pulse (it goes to the LCD) to hold the counter in clear mode for a few hundred nS after every scanline.

This part of the circuit needs to use fast logic. I tried a 74HC164 to begin with but it didn't work very well. Normaly the shift register counts 6, when it gets to the 6th bit it pulls it's own clear line low through the NAND gate and resets itself all in time for the next pulse from the 32MHz clock. What happens when the hc chip is in the driver's socket is that when bit 6 comes along it tries to clear itself and brace itself for the next pulse. But it's too slow, it misses the next pulse because the hc164 takes too long to clear itself. Now I have a divide-by-7 instead of a divide-by-6. I could get dodgy and configure the IC for a divie-by-5 but I don't really want to rely on this "feature".

I haven't tried to substitue a HC02 for the F02. I'll try it sometime soon but I think an F is required for reliability.

The video DAC in xavier's ggtv25nm.jpg is only suitable if using AC574s (they can sink/source 25mA from each pin I hear!) for regular old HC574s this DAC is quite poor. The problem is that HC logic can only source 4mA per pin (while maintaining a guarenteed logic level) and even then then voltage is about 4.5 instead of 5v. So forget about 15mA for D0!

My DAC uses the same resistor numbers as xavier's but an order of magnitude higher in value. Then a two cascaded emitter folowers to drive the TV/Monitor. All resistors in the DAC are 1% metal film type. The amplitude of the video is 0.7v peak to peak into a 75 ohm load (1.4Vpp unloaded). This is controlled by R5 which can be changed if driving an arcade monitor or something else non-standard.

There is lots of noise on the +5v rail inside the game gear. To prevent the power supply noise from getting into the video signal I filter it out with a pi filter made from L1 and C1. They are just parts I picked from the junk box. I might experiment later to find out the lowest value inductor required.

This circuit has been tested on all of one whole game gear so I don't know how universal it is. It will work on all 1 ASIC versions so long as the H-SYNC pulse is in EXACTLY the same place every time. I suspect it will also work on the 2 ASIC model aswell with little or no modification (no RC delays :)).

And, finaly, having just measured it, I should mention that the circuit draws 75mA (92mA if I use the RGB enable line) of current while displaying a fully white screen. It'll probably draw a lot less if I don't connect it to a TV.

I suppose the next step is to make it out of all SMD parts on a little PCB that will fit inside the GG. There's lots of space under the cartridge port, I reckon I could fit two...

(*MOD* Edited by moderator, adding linked files as attachment to the post)
ggrgb_circuit.png (32.27 KB)
ggrgb_circuit.png
hardware.jpg (128.51 KB)
hardware.jpg
ingame.jpg (129.46 KB)
ingame.jpg

 
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Post Posted: Sun Sep 17, 2006 12:11 pm
Wow! This is awesome news.
You must be the same viletim as on the gamesx forums :)
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Post Posted: Mon Sep 18, 2006 2:10 pm
Today I had a look through a 'digital systems' textbook. Reading through the different types of counters and found my shift register counter in there :). I read that by feeding an inverted version of the last output (that I need) to the input of the shift register (instead of tying the input high) a 'Johnson counter' is born. I can make a MOD-6 Johnson counter with 3 flip-flops which is something like a divide-by-2 and a divide-by-3 rolled together.

I'm pretty sure this is exactly how the official sega unit operates. It uses a '175, which contains four flip-flops, as a MOD-6 counter and a '00 which is used to clear/synchronise the counter (possibly with the same H-Sync pulse I use).

I don't have time atm to try this out but I hope to get a chance within the next few days.

I also made a mistake with the data lines on the circuit diagram. They're labled D0-D3 (MSB-LSB) when they should be D3-D0 (MSB-LSB). No big deal...
 
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Post Posted: Mon Sep 18, 2006 3:52 pm
Quote
I'm pretty sure this is exactly how the official sega unit operates. It uses a '175, which contains four flip-flops, as a MOD-6 counter and a '00 which is used to clear/synchronise the counter (possibly with the same H-Sync pulse I use).


It's great that somebody has figured this out. I always wondered how Sega's GGTV really worked.

