My first cab - RetroPie-powered custom Donkey Kong bartop

[vinegar]

for my first real cab project, i scratch-built my brother a custom Donkey Kong bartop for Christmas! he was incredibly excited, and i thought others might like to see it.  there's quite a bit of arcade sacrilege going on here, but it's a bartop DK so history is already out the window    hope you can forgive me.

it's mostly 1/2" birch plywood with 3/4" MDF for the control panel, running on a Pi 3 with RetroPie and the brand-spanking-new LiFePO4wered/Pi3 UPS functioning as a safe shutdown system.  no need to teach my brother any shutdown procedure, he just flicks the mains switch and the UPS takes care of it with the long-life and safety of a LiFePO battery letting me keep the pi's SD card writable without worry of corruption.  I was incredibly fortunate xorbit got this UPS ready for shipping in time and it works great.  i sound like i'm shilling for him, but it really was the linchpin in this whole system for me.

one somewhat unique bit here is that there are no traditional speakers in the cab, and thus no speaker holes.  instead, i'm using transducers which transfer vibration to solid objects and make the whole surface a speaker cone.  gives me a nice seamless look.  i was a little worried they wouldn't work with the monitor mount and everything else stiffening the side panels i'd mounted the transducers to, but it worked out great. there's no muffling and they can get REALLY loud.

buttons and sticks are from focusattack.com
side panel art and polycarb laminated CP art printed by gameongrafix.com
marquee and system button art printed by posterprintshop.com
t-molding from, of course, t-molding.com

full gallery is here: http://imgur.com/gallery/ctqVE

thanks for checking it out!

[DaredevilDave]

Cool! I checked out your page.

This is interesting (copied for those who may not go to your other page):

you'd note there's no holes for speakers in any of these pictures, and that's because i'm using transducers which you can see here mounted to the side panels. they transfer vibration to solid objects, turning the side panels themselves into speakers! even with the structural supports inside the cabinet, they sound great and can get LOUD even with the little 3x3 amp you can see poking out on the bottom left.

Do you get a good frequency response/range this way? If you play music through it does it sound good?

I've thought about using a Pie for my vertical cocktail. You mentioned latency - is it noticeable when you play a game or did you test for this? The Pies sound cool but I'm afraid I'd wish I hadn't used one at some point.

Your build looks excellent, I like the work you did. 

[vinegar]

thanks! this cab is mostly classic mame, so it's really only ever playing chiptunes originally blasted from not-the-best speakers.  it sounds wonderful   i could have maybe used a dedicated low-frequency transducer to give games like asteroids more foreboding bass, but i'd have to incorporate a low-pass filter on the amp and it really wasn't worth the effort imho.

as for the latency - i didn't formally time it, but it was certainly noticeable on more intense games.  note that i'm only referring to button latency from specific interfaces; directly wiring buttons to the pi's GPIO pins vs. a separate, dedicated keyboard encoder (in my case, a pro-micro arduino programmed using a low level pin interrupt library, similar enough to the cheapy keyboard encoders you'll find on ebay).  though you can access and attach hardware interrupts on the pi's GPIO pins, they have a lot of competition with the rest of the system.  even with USB HID overhead, the arduino was faster and more consistent at reading and sending inputs to the pi.  the reason i used an arduino was that it's cheap, and i wanted a dedicated game exit button.  the retroarch emulator shell that retropie runs uses combo hotkeys for functions like game exit, and while i provided a shift button for other things like pause and save/load state, i wanted something as important as exiting a game to be blatantly obvious.  so my arduino code sends shift + exit game hotkey when you press that button.

the pi 3 itself is plenty beefy for loads of crazy games, even notoriously sprite-heavy, newer japanese shmups like dragon blaze given the right emulator core.  it took some experimentation to find which of the cores that come stock with retropie worked best with each rom and rom version.  it's not beefy enough to run a PSX emulator for sure, though dolphin (GC/Wii emulator) has gone through some crazy optimization in the last year or so and may be fine.

