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Thread: RGB modded Snes mini, plan to use with GBS 8200, need advice.

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    Nameless One Michael Helgeson's Avatar
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    Default RGB modded Snes mini, plan to use with GBS 8200, need advice.

    I RGB modded my Snes mini here. RGB is tapped off of the encoder chip, as is sync, which was pulled off of pin 7. I wont be using the Snes AV out port, as I opted to do output jacks for each signal so I can make my own cable when the GBS arrives after I ordered one. Was planning to order a GBS 8200, and was trying to find out in advance if this combo will work fine first. I have read issues about the GBS having issues with different Jamma boards and game systems sync output, so figured I should ask. Is the GBS fine with flat out sync output though from the Snes mini, and if not, what extra work needs to be done to make them work together?

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    urusei yatsura Master of Shinobi lumclaw's Avatar
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    You may need 220uF capacitors. SNES RGB isn't meant to be connected raw.

    http://gamesx.com/wiki/doku.php?id=av:nintendomultiav

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    Nameless One Michael Helgeson's Avatar
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    This is what I did as far as tapping RGB and sync goes:


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    Creator of the Mega Amp Raging in the Streets Ace's Avatar
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    You might want to add an LM1881 to the GBS-8200 if you want to use RGB from a game console. I had difficulty using both Composite Sync and Composite video as sync directly into the GBS-8220, the two-output version of the same board, unless it was Composite Sync from one of my arcade PCBs.

    Something to note is that, if you haven't seen this thread on the SHMUPS forum, you can tweak the GBS-8200 and GBS-8220's scaler, the Tiva TrueView 5725, to properly handle 240p inputs and line-double them to VGA or Component at 480p. This will eliminate the deinterlacing artifacts the converter has. Only problem: you need to attach a Raspberry Pi to the converter. As you can see later in the thread, I plan on making this work with an AtMega328 programmed through an Arduino which can then be made into a standalone circuit that plugs into the converter and configures the chip at startup. Right now, the Raspberry Pi setup is somewhat messy, requiring you to boot the Pi and send your configuration data every time you power on the board.

    I should also point out I couldn't get the Super NES to work through an LM1881 with the Raspberry Pi configuring the converter. Why that is, I have no idea. It works fine with the stock firmware, so WTF?
    HATES ATGAMES WITH A PASSION


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    WCPO Agent Helder's Avatar
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    Interesting, so the Atmega would simply provide some configuration to the unit to accept 240p and line double? how far along is that coming along?

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    Creator of the Mega Amp Raging in the Streets Ace's Avatar
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    Currently stalled as I have done zero work with I2C on an AVR. I plan on writing the code using an Arduino Uno, then pulling out the AtMega328 and putting it on an separate add-on board which will plug into the GBS-8200 and GBS-8220 to configure the TrueView 5725 to work as a line-doubler. I actually plan on repurposing these boards into SCART to Component converters with integrated line-doubling so 240p incompatibility on HDTVs becomes a non-issue.

    Is there anybody with experience using I2C on an Arduino Uno who's willing to help me out?
    HATES ATGAMES WITH A PASSION


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    WCPO Agent Helder's Avatar
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    I wish I could help but I know jack shit about the avr language but I guess I should really set time to get into it since it seems to be rather useful.

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    Creator of the Mega Amp Raging in the Streets Ace's Avatar
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    I'm actually going to be working with the Arduino Uno board, which has a pretty easy to use programming language similar to C. I'll write the code with that, then use my Uno as a programmer to program the AtMega328 and put those chips on new boards made specifically to plug into the GBS-82x0.
    HATES ATGAMES WITH A PASSION


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    Wildside Expert fluxcore's Avatar
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    My PAL SNES works fine through the GBS-82x0 using a lm1881 sync stripper (and in 60Hz, since GBS-82x0 stock doesn't like 50Hz).

    Haven't tried using sync available from the video encoder.

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    Nameless One Michael Helgeson's Avatar
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    Quote Originally Posted by fluxcore View Post
    My PAL SNES works fine through the GBS-82x0 using a lm1881 sync stripper (and in 60Hz, since GBS-82x0 stock doesn't like 50Hz).