So the idea is that each of the red, green, blue latches are clocked at 5.36 MHz, and the ordering of which one gets clocked is done modulo 3? (green, red, blue repeating for each pixel) Then /HSYNC is used to reset it back to green at the start of each line?

What software did you use to make the nice looking schematic, btw?
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Post Posted: Wed Sep 20, 2006 3:08 pm
I've tried it out and can report that the sega-style circuit works as expected. I've uploaded a new diagram (version B) to /ggrgb. No more fast logic required, it's 74hc all the way through. The 74hc175 doesn't seem to be very common but fortunately it's possible to make the equivalent from a pair of 74hc74 ICs. Simply connect all the pre-set inputs to +5v, tie all the clock lines together, and do the same for the clear lines.

I was thinking some more about this so called H-sync line that goes into the LCD on pins 9, 29 and 49 (to the thee column drivers)...Why does it exist? My understanding of the way LCDs operate may not be the best but one this I do know is they don't need horizontal synchronisation. I cut the trace between the LCD and ASIC and connected LCD end to +5v/ground. It seems to be some kind of line latch input, on a negative edge transition the lcd latches the current line into place. I tied it to ground and it coppied one line all the way down the screen. If I tie to +5v then it everything appears normal, but on closer inspection some things don't look quite right...for example on a dark to light screen fade the three columns seem to fade out of sync with each other. Anyway, this signal, I'll call it /HLATCH for now, is definately THE signal to sync the counter.

I've currently tested this on two single ASIC game gears (USA VA1 837-9024 -- one made in Japan, the other, Taiwan). My two ASIC game gear is in bad shape at the moment so I'll have to wait for somebody else to try that out.

[Admin: added diagram as attachment]
ggrgb_circuit_ver-b.png (32.58 KB)
Circuit diagram
ggrgb_circuit_ver-b.png

 
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Post Posted: Wed Sep 20, 2006 3:13 pm
oh..nearly forgot, Charles, I used Qt-BSch 0.11 to draw the circuit.
 
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Post Posted: Wed Sep 20, 2006 3:45 pm
I know even less about LCDs, but some of the models with similar specs/numbers to the GG's screen (UC-320) on Citzen's website ought to have similar characteristics. I see plenty of HSYNC mentions there, eg. in the USC-220.

I'm suspicious that the LCD supports composite input, since several of their LCDs support dual RGB/composite inputs, and that the TV Tuner utilises this, but it's pure speculation.
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Questions Answered...
Post Posted: Wed Sep 20, 2006 7:33 pm
Hey everyone,
Glad to see we finally have a version for the 1-asic game gear. Viletim, Xavier, and all others who helped finish this, you RULE. Its good to see that people out there can stick with a project that can make people enjoy there old out-dated systems in a whole new light. Again, great job to all of you.

Now for my contribution, I have been reverse engineering my $1500.00 developers game gear and have seen some interesting things that I didnt expect to find, but here is the very basics for now.

IC-1 - 315-5242 - Sega's Custom video DAC
IC-2 - CXA1145 - Sony's RGB encoder
IC-3 - 74HC175 - Quad-D Flip/Flop
IC-4 - 74HC175 - Quad-D Flip/Flop
IC-5 - 74HC175 - Quad-D Flip/Flop
IC-6 - 74HC00 - Quad 2-Input NAND Gate

If we would have known this sooner it would have greatly increased the time it took to complete these two versions.
The circuit I have been working on is basically a match to segas with the exception to the 315-5242 IC, I opted for an Analog Devices ADV7120 instead, its cheaper, $10.00 compaired to $90.00 for the sega IC, more advanced, it will suit this application just great, and most importantly, its easy to get ahold of.
I have no need to finish mine since this project has been cracked but will anyways since I have way to much time and money involved to just quit. I will keep everyone informed as always on what my findings are.
Once again, great job to everyone that helped make this dream a reality.

MOD-MAN...
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Post Posted: Thu Sep 21, 2006 12:18 pm
So there are three HC175s???....things just got a bit foggier. I was going by a photo I got from some website and didn't even consider that there might be more chips under the DAC. I just assumed Sega's magic DAC could latch the signal itself.