[vinegar]

oh, but vertical.  that's a tiny bit of an issue with the pi.  for everything to be rotated everywhere, you really have to set display_rotate in the bootloader, and something i couldn't pin down gets funky in the GPU firmware (all up to date) giving you some (very) minor screen tearing in motion.  when i presented it at christmas, nobody noticed until i pointed it out, and they all started saying i'm a little crazy 

[DaredevilDave]

oh, but vertical.  that's a tiny bit of an issue with the pi.  for everything to be rotated everywhere, you really have to set display_rotate in the bootloader, and something i couldn't pin down gets funky in the GPU firmware (all up to date) giving you some (very) minor screen tearing in motion.  when i presented it at christmas, nobody noticed until i pointed it out, and they all started saying i'm a little crazy 

In Windows I've decided to rotate my entire OS rather than just MAME. I'm assuming by what you said that this isn't possible on a Pie? That's a killer if so.

I have a custom 3D front end that I made. I can compile it to Linux if that's what the Pie uses. Hmm actually I'm guessing "no" on 3D/Pie now that I think about it. I can use Mala.

Ya, after spending so much time getting MAME and my front end the way I like it, I think I'd better stick to a PC. Wish I could get windows on my old Mac Mini but I never got it to work (except a VM but that's deadly slow for controllers/latency).

I like the idea of using a UPS for shutdown. Not sure I'll worry about it since this cab is for me - I think. But good info. I wonder if you could just program a "button" on the top of the cabinet to activate normal Windows shutdown. Maybe using something like "joy to key" to make it simple.

Thanks for the info!

[vinegar]

In Windows I've decided to rotate my entire OS rather than just MAME. I'm assuming by what you said that this isn't possible on a Pie? That's a killer if so.

no, totally possible on the pi, you just really need to do it in the bootloader's configuration so EVERYTHING is rotated rather than trying to do it in software for your shell, mame, whatever etc. individually (which is an actual thing you can try to do if you're crazy).  problem is that minor bit of screen tearing when the GPU firmware is running in a rotated mode like it will be when you do it in the bootloader.

I have a custom 3D front end that I made. I can compile it to Linux if that's what the Pie uses. Hmm actually I'm guessing "no" on 3D/Pie now that I think about it. I can use Mala.

there's a build of windows 10 that'll run on the pi's arm proc, but i wouldn't use it and expect performance.

I like the idea of using a UPS for shutdown. Not sure I'll worry about it since this cab is for me - I think. But good info. I wonder if you could just program a "button" on the top of the cabinet to activate normal Windows shutdown. Maybe using something like "joy to key" to make it simple.

windows has this built-in as a function available to the regular power button wired to any motherboard i've used in recent memory.  in the default power save configuration, pressing power while the system is on sends it to sleep, but that's configurable to immediately shut down instead.  then you've got one power button to rule them all, no fuss.

[DaredevilDave]

Ah yes, forgot about the power button shutdown thing. No need to reinvent the wheel!

I rarely shut down my standup, it just sleeps. I stream movies from it too so it's multi-purpose. AND I play racing games (Daytona, NASCAR...) through it on my big screen with 2 extension cables (HDMI and USB). It's a good PC so may as well use it.

I actually use it to test the cocktail cab too for now. One PC for an entire arcade! 

I get tearing on my standup. Figured it was my video card. LCD screen. I'm using a CRT in the cocktail cab. I've messed with vsync and some other stuff and haven't solved it. Actually I think my own game (Daredevil Dave) tears, so ya probably the card.

[yotsuya]

Dave,  you eat Pie. You program the Pi.

[jdbailey1206]

Dave,  you eat Pie. You program the Pi.

[stigzler]

Tidy little machine - nicely put together. Liking the transducer speakers. Disliking the Christmas tree.

[DaredevilDave]

Dave,  you eat Pie. You program the Pi.

Well it used to say Pie on their website! I swear it did!

I KNEW it couldn't be Pie, but ...aah crap haha. I'd rather have pie right now. Hungry.