Dummies Guide to SNAC?

[mmmonkey]

Can anyone help me with SNAC? I’m in the process of building some of the controller boards, after having just built the ‘USB’ version of the main board.

I have an IO Board 5.5. I understand I’ll need to mod this for use with the Sega SNAC adapter board (I’ve got some pictures saved of what I believe is necessary to do)

I’ve got a PCE board complete, but before I plug it all in, I think I need to leave the jumper link on the main SNAC board open?

What is the purpose of x1? Some photos of assembled SNAC main boards I’ve seen haven’t soldered the JST connector in.

Thanks
Pete

[funky327]

I am also in the same boat, building an HDMI based board for myself. There is no documentation on any of the settings (jumpers/JST connector usage) on the SNAC board in the repo or elsewhere that I can find.

Thanks!
Eli

[dshadoff]

I know I'm not answering your main question, but...

I'm not sure what PCE peripherals you're planning to plug in to SNAC, but be forewarned that the current open-collector designs don't work well with anything beyond a simple 2-button pad (or FTDI cable if you're using Chris Covell's PCEmon). I'm looking into ways to improve this, and will update the TGFX-16 core forum if/when there is any news.

[dshadoff]

I think you need to get those answers from "blue", the designer of the board. (re: jumper and JST connector).
I'm pretty sure that the jumper is related to using one additional line on the SNAC connector - which needs a corresponding modification to the I/O board (up to version 6.0).

I have an IO board version 6.0 and I leave the jumper and connector open/unconnected.

[funky327]

Thanks for the info, I will try and reach out to blue212 for more information.

[belgarcat]

Please post all the findings you get from blue212
I'm about to start assembling the SNAC board, and I'm also hesitant about the jumper in this board. In my case, I have a DigitalIO v1.2 which has an jumper selector for NES/SNES and Genesis connections. In this case, don't know if I should connect or not the jumper in the SNAC board.

[crispycritter911]

This is the modification I did to my older I/O board. I've since upgraded to the digital I/O. I've made both a USB and HDMI versions of SNAC from a UK seller. My understanding that if you have a jumper for I/O pin or the modification to your board, you can leave the jumper plugged in on the SNAC board. If you do not have this option on you IO board, leave the jumper out.

[guzzard]

This is the modification I did to my older I/O board. I've since upgraded to the digital I/O. I've made both a USB and HDMI versions of SNAC from a UK seller. My understanding that if you have a jumper for I/O pin or the modification to your board, you can leave the jumper plugged in on the SNAC board. If you do not have this option on you IO board, leave the jumper out.

Do you remember which version I/O you had? I want to do this modification on my 5.6XL I/O board but it seems impossible to find any official guide or information on this..

[JayBee]

I just did the mod for the 5.6XL, using this image:

w0vAb8U.jpeg (2.69 MiB) Viewed 10676 times

There are basically 2 traces to cut, and one wire and a 100 ohms resistor to solder. My Snes and PC engine controllers work perfectly with it, however I can't get my Sega Genesis Justifier gun to work, so I'm not 100% sure it works.

[guzzard]

I just did the mod for the 5.6XL, using this image:
There are basically 2 traces to cut, and one wire and a 100 ohms resistor to solder.
My Snes and PC engine controllers work perfectly with it, however I can't get my Sega Genesis Justifier gun to work, so I'm not 100% sure it works.

Thanks for the picture and info! I'll give that a try. I don't have a gun for Sega, but I could at least verify that controllers work (NES, SNES, Sega), and NES Zapper.

[guzzard]

Ok modded the I/O board.

- NES Zapper work fine
- SNES original controller works fine
- Mega Drive/Genesis retro-bit official 6 button Sega controller acts super wierd. In 240p test-suit I can test all buttons but when pressing start it registers almost all buttons except A and B. I tried playing Flashback, and in the menu buttons work, but in-game only start button registers. I also tried playing Psycho Pinball and in the menu a couple of button presses are registered even though nothing is pressed. In level select d-pad does not work. In-game d-pad works etc.. very strange issues.