If there are three quad flop-flops then there's little doubt that they are being used to latch the R, G, and B data before it goes to the DAC. Which leaves nothing but the lowly hc00 to handle the clocking of the three latches. No counter scheme...just using combination of various signals already available on the board to latch the data like Xavier's circuit does. What do you think about that, Mod-Man?

Would it not be too far-fetched to conclude that Sega's own RGB board could not work with the single ASIC Game Gear?

Anyway, I've drawn up a logic diagram that should explain how the counter works (since it's hard to understand from the circuit). It shows what happends after each 32MHz clock pulse. The designators/pins bear no resemblance to those on the circuit diagram, and the upward arrow indicates something is triggered here. It starts on the tail end of a HLATCH pulse (during which all Q's are set to 0 and all /Q's are set to 1). When that finishes (and not sure of the exact place in relation to the RGB data, just an educated guess, it's too fast for my oscilloscope), the first positive going clock pulse will shift the data to the right. All started at 000, it's now 100, next clock pulse it's 110, then 111, 011, 001, 000, 100, etc. Mr. Admin, the diagram is in the usual place :).

Maxim, the LCDs on the citizen website are LCD modules, which is made up of an LCD pannel + a controller board to convert analog video to digital, LCD-like, video. The LCD in the Game Gear doesn't have such a controller board, the ASIC drives the LCD directly. So whatever the TV tuner outputs, you can be sure it's no analog form of signal because there is no analog inputs on the cart. port or the ASIC.
ggrgb_logic.png (9.28 KB)
Logic. You could just register and do this yourself, y'know...
ggrgb_logic.png

 
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Post Posted: Thu Sep 21, 2006 1:40 pm
Quote
You could just register and do this yourself, y'know...
lol

Still, nice work on the GGTV. Maybe I'm going to do that to my GG.
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Post Posted: Thu Sep 21, 2006 2:11 pm
I'd love to see a step-by-step guide for people who aren't so skilled, maybe on the same level as the SMSReader instructions, maybe on the wiki?
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Post Posted: Fri Sep 22, 2006 1:41 pm
Quote
Glad to see we finally have a version for the 1-asic game gear. Viletim, Xavier, and all others who helped finish this, you RULE. Its good to see that people out there can stick with a project that can make people enjoy there old out-dated systems in a whole new light. Again, great job to all of you
.
Quote

Once again, great job to everyone that helped make this dream a reality.

MOD-MAN...


Couldn't have said it better, MOD-MAN. This has been a dream of mine since the day the GG came out.

Since it now works on 1ASIC GGs, wouldn't the only thing that changes on the schematic be the pin numbers on the chip that the wires connect to? I don't see that accounted for on the schematic...

It would rock if someone made some PCBs and do-it-yourself kits for these. The wiring is the hardest part for me. I can throw things on a board and solder easily, though. ;)

But for now, I'm just happy as hell this was cracked!


MOD-MAN, I"m definitely interested to hear what else you have to say about Sega's mod board. Any chance of a schematic of that when you finish? I know, I ask too much....I just alwyas wondered about it. :) So did you have to remove the rubber casing from it? How'd you do it?

-Rob
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Post Posted: Fri Sep 22, 2006 3:23 pm
Quote
So did you have to remove the rubber casing from it? How'd you do it?


The rubber (epoxy) casing is only on the the hybrid module that contains the DAC. The actual nuts & bolts of the converter are the chips MOD-MAN mentioned.

The DAC itself contains a 16-bit latch and some resistor ladders, but that's really it. Because it latches all it's inputs when clocked, it works as the final (missing) '175 which is why the Sega GGTV unit only has three of them (one to generate the clock signals, one to latch red, one to latch green, and then the DAC latches blue as well as the other two).

I think that accounts for everything.
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Post Posted: Sat Sep 23, 2006 9:44 am
viletim wrote
If there are three quad flop-flops then there's little doubt that they are being used to latch the R, G, and B data before it goes to the DAC. Which leaves nothing but the lowly hc00 to handle the clocking of the three latches. No counter scheme...just using combination of various signals already available on the board to latch the data like Xavier's circuit does. What do you think about that, Mod-Man?


