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Thread: Need answers on possibly resetting Genesis with controller, while in SMS mode.

  1. #1
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    Default Need answers on possibly resetting Genesis with controller, while in SMS mode.

    I'm using the Arduino Nano chip, I have it installed in my VA6 Genesis, it is only setup to allow for in-game-reset with a controller. I'm also using the Mega Everdrive X7 flash cart.

    I looked up information about SMS mode from "db electronics", and it mentions cartridge pin B27 which is the soft reset gets changed over to GND when in SMS mode, and mentions that cartridge pin B2 is the master reset. So I tried soldering a wire from 2 different reset points near the reset button on the Genesis, to pins B27 & B2 one at a time, and was unsuccessful in resetting the system via the contoller in SMS mode.

    If anyone is familiar with the script "megadrive++" and know of this mod, would any of you know via modification if it's possible to reset SMS mode with this mod I'm using?

    Thanks!
    Last edited by infidelity; 01-12-2020 at 12:00 PM.

  2. #2
    Raging in the Streets Sik's Avatar
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    Sounds like you changed the Reset button itself instead :​P

    Pulling low on B2 is akin to pressing the Power button (i.e. resets everything). It should work if you're doing that right, though if you tie that directly to the Reset button you'll end up being unable to soft reset with Mega Drive games (may want to add some sort of switch to handle this, assuming you don't want to do something more complex like adding an OR gate). As for controller-based mods, no idea, would need to look more carefully at how it achieves that.


    EDIT: wait, you mention a chip, so you probably can do /MRES = (/M3 OR /VRES) AND /MRES if you really want :v (assuming I got the logic right)

    How is the controller input being detected though? Note that Master System games won't be toggling TH on the controller so A and Start will not show up in the port (if you're trying to sniff it that way, you're in trouble).

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    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    I dont know how to write the language for the script used in the nano board, but when in MD mode I'm able to reset via the rest button on my genesis, and via button combination on my controller.

    Then when I SMS mode, my reset button on my genesis still functions properly, but I lose the ability to reset via the controller. I thought MAYBE the start button & A button are disabled via SMS mode, but I have the wires soldered from the control port directly to the nano board, so my thinking is that the board is reading the inputs BEFORE the SMS mode has a chance to read the control port. Idk if my thinking is incorrect on this.

    When I tried the B2 cartridge pin, and soldered a wire to one of the 2 reset points on the bottom of the motherboard, the system was stuck in a reset loop when on SMS mode (at least from what I could see on screen, from black to semi-black over and over every 1.5 seconds)

    Edit: just saw your edit. Yes I'm trying to still use Start & A on my genesis controllers

  4. #4
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    https://github.com/SukkoPera/MegaDri...vePlusPlus.ino

    This is the script that I'm using on the nano board

    https://m.imgur.com/kqqgauM

    This is not my board, but I'd you look where the wires are for reset in/out, those are the locations where I added an additional wire to goto cartridge pin B2, tried each of those points one at a time.

    Hoping my wish will work somehow.
    Last edited by infidelity; 01-12-2020 at 12:49 PM.

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    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    Quote Originally Posted by infidelity View Post
    ...
    and mentions that cartridge pin B2 is the master reset...
    B2 is connected to the WRES line, which is the same of the reset button. The purpose is to allow a cartridge to send a reset signal, like if the reset button was pressed.
    In the MD there are two reset lines, one for the MD stuff, VRES, and the other one for the SMS stuff, ZRES.
    When the MD is in SMS mode, VRES is hold down, to disable the 68k. And ZRES was released to allow the Z80 to work.

    In the normal operation, the is one IC which is sensing the main reset line WRES. When the reset button is pressed or a cartridge send a reset signal through B2 this IC set the reset on both VRES and ZRES, resetting the entire console.

    On the SMS mode you can't reset the console by sending a reset signal on B27, because B27 is always low.
    And send the reset signal on B2, is exactly the same thing of pressing the reset button.
    Last edited by majinga; 01-12-2020 at 01:18 PM.

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    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    Quote Originally Posted by infidelity View Post
    ...
    Then when I SMS mode, my reset button on my genesis still functions properly, but I lose the ability to reset via the controller. I thought MAYBE the start button & A button are disabled via SMS mode
    I suspect this. The MD pads are back compatible with the SMS, same pinout. SEGA managed to have more buttons by adding a pulse singal, the pad send a different set of buttons at every rise or fall of the signal (if i remember correctly).
    In the SMS mode this signal can be stuck on HIGH which allow only the B and C buttons to operate. B and C are the same of the buttons 1 & 2 on the SMS.
    So the micro was never able to get the proper trigger combo.

