Go Mobile Gaming with RetroPie!

Go mobile gaming with RetroPie. RetroPie bundles a ton of emulators for lots of different gaming platforms and is amazing! With all this great software, I took the plunge and built three handheld gaming devices using the Raspberry Pi Zero W. For this project I picked three popular project kits:

At the most fundamental level, all three of these kits use the Raspberry Pi Zero W so they all run the same code on the same hardware. Because of this, I will evaluate them based on features they bring to bear, build difficulty, quality, and overall impression.

A Word About Tools

As a quick aside, let’s talk about the tools necessary to build a hand held gaming system. The experts will tell you there is a good tool and a tool that makes things possible. I will tell you that the good tools are necessary for consistent results. Some of them are rather expensive. That said, I wanted to list the tools that will help you go mobile gaming with RetroPie.

There are a couple of things I didn’t want to mention specifics for but that you should also acquire. First is a good multimeter. Browse Amazon to find one. You will need one of these to test your solder joints, particularly when building the Null 2 and Picicle. When you get weird results, chances are extremely good this stems from a pad or two not being completely connected. The second thing you should acquire first is stranded wire in 26, 28 and 30 gauges, preferably with silicon insulation. Adafruit has this stuff all day long. There are times when you need to tie things together, like USB ports and speakers. Using the wrong wire can make it impossible to assemble once you are finished. A silicon insulating jacket is harder to melt and is much more pliable in tight spaces.

Hakko FX-951 ESD Safe Solder Station

Permanently cluttering a portion of my desk now is a Hakko FX-951 solder station. It is far and away better than the $15 soldering irons I used for the first 45 years of my life, and I cannot express how much of an improvement this represents overall. I selected the Hakko T15-JS02 tip which resembles a pen refill, but which provides a curved, fine point. It is perfect for smaller solder joints. The Hakko unit also does a great job of heating up and cooling down extremely quickly, and holds a perfect steady temperature. I highly recommend this or a similar Hakko solution for this project.

Kester Solder 63/37 .015 Diameter

The solder you select should have a melting temperature that is safe for the work you are doing. For this project, it should also be thin enough to not drown the tiny parts you’ll be working with. When you’re soldering a capacitor or resistor that is no more than a couple mm long, you’ll need to be working with this kind of material. Also, LEAD. The 63/37 represents the percentage of lead in the product. 63% tin and 37% lead. Ventilation is key here. A small fan and a window? They also make fans to suck the fumes through a filter. Do not breath lead fumes.

Solder Paste / Flux is critical!

I don’t necessarily have a recommendation for a particular product here, but search Amazon and find a good solder paste/flux. You need this to help keep things clean and to draw molten solder to contact points. You will be super happy with the results. Also pick up some of those individually wrapped alcohol wipes like nurses use. They are perfect for cleaning up excess solder paste so things turn out beautiful.

Prusa Mk3S 3D Printer

Okay, this isn’t entirely necessary except that the Pi Grrl Zero and Null 2 have 3D printed cases. If you do not have a 3D printer yet, this is the best one in my opinion. Also, where have you been? Any modern maker should have this and a free hobby license of Fusion 360 at the ready.

M3 and M2.5 Screws and Nuts

I highly recommend going to Amazon and ordering a couple of multipack cases of M3 and M2.5 socket head screws. You won’t need them for everything in this list, but they come in very handy in general when making things these days. I used a few short ones to hold the internals in the Pi Grrl as an example. They aren’t expensive and they are not readily available in stores that I have found.

Mobile Gaming with RetroPie and Pi Grrl Zero

Up first is the Adafruit Pi Grrl Zero. I love Adafruit! They have so many cool ideas, projects and information. Their projects are great learning tools, and the Pi Grrl Zero is no different. Like the rest of my three projects, the heart of this handheld is the Raspberry Pi Zero W. Note that using the wireless version of the Pi Zero will require you to manually install the software from a base RetroPie image. Even with this caveat, the instructions provided are very good, and the entire process is outlined perfectly.

Pi Grrl Zero W

There are many good things about this project and I think they boil down to it being a relatively low stress way to learn more about handheld gaming. You will have to solder quite a bit, but all the connections you make are pretty easily accomplished. The practice you get doing this project will prove invaluable on the others. While the Adafruit site warns this is not a beginner project, it is by far the easiest to build out of the three projects I list here.

Pros:

  • Great instructions
  • High quality parts
  • FUN to build!
  • No intensely small or delicate parts
  • Includes a full USB 2.0 female port for connecting keyboards, etc.