Sounds right, for obvious reasons, I am taking extremely great care in reverse engineering my developers game gear, mainly for the fact that it basically cant be replaced, I want it to look untouched when done, and what I paid for it. So, as i get deeper into where the traces and everything goes, I will learn more of what the engineers were thinking when they designed it, its just taking me a while.

viletim wrote
Would it not be too far-fetched to conclude that Sega's own RGB board could not work with the single ASIC Game Gear?


Actually, thats a good point, I have no reason as of yet to assume that it would not work, all the signals it pulls from the 2-asic game gear are readilly available on the 1-asic version I think, I would have to check my notes at this point. I dont want to damage anything on my sega board so I will not be trying it out, but as soon as my replacement version is done, I will test it on both, but I still believe it will work with all of them. I also think that your version might work on both because of the signals you use to pull from are all available on both systems, unlike Xaviers, his used signals not found in both versions, although his deffinatly works great, its just not universal without a bit of rework as you proved.

viletim wrote
The LCD in the Game Gear doesn't have such a controller board, the ASIC drives the LCD directly. So whatever the TV tuner outputs, you can be sure it's no analog form of signal because there is no analog inputs on the cart. port or the ASIC.


The TV tuner is an incredable piece of equipment, and your right, no analog outputs. From what I can tell in my schematics is that it takes the analog video signal (R, G, B) and inputs it into a custom video ADC that outputs the information directly into the data lines of the cartridge port. Kind of like using the TV tuner as a continually updating cartridge without inputs, only outputs. That would explain why you cant use the tuner when using video out from the game gear, screen is all scrambled, this leads me to believe that the tv line on the cartridge port in some way switches the asic into a different mode to accept a different encoding sceme, and then controls the LCD and bypasses all the other areas of the asic that would be used for games. Or does that sound to unrealistic?

rbudrick wrote
It would rock if someone made some PCBs and do-it-yourself kits for these.


Once I finish my version, I plan on having a professional board built so it looks like it is supposed to be there (I have a smoke shelled game gear I plan on putting all my mods in). When I have this done I can easily order a large set of extras, I have plenty of parts to put together alot of kits or make some ready built boards, the only thing I dont have large quantities of is the ADV7120, but that is simple to fix. Just give me a few more months to finish mine as it is not the only thing I do in life and I will put something together for people.

rbudrick wrote
Any chance of a schematic of that when you finish? I know, I ask too much....I just always wondered about it. :)


Not asking to much, just again, give me time. I will try and get a schematic together, it just may not be to pretty, I am good at reading them, not writing them. my methods of note taking are a little out of the ordinary.
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Post Posted: Sun Sep 24, 2006 3:25 pm
Charles, that makes perfect sense. I didn't think about the DAC's own latching input.

I did some more work on this today. Firstly, I repaired my 2 ASIC GG and made sure it's compattible with the circuit (it is). I've also discovered the reason why there is so much noise on the power rail. It's because the SMD capacitors that are ment to filter is are going bad and some of them are even leaking electrolyte. On one of them I replaced all the capacitors with new ones and noise on the power rails is gone, no need for a filter on the video DAC circuit.

Next, I went about building another board, this time using parts only available from a local shop (1x hc04, 2x hc74, 3x hc374). These parts are extremely common and should be easy for anyone to buy localy. I'll redraw a 'final' circuit using these. Also the board is small enough to fit in the space under the cartridge slot. The hc74s and hc374s were stacked on top of each other to save on board real estate. It's a good method and greatly reduces the ammount of wiring needed to be done too. I'll try to write up some instructions for people to build this one in the next few days.

I was thinking that this circuit could likely fit well into a CPLD (programmable logic). That would be ideal for anyone wanting to make a kit or something. A CPLD would have the same current sink/source abilities as 74AC (24mA) logic so the dac can be reduced to just four resistors. There would be plenty of room for a small PCB with a 44 pin PLCC package, 12 SMD resistors, an AD725 NTSC video encoder, etc.