    When I tried the B2 cartridge pin, and soldered a wire to one of the 2 reset points on the bottom of the motherboard, the system was stuck in a reset loop when on SMS mode (at least from what I could see on screen, from black to semi-black over and over every 1.5 seconds)
    ...
    That's because you soldered also on B27 which is always low, this keep the console in reset.

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    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    The only way to fix this is change how the micro operate. I was thinking about an easy solution. Let me talk of this with SukkoPera, I'm sure we can arrange something.

  8. #8
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    Thank you, please let him know that I'm using the "legacy" branch, I'm not using the master branch, I've had issues with it. The legacy branch I'm able to reset with my 3 button, 6 button, and 6 button wireless 8bitdo controllers. And thank you for your in-depth descriptions toy questions, been reading them over and over.

    Edit: pin 26 of the Z80 is ZRES, would soldering to that pin, from either the reset in/out locations the Nano uses, do the trick when trying to reset from the controller?
    Last edited by infidelity; 01-12-2020 at 01:55 PM.

  9. #9
    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    Quote Originally Posted by infidelity View Post
    Edit: pin 26 of the Z80 is ZRES, would soldering to that pin, from either the reset in/out locations the Nano uses, do the trick when trying to reset from the controller?
    No. At the moment the problem is that the micro is not sending any reset sigal. Because It is not getting the right buttons combo.
    The fix will allow to use a different buttons combo in the SMS mode by using only the B and C buttons.

  10. #10
    Hedgehog-in-Training Hedgehog-in-Training SukkoPera's Avatar
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    I didn't implement IGR when in SMS mode because I couldn't come up with a button combo that is unlikely to be pressed during normal gameplay. Remember that presses of the Start and A buttons cannot be detected in SMS mode, since MD++ only passively snoops the controller bus and SMS games will never read those buttons.

    Now majinga gave me the idea of holding a combo long enough, maybe B+C+Down for 5 seconds. This might work, I'll look if I can implement it, and I will make it optional for those who don't want to undergo the risk of accidentally resetting their console.

    But I will do this on the master branch, the legacy one is not supported anymore. I have never had any issue reports with it, so you either did not install it correctly (the wiring is different) or if there are actual issues you should have reported them so that I could fix them.

    EDIT: I have looked a bit into it and it doesn't look as easy as I initially thought. Also I have no way of testing this, since I don't have any cart converter nor an Everdrive. Mmmmh...
    Last edited by SukkoPera; 01-12-2020 at 06:32 PM.

  11. #11
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    Thank you for looking/attempting. I'll try one more time with the master branch, I'll redo my wire setup according to the master branch.

    Curious. TH on the front control ports are off when in SMS mode, but I was looking at the schematic of the motherboard and noticed the EXT port doesnt have anything showing TH is disabled (I think). I didnt know if there was some sort of genesis modification separate from the Arduino Nano, that k can do to have the start button activate the ZRES on the Z80?

  12. #12
    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    Quote Originally Posted by infidelity View Post
    ... there was some sort of genesis modification separate from the Arduino Nano, that k can do to have the start button activate the ZRES on the Z80?
    I don't think there is a simple solution for this. You neeed to feed the clock signal to the pad to get the start button. But only in the SMS mode. In the normal MD mode you must allow the clock from the MD to pass through. Or feed an exact replica, same timing.
    Last edited by majinga; 01-13-2020 at 02:48 PM.

  13. #13
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    There's gotta be a way if Sukko was able to get the start button enabled in sms++? I'm going to keep reading schematics, if my idea of getting start/a functional outside of md++ then so be it, I need to trigger that reset from the z80.

  14. #14
    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert majinga's Avatar
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    From what i read, he feed the clock signal to the pad. For the mod on the SMS you have to cut the traces from the db9 connector. The micro take care to send back to the SMS the signals of the buttons.
    He rely in the face that in the SMS the pin used to feed the clock to the pads was never used, it Is always high.

  15. #15
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker infidelity's Avatar
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    Yeah I saw that MSII motherboard of what he did with the trace cutting. I'm trying to figure out if its the IC that is disabling the TH when in SMS mode? I looked at the IC pinout and see that it's both input/output.

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