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25 January 2017

Building the PiCart RetroPie housing

I saw Zach's writeup on his Pi Cart RetroPie build, and just had to try it. Definitely follow his instructions--they're really easy, and he covers a lot of the potential pitfalls. This post doesn't cover anything new, I just figured I'd document my foray into what it was like to put one together with stuff I had on hand. The second hardest part of this project was getting my hands on the Pi Zero, since Adafruit has them in and out of stock at random. The hardest part was winding all the cables inside the cart to make everything fit.

Here's the stuff I collected for this project:

1 16GB Sandisk MicroSD card (Class 10; speed is important)
1 Micro USB to USB-A adapter (the super small kind)
1 male to female Micro USB adapter
1 4-port USB hub (Link is to the one Zach used)
1 Nintendo cartridge of your choice
1 USB Wi-Fi adapter (optional)
1 USB Drive for ROM transfer

1 3.8mm Security bit
1 Box cutter with new blade
Hot glue gun
Lots of patience

As usual, click on the photos to make 'em bigger if you want to.

Zach's instructions use an Amazon Basics 4-port USB hub, which is only about $6. But I have USB hubs lying around, so to keep costs down, I used one that had two ports on one side and two ports on the opposite side. This way I could plug the WiFi dongle in at the back and add a bluetooth dongle later if I wanted. Power usage is a concern, though, so I probably won't. All you really need is two accessible ports for two controllers, and you can always unplug a controller to update ROMs via USB drive.

Before you start, maybe test the Pi to make sure it works. I've never had a problem with any Raspberry Pi boards, but you never know. Download the RetroPie image (you want the Raspberry Pi 0/1 version for the Pi Zero) and follow the instructions on the RetroPie page for installation. Plug the card in and boot the Pi, ideally with a controller attached. If everything works, assemble your PiCart!

I got everything together and opened up the cart using the security bit. There are a few free alternatives online for opening the cart, but trust me, buying the security bit or screwdriver is worth it.

There isn't a whole lot of room inside an NES cart, even though the thing is mostly filled with air. I pulled out the original game board and marveled at how big it was compared to the Pi Zero.


The Pi Zero needs to be held to be believed. It's about the size of half a graham cracker square.

Or about a fifth of a dollar bill.

I laid down a towel so the tiny parts wouldn't bounce away too easily, then got all the pieces out to assemble. The cables were all stiff and new (especially the HDMI adapter), so I figured I was in for a challenge.

The new guts.

The USB adapter is tiny...

...but it works.

I started by following Zach's instructions, and kept modifying as I went, since I was using a different hub and cables. The HDMI adapter connected to the Pi, the USB adapter plugged the hub into the Pi, and the male-to-female Micro USB adapter felt way too short...but would probably work.

So far, so good.

I was originally planning to keep the shell on the USB hub, since it seemed to fit as it was, but I decided to open it up to create a little extra air flow. The Pi Zero runs pretty cool, and it won't be handling any demanding games, but it does warm up while you play. This RetroPie will be set up to play the classics, because nostalgia. Those were the best games anyway. Don't judge me.

The USB hub isn't powered, and the Pi Zero doesn't put out a whole lot of extra power, so I scrapped the plan to add a bluetooth dongle. I wanted to keep the Wi-Fi dongle, though, for updates and metadata scraping.

I scored the divider on both halves of the cart, then pushed it to snap it off. It actually broke pretty cleanly. Then I sanded it smooth, mostly to rough up the plastic to give the hot glue a bit more purchase.

The Pi goes right about there.

Then I spent a stupid amount of time just moving stuff around and bending wires to find the best fit. There's really no preparing for this, you just have to figure it out through trial and error. The HDMI cable is NOT very flexible, so that took precedence. I was able to wedge it against the middle screw post to keep it bent.

I eventually got down to figuring out what to layer and how, making sure the USB cable threaded underneath the HDMI adapter cable. The HDMI had to wind over the corner of the USB hub's PCB, so I figured the natural gap underneath would be enough room for the Micro USB adapter cable.

I hot-glued the HDMI, Micro USB adapter, and USB hub in place at the front of the cart. They had to be there no matter what, so I figured with them glued down I'd have a better grasp on how the cables had to run. I built up a small layer of hot glue under the USB hub to raise it up a bit before gluing it in place. The Wi-Fi dongle fit nicely against one of the other mounting posts inside the cart.

That upper left USB port stays unused.

I ended up shaving flat the HDMI adapter and peeling the excess plastic off the USB plug on the USB hub. They were both just too thick, and with everything contained within the NES cart, they wouldn't be exposed to the elements or physical abuse.

I might have shaved a bit too much off the HDMI cable and damaged the shielding; time will tell. I also had to break off the power input on the USB hub to make room for the HDMI cable, and in doing so, I took out what looks like a fuse. The hub still works, though, so I'm going to optimistically assume it was a fuse for the now-missing power port. 

The Belkin USB Hub I used had a ridiculously long, metal USB plug under the plastic. It's that entire 2" metal thing in the second photo below. Really, who asked for that?

The winding process.

There! A super-tight fit.

Once the cables were mapped out and mostly in place, I adjusted the Pi to put as little stress on the plugs as possible and marked the mounting holes by digging the end of a push pin into the plastic of the cart. I placed hot glue blobs over the marks, let them dry, then plugged in all the cables, positioned the Pi, and (holding everything so it didn't move) pushed more hot glue through the mounting holes to fix it in place. With just the four points glued down, the Pi would be easier to separate from the cart if needed, and it would have some air flow all around it while it worked.

I wasn't too concerned with only two exposed USB ports, since all functions can be done with two--ROM load and controller or keyboard, or a two-player game. The Wi-Fi dongle was inside, so technically didn't take up any space. It's like a secret bonus functionality, and it's less likely to get lost in there. I put a dot of hot glue behind it so it wouldn't get jarred loose.

Having only two USB ports left a big ol' gap in the front of the cart, though. I wanted this to be a self-contained kit with a dedicated USB drive for transferring ROMs, so I figured I'd hot glue the cap for the USB drive in place as a kind of dock. That way, the USB drive can't get misplaced quite as easily. I left the string attached, clipped off the metal bit, and the string can be tucked inside.

Obligatory note on ROMs: Downloading them is shady at best. They're out there, but play fair. What's nice about the RetroPie is having all of my favorite games in one place, on a system that can plug into my new TV without a UHF adapter. If it's so handy, why am I keeping all my original consoles, carts, and discs? Because nostalgia. Don't judge me. If there's a fire, I'm totally jumping out the window clutching my SNES. The cat can fend for itself.

Built-in USB, storage.

The only thing left was to reassemble the cartridge. I meant to buy a few phillips screws to replace the Nintendo security screws, but never got around to it.

Not too shabby!

The Pi Zero performs really well for anything up through the Sega Genesis/Megadrive era. With two controllers plugged in, the hub works with no power issues. I was able to scrape a bunch of cover art via Wi-Fi with no hiccups.

Kudos to Zach for coming up with an easy-to-follow idea. The Pi Cart is a head-turner and a fun (and portable) way to play with your RetroPie build. I did this one as a Christmas present for a friend of mine, and he was really happy to get it. It sits nicely in his current library of NES cartridges as a sort of stealth option for when he gets tired of blowing on the real carts to get them to play.

It's nostalgia. Don't judge him.