I've never tried using a programmable logic before but I'd like to try it sometime. Though I probably won't get around to this anytime soon...

Quote
That would explain why you cant use the tuner when using video out from the game gear, screen is all scrambled, this leads me to believe that the tv line on the cartridge port in some way switches the asic into a different mode to accept a different encoding sceme, and then controls the LCD and bypasses all the other areas of the asic that would be used for games. Or does that sound to unrealistic?


Perhaps the signals between the two ASICs that Xavier operate differently (or not at all) when in the TV mode? I don't have a TV adaptor (or even a master sys adaptor) so I can't try it.
fitinside.jpg (83.83 KB)
fitinside.jpg

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Post Posted: Mon Sep 25, 2006 3:30 pm
Quote
rbudrick wrote:
It would rock if someone made some PCBs and do-it-yourself kits for these.


Once I finish my version, I plan on having a professional board built so it looks like it is supposed to be there (I have a smoke shelled game gear I plan on putting all my mods in). When I have this done I can easily order a large set of extras, I have plenty of parts to put together alot of kits or make some ready built boards, the only thing I dont have large quantities of is the ADV7120, but that is simple to fix. Just give me a few more months to finish mine as it is not the only thing I do in life and I will put something together for people.

rbudrick wrote:
Any chance of a schematic of that when you finish? I know, I ask too much....I just always wondered about it. :)


Not asking to much, just again, give me time. I will try and get a schematic together, it just may not be to pretty, I am good at reading them, not writing them. my methods of note taking are a little out of the ordinary.


Awesome...I've waitied this long, I can certainly wait a little longer. I kind of blew up my rare 2 ASIC GG when I went to build the older circuit (Xavier's, iirc). Or at least, the screen doesn't work. So, I can't wait to see your PCB and test it out.

-Rob
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Post Posted: Fri Oct 06, 2006 8:43 am
I've made a guide to assembling the circuit.
http://members.optusnet.com.au/eviltim/ggrgb/ggrgb.html
Let me know if you think I should elaborate on any part of it.

Here are various screen shots (I decided not to link to them in the above page due to bandwidth considerations)
http://members.optusnet.com.au/worthair/ggrgb/
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Post Posted: Fri Oct 06, 2006 9:53 am
That's really good, there's a few typos (DE9?) but it all seems sensible. Somebody needs to work through it to see what needs elaborating, but I can't help thinking that resistor spaghetti part (image attached below) could have been broken down a little bit. The "ground floor/first stor(e)y/second stor(e)y" diagrams seem clear enough once you notice the grey circles, though; you just could've photographed the whole lot component-by-component (or maybe every 3 components or so) so people can compare step-by-step. Then again, as you said, this isn't a "my first soldering iron" project.

Regarding the screenshots: do you get any noise in the VBlank or inactive image area? I think most GG games wait for the "natural" VBlank at line 192 (instead of using H-ints to turn the screen off after the displayed section), so it might be off-screen on your TV, but certainly PAL SMS games tend to have a few pixels of noise in the "border" colour when the VDP is being thrashed during the VBlank. I'm wondering if the GG VDP performs better in this respect, since I can't see any such noise on your images.
build_boardstart.jpg (18.79 KB)
Resistor spaghetti
build_boardstart.jpg

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Post Posted: Fri Oct 06, 2006 7:06 pm
Maxim wrote
That's really good, there's a few typos (DE9?)


The D specifies D-sub connector, the letter after that specifies the size of the connector and the number the number of pins. So a Sega joystick port is a DE9, whereas a connector like the parallel port on your computer, but only populated with nine pins, would be a DB9.
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Post Posted: Fri Oct 06, 2006 11:06 pm
http://en.wikipedia.org/wiki/DE-9_connector

I stand corrected. It's just one of these things everybody says wrong, I guess :)
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Post Posted: Fri Oct 06, 2006 11:32 pm
Maxim wrote
http://en.wikipedia.org/wiki/DE-9_connector

I stand corrected. It's just one of these things everybody says wrong, I guess :)



Consider my mind blown.
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Post Posted: Sat Oct 07, 2006 12:52 am
Here's the annoying list of actual typos:

"data is send serially"
"delelopment"
"through and adjacent hole"
"on it's power supply rails"
"SMSPower"

I may start using "delelopment" myself.
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Post Posted: Sat Oct 07, 2006 6:06 am
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In slower, less graphical games such as lemmings there isn't any noise in the border area

Lemmings actually hammers the VDP pretty hard, since it's redefining VDP tiles on the fly (and reading them back from VRAM a lot) to simulate bitmapped graphics. The only sprite in that game is the cursor, the lemmings are all drawn onto tiles at runtime.
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Post Posted: Sat Oct 07, 2006 12:44 pm
Here's the annoying list of actual typos:

"data is sent serially"
(should be data are)

See, I can be even more anal than Maxim! ;-D
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Post Posted: Sun Oct 08, 2006 12:30 pm
viletim wrote
Quote
In slower, less graphical games such as lemmings there isn't any noise in the border area

Lemmings actually hammers the VDP pretty hard, since it's redefining VDP tiles on the fly (and reading them back from VRAM a lot) to simulate bitmapped graphics. The only sprite in that game is the cursor, the lemmings are all drawn onto tiles at runtime.

Please don't overwrite my post and replace the text with your own. If you want to contribute then make a NEW reply!
 
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Post Posted: Sun Oct 08, 2006 4:17 pm
viletim! wrote
viletim wrote
Quote
In slower, less graphical games such as lemmings there isn't any noise in the border area

Lemmings actually hammers the VDP pretty hard, since it's redefining VDP tiles on the fly (and reading them back from VRAM a lot) to simulate bitmapped graphics. The only sprite in that game is the cursor, the lemmings are all drawn onto tiles at runtime.

Please don't overwrite my post and replace the text with your own. If you want to contribute then make a NEW reply!


Aargh, sorry! The "edit" button is right next to the "quote" button and I didn't realise I'd done that. Can you re-post what you said?
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Post Posted: Wed Oct 11, 2006 7:38 pm
http://www.mash-mods.com/products/Sega%20GameGear/ggtvblastI

Lol...you guys seen this? I let him know there is a much newer design.

-Rob
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Post Posted: Sun Dec 03, 2006 5:32 pm
My god, so much progress :-)
Congratulations for the new design!

About the DAC, you are right my first design was pretty primitive.
However in order to gain some place and reduce cost, I keep it but I replaced the old value by 1% 700ohm, 1,4K, 2,8K and 5,6K and removed the adjustment resistor.
Under un receptor impedance of 75ohm and with 74hct574, the currant consuption is really limited (13mA at full deflection) and it work in the correct RGB range (0 to 0,8V).

In other hand your DAC is far more "flexible" than mine ( basicelly it need a 75ohm RGB european TV set) your can easyli handle more exotic set.
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Post Posted: Thu Dec 14, 2006 8:20 am
Looks like I'll have something to do: building a TV adapter for the Game Gear.

Just one thing: SCART is rarely used in USA so... Is there a creative RGB+synch to S-Video or Composite adapter to go at the end of the RGB connections?

The only alternative is to take the SNES console out of the playable store demo station and use its SCART board with RGB monitor to play with Game Gear. That beast is by no mean small or light!!! The SCART to RGB board itself is about the size of SMS 1 console.

EDIT: what game gear do I have??? It looks like the single chip version but the part number doesn't match.My chip has the part number 315-5682. Yet this one works with the TV tuner so it is an early Game Gear model. I checked the other side of the board and found only one chip a RAM chip (256kbit probably)
315-5682.jpg (266.63 KB)
mystery_chip
315-5682.jpg

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Post Posted: Thu Dec 14, 2006 4:45 pm
A couple pages back I posted some commercial converters from RGB to Composite, or Svideo, or whatever. I hear the Keene one is the best, with the others not so good.