    Haven't tried using sync available from the video encoder.
    I ended up not needing a sync stripper for the Snes mini. Per what I posted on the PCEFX forums:

    Just to update this, GBS arrived and it worked with the Snes Mini fine. I added a 220uf cap to the sync line and that did not cause any issues, so basically everything is good to go. One issue, not really the Snes or GBS to blame, is that it cant lock on to the first Ranma 1/2 game. I knew though that this game may cause an issue. It seems to run in a strange resolution or does something to the Snes signal when its played. I cant really describe it, but you'd know it if you saw it running, that it doesn't look normal.

    I have tried it on two different Snes decks on LCD and CRT and it looks funny on either one. Via s-video the Toshiba lcd tv in my room coped with it better then the CRT tv in my sons room does, but yeah in general I suspected due to how the game acts that the GBS would not be able to display it, and I was right. The other 30 or so games I have all worked fine, including the 2nd Ranma 1/2 game, Bakuretsu Rantohen.

  11. #11
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker
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    You won't need an 1881 but it can make your life easier, especially if you don't have an oscilloscope to look at the signals.
    I got all my consoles working, using regular composite video, just with some passive components.
    You'll want a 220uF for all consoles, additionally a series potentiometer (use a nice one) of about 500 Ohm and one switcheable resistor of about 75 Ohm to Ground.
    Some consoles will work no matter what the passives are set to, some require the 75 Ohm to Ground and some get a nicer picture or more stability with a couple Ohms in series.

    @Ace:
    If I ever find the time, I want to add more features to the scaler. I'll still be using the rPi but your idea does sound nice for a more final product
    The programming work is probably no big deal, especially if you can use C or something comparable, that already provides I2C libs.

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    WCPO Agent Helder's Avatar
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    Using an oscilloscope what should the signal levels be?

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    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker
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    Helder:
    I have no idea, actually!
    I'd look up the specs and additionally search for any console specific stuff, like output circuitry shown in service manuals.
    Also needed is the correct measurement points and using the right probes.
    It's not a trivial thing ;p

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    Creator of the Mega Amp Raging in the Streets Ace's Avatar
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    The Arduino software has its own I2C library, and I managed to port SHMUPS user Mybook4's code made for the DigiSpark Pro over to the Arduino Uno to set up the GBS-8220 for pure line-doubling of 240p inputs. The code in question is here: https://github.com/mybook4/Digispark...er/GBS_Control

    This code with some adjustments could potentially be used on an Arduino Uno's AtMega328 to replace the GBS-82x0's on-board microcontroller so the TrueView 5725 scaler can take 240p properly. I will note, though, that the last time I tried using the GBS-8220 and GBS-8200 with this, it left a little to be desired, especially compared to the XRGB-1, which, while having some color reproduction anomalies (certain colors don't quite show up right), has a cleaner picture than the GBS-82x0. Then again, they're both completely different hardware and at a completely different price range, so it's probably not the best comparison, but my benchmark for line-doubling 240p to 480p over VGA is the XRGB-1.
    HATES ATGAMES WITH A PASSION


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  15. #15
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker
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    Quote Originally Posted by Ace View Post
    The Arduino software has its own I2C library, and I managed to port SHMUPS user Mybook4's code made for the DigiSpark Pro over to the Arduino Uno to set up the GBS-8220 for pure line-doubling of 240p inputs. The code in question is here: https://github.com/mybook4/Digispark...er/GBS_Control

    This code with some adjustments could potentially be used on an Arduino Uno's AtMega328 to replace the GBS-82x0's on-board microcontroller so the TrueView 5725 scaler can take 240p properly. I will note, though, that the last time I tried using the GBS-8220 and GBS-8200 with this, it left a little to be desired, especially compared to the XRGB-1, which, while having some color reproduction anomalies (certain colors don't quite show up right), has a cleaner picture than the GBS-82x0. Then again, they're both completely different hardware and at a completely different price range, so it's probably not the best comparison, but my benchmark for line-doubling 240p to 480p over VGA is the XRGB-1.
    Yea, it's actually 10 times as expensive. I would hope that it comes with finely tuned filters

    The Gonbes probably does better 240p filtering, if only someone discovered the right switch or hardware modification.
    I simply don't have the time to do the software research now. Register definitions and tools are available.

    The task would be to go over the docs, find some interesting flags, and try them out (using modified setting files in gbs-control).

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