I think these issues are related to the controller, perhaps some timing issue? Unfortunately I don't have any other Sega controller to test with at the moment..

Anyone recognize these issues? Perhaps retro-bit controller model is not compatible with MiSTer through SNAC?

[legacypixels]

Ok modded the I/O board.

- NES Zapper work fine
- SNES original controller works fine
- Mega Drive/Genesis retro-bit official 6 button Sega controller acts super wierd. In 240p test-suit I can test all buttons but when pressing start it registers almost all buttons except A and B. I tried playing Flashback, and in the menu buttons work, but in-game only start button registers. I also tried playing Psycho Pinball and in the menu a couple of button presses are registered even though nothing is pressed. In level select d-pad does not work. In-game d-pad works etc.. very strange issues.

I think these issues are related to the controller, perhaps some timing issue? Unfortunately I don't have any other Sega controller to test with at the moment..

Anyone recognize these issues? Perhaps retro-bit controller model is not compatible with MiSTer through SNAC?

There are known issues with the Retrobit 6 button and SNAC. The Retrobit is less tolerant of too tight timing loops with some Genesis ROMs

[guzzard]

There are known issues with the Retrobit 6 button and SNAC. The Retrobit is less tolerant of too tight timing loops with some Genesis ROMs

Thanks for the info! Is this know issue documented somewhere or is it something I would have found out by googling and searching through forums?

Would be really great to collect all these pieces of info regarding how to modify the older versions of the I/O board, as well as information regarding controller compatibility etc, perhaps wiki page in SNAC github repo? I will reach out to blue212 and see if that's possible. I can help with documentation as well.

[legacypixels]

There was quite a discussion over on the Classic Gaming MiSTer forum, Someone was having issues with Earthwom Jim with SNAC and a Retrobit 6 buttton. The problematic ROMs read the button state too soon after the SEL line gets toggled. The uC in the newer controllers doesn't respond quickly enough. Various and sundry analog voodoo (resistance and capacitance from extension cables and controller cords) can contribute to the issue as well.

[JayBee]

Not sure if that helps, but the mod I linked earlier is working perfectly now, after testing it extensively.
But in order to get my Sega Justifier to work correctly, I had to put the jumper in the correct position on the SNAC board (bridged position).

[venice]

I just did the mod for the 5.6XL, using this image:
There are basically 2 traces to cut, and one wire and a 100 ohms resistor to solder.
My Snes and PC engine controllers work perfectly with it, however I can't get my Sega Genesis Justifier gun to work, so I'm not 100% sure it works.

Thanks for the link.

I have a 5.6 Board as well and like to mod it for Sega Controller but I think 2 cuts are not enough.
If you cut only the two lines at the bottom side there is still an top side connection between the modded SNAC Pin (The Yellow Dot at the drawing) and R42/R43/R44.

As all Data Pins on ioboard 5.6..6.1 have an 10K/100Ohm Resistor combination i added the following in addition to the linked mod:

• Another 10K Resistor connected to C7/3.3v and the 100hm Resistor

• A third cut on top to remove the connection between the modded SNAC Pin and R42/R43/R44

• Another connection from 3.3V to R42 (Red Line)

Does this makes sense or is this too much?
Maybe I am completly wrong?

ioboard_5.6_sega_mod.png (262.52 KiB) Viewed 13480 times

[wesclemens]

Does this makes sense or is this too much?
Maybe I am completly wrong?

Did anyone end up trying this? Was it the correct solutions?

[sk8er000]

Are the schematics to mod the v 5.5 available? I'm not finding them unfortunately.

Thank you in advance

[sk8er000]

I may found the answer, and added pull up resistors too:
viewtopic.php?f=32&t=3433&p=35292#p35292

[peke]

Hi, I´m in the same boat (IO board 5.6-xl), I want to use atari 5200 controllers and atari paddles. did someone manage to make it work?

[Breaking Hard]

Hi all, I do same mod on my v5.5 just add liitle bit accuracy.