-Rob
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Post Posted: Wed Jan 10, 2007 6:07 am
Yeah, there are a ton of sources for RGB-> S-video/Composite transcoders. I actually have a couple extra and I would be willing to sell one of em if you're interested. You can also try building your own. See the Arcade Works website for pics of the encoders and how to build them: http://www.freewebs.com/segasonicfan

now the real reason I'm here...
I know this schematic won't be as important since viletim did all the great work on a 1 ASIC mod, but I worked really hard at improving the 2 ASIC schematic and I would like to hope that this is the best one available/easiest on the eyes. Hopefully someone will get some use out of it.

-Segasonicfan
ggschem.png (25.33 KB)
ggschem.png

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Post Posted: Mon Feb 26, 2007 4:42 pm
Just a bump. Still wanting to buy a prefabbed board and kit from someone (or totally premade, doesn't matter). :-) Just figured I'd check to see how that is progressing.

-Rob
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Post Posted: Thu Apr 26, 2007 12:06 pm
Hey Rob,
I will be back at my place upstate in 2 weeks where I have some 2 ASIC model GGs I can mod for ya :) I will also look into the 1 ASIC mod. Getting more excited about GG projects these days thanks to the new Playpal :)

-Segasonicfan
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Post Posted: Sat Jul 07, 2007 2:52 am
Okay I finally finished my first all inclusive GGTV :) It's for Rob so I won't get to keep it but at least I have pics to share!

http://i18.photobucket.com/albums/b134/Segasonicfan/GGTV3.jpg
http://i18.photobucket.com/albums/b134/Segasonicfan/GGTV2.jpg
http://i18.photobucket.com/albums/b134/Segasonicfan/GGTV1.jpg

inside pics:

http://i18.photobucket.com/albums/b134/Segasonicfan/GGTVinside1.jpg
http://i18.photobucket.com/albums/b134/Segasonicfan/GGTVinside3.jpg
http://i18.photobucket.com/albums/b134/Segasonicfan/GGTVinside2.jpg

The video output is outstanding in both composite and S-video thanks
to all the additional bypassing and power regulation I put in. I
included many extra caps on the power lines, 2 tantalum caps to bypass
the encoder, and a 100uh inductor to smooth out the +5v going to the
GGTV circuit (this was needed to remove oscillation within colors). I
also added a protection diode for peace of mind :)

I found the sync needed to be 200ohms terminated to properly work with the encoder. It isn't shown in the pics though because I added it later. I also made some tiny corrections to my schematic, turns out I had the RGB lines swapped again.

tis a shame I can't keep this beautiful system heheh. I bet Rob will enjoy the hell out of it though :)

-Segasonicfan
ggschem-1.png (25.36 KB)
ggschem-1.png
GGTV3.jpg (46.86 KB)
GGTV3.jpg
GGTV2.jpg (37.57 KB)
GGTV2.jpg
GGTV1.jpg (49.29 KB)
GGTV1.jpg
GGTVinside1.jpg (617.35 KB)
GGTVinside1.jpg

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Post Posted: Mon Aug 27, 2007 6:35 pm
SSF did an incredible job on this GGTV...you'd have to see it to believe it. It's a 17 year dream to own such a device, so I couldn't possibly be more happy with it. SSF did it for an extremely reasonable price and the quality is top notch.

Now if only my Lynx and Game.com connected to a TV. HAH!

-Rob
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Post Posted: Tue Aug 28, 2007 3:13 pm
i would love to have such a mod. playing my original gamegear on my tv in rgb sounds great.
you can say i have been tinkering around in the rgb mod scene for a while now. all my rgb modded children.
NES, SNES, N64, sega master system, genesis, saturn, dreamcast, turbografx, turbo duo, supergrafx,
jaguar, neo-geo, CDI, 3do, psx.
so far i have done all my mods on my own. but lately i have had little time to do such work.
is some one here still doing the game gear mods for hirer? segasonicfan?
if so that would be great could you please PM me more info.
selling some 3do rgb stuff i made hope that covers the cost for this :).

so any1 get the Rgb.... err um R mod done for teh VR boy yet? ; )
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Post Posted: Sat Sep 22, 2007 4:05 pm
SSF, can you repost the pics you posted of the unit? Looks like all the links are dead now. :-(

-Rob
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Post Posted: Tue Nov 06, 2007 7:14 pm
rbudrick wrote
http://www.mash-mods.com/products/Sega%20GameGear/ggtvblastI

Lol...you guys seen this? I let him know there is a much newer design.

-Rob

Can you link post or page with explanation of the new design?
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Post Posted: Fri Dec 07, 2007 10:32 pm
hi,
i want to build gg tv. but i don't understand a couple of things from the schematic.
1. what IC is that from the the box?
2. what value have the capacitators from the box?
by 'box" i mean the rectangle i added in the schematic.
thanx
circuit.png (25.3 KB)
circuit.png

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Post Posted: Fri Dec 07, 2007 11:18 pm
gorgyrip wrote
1. what IC is that from the the box?


That's the second half of IC3.

gorgyrip wrote
2. what value have the capacitators from the box?
by 'box" i mean the rectangle i added in the schematic.
thanx


I don't know, I haven't measured their value. Probably a few hundred picofarads.

I should also note that the circuit diagram has a 74HC574 for the data latch while the board design uses a 74HC374. I'm not quite sure how that happened. Both ICs are the same but have different pinouts.
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Post Posted: Sat Dec 08, 2007 12:03 am
thanx for the reply. i also used 74hct374.
but i stil don't understand about that IC.
the same pins are used on the left side of the schematic. the pins are exactly the same as in the first part of the ic.
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Post Posted: Sat Dec 08, 2007 2:34 am
Oh, so they are... another mistake. It should be pins 1, 2, 3 and 4 which are connected to +5v (or ground, or anywhere at all as this part of the IC is unused, just don't let them float).
 
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Post Posted: Sun Dec 09, 2007 5:07 am
Im attempting to build the 1 ASIC version for the first time now, hopefully it wont be too much harder (looks a good bit more complex).

Rob, all the pics are now on my new site www.freewebs.com/vgmods :)
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Post Posted: Sat Dec 22, 2007 5:01 pm
i almost finished this project, but i still need the 75 ohm resistors. i did't find 11 k rezistors and i used 10k + 1k.
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Post Posted: Sun Dec 23, 2007 2:04 am
gorgyrip wrote
i almost finished this project, but i still need the 75 ohm resistors. i did't find 11 k rezistors and i used 10k + 1k.


Use two 150 ohm in parallel.
 
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Post Posted: Sat Jan 19, 2008 3:41 pm
Hello there,

I've been following this topic since it's "birth" and I'm very happy to see it's nice development.

But now I have some suggestions/problems...

What can be done to make xavier's circuit compatible with an VGA monitor?
I have one available and we all know that they have much better quality than "regular" TVs.
The circuit will need an way to extract vertical and horizontal sync. Are these signals already available on the GG or is there only "composite" stuff?

good hacking!
ck
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Post Posted: Mon Jan 21, 2008 4:38 am
C3R14L.K1L4 wrote
Hello there,

I've been following this topic since it's "birth" and I'm very happy to see it's nice development.

But now I have some suggestions/problems...

What can be done to make xavier's circuit compatible with an VGA monitor?
I have one available and we all know that they have much better quality than "regular" TVs.
The circuit will need an way to extract vertical and horizontal sync. Are these signals already available on the GG or is there only "composite" stuff?

good hacking!
ck


The video signal timing is the same as a Master System - it's only suitable for TVs. The only way to connect the signal to a VGA monitor is to use some kind of digital upscaling device.
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Post Posted: Mon Jan 21, 2008 1:47 pm
what do you mean with "digital upscaling" ?
image resize? convertion to another signal frequency?
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Post Posted: Mon Jan 21, 2008 2:38 pm
To upconvert to VGA it'll need to have a device resample the video at a higher sync rate and resolution, hence it'll be digital (using an intermediate framebuffer). This page seems to cover the main points, but is a bit out of date. You can buy cheap(ish) devices for playing consoles on monitors, but the quality may not be great (beware scan doublers).
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Post Posted: Mon Jan 21, 2008 3:27 pm
Got it. Sorry but I dont know much about video signals...

Pitty some work has to be done about it, because it would be cool to have an GG / SMS directly connected to a high definition monitor :P
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