Cons:

  • Small Screen
  • Loud buttons
  • No sound
  • Manual Shutdown Procedure
  • Have to dismantle to remove the SD card (but shouldn’t be necessary, really)

The Pi Grrl Zero is a great platform to start from. There are plenty of remix projects where people have increased the size of the screen and added sound. If you’re into it, I would love to hear how well you are able to use it to go retro-gaming using the Raspberry Pi Zero and RetroPie.

Mobile Gaming with RetroPie and Picicle

If you haven’t heard of the Picicle Kit, you’re in for a treat! There are a couple of important differences between this kit and the Pi GRRL Zero. The first is that it ships with Acrylic parts for the case and buttons. You’ll have to glue it together, and they recommend UV activated super glue for this purpose. Use it sparingly.

Picicle. Yes, I built two.

Pros:

  • Sound! It uses a single speaker, but it works.
  • Bigger Screen
  • Buttons are quiet
  • Power off initiates automated shutdown
  • It’s Pretty! Custom PCB for everything.
  • USB and SD Card accessible fully assembled.

Cons:

  • Difficult to Build
  • Testing solder joints requires two heads and 4 hands.
  • Mini USB… Only PS3/4 controllers still use that, right?
  • Acrylic screws. I’m sure there is a better way.

I really enjoyed building the Picicle kit because I learned a great deal. If you have never surface soldered a Raspberry Pi to a board you might want to figure out a good way to practice first. I suggest using a very small amount of solder and definitely use flux. In the end, this is a great way to go mobile gaming with RetroPie.

Picicle Build Advice

When you assemble the Pi to the Picicle board, you will have to work hard to make sure the header pins are properly aligned. I used two M3 screws with nuts to secure it to the board after I had used alignment pins on the GPIO header. I made small adjustments by holding it up to the light. There are a couple of pinholes that will help make sure you have things perfectly centered. Then as an added measure, I used capton tape to help make sure the header side of the board was firm against the PCB. This will help ensure the least amount of solder is used with the least chance of it bridging to other pins.

Use an incredibly small amount of solder and do not fill up the cavity created by the GPIO header holes. You should actually see the solder bubble sink down into the cavity. Also, be sure to check every single connection that is listed to test. There should be 0 ohms resistance for every single one. The results if you do not do this, even for the nearly impossible screen pads, is regrettably wild.

If you leave a divot in each of the GPIO header holes, they serve to hold the tip of your multi-meter during testing. That’s especially handy when you have to test the other end on the other side of the board. It also hopefully keeps you from creating bridges between the PI and the board, which would be difficult to fix. In my opinion, this is far from the most difficult part of this kit assembly.

What exactly was so difficult with the Picicle?

It was simply tedious. Be patient while soldering each individual piece. The surface mount resistors and capacitors are tiny. They are not difficult to get right, they are just very small and easy to lose. The big trouble spots for me wound up being the TP4056 charging IC, and the mini USB connector. I managed to fix both problems by using the solder wick and pulling excess solder from them both. I later went back in and prettied them up. The charging IC of course caused it to not want to charge the battery. The USB port resulted in a high pitched squeal that would never end once I had powered the unit off. When it was on, it worked fine.

One way you might combat this in your own build is to have younger eyes or use a microscope during assembly. Something to magnify the work in a substantial enough way to allow you to more accurately apply solder. I believe in my own build my problem was not believing I was getting enough solder and then overdoing it. The USB port in particular, I never saw where the short occurred. I think it might have bridged to the case metal from one of the pins, but the space is so small, I never saw where it happened.

Mobile Gaming with RetroPie and Null 2

The Null 2 kit is probably my favorite one over all. I only have one mild gripe and that is the shutdown requires a key combination, then a power off. I prefer the way the Picicle implemented a shutdown of the Linux system simply as part of what happens when you turn the switch off. There is a single sheet operator’s manual online which is a nice touch. Not everything is obvious with this one.

That said, the Null 2 provides a custom PCB like the Picicle, but separates audio and charging to a custom made set of separate boards, so assembly is greatly simplified. The quality of the audio is far superior as well, not just for being in stereo, but overall. There is only one surface mount resistor, and just be aware, it is loose in the packaging and easy to lose.

Null 2

Pros:

  • Stereo Sound
  • Relatively Easy Build
  • Headphone Jack
  • Quiet buttons
  • Test pads right beside major solder points

Cons:

  • Advised to charge only while turned off
  • A bit difficult to assemble the case itself.

The case for the Null 2 is up to the builder. There are a couple provided via Thingiverse. I opted for the version with the deeper back to accommodate the battery. There are remixes out there, and there’s nothing stopping you from drawing your own up and going a completely different route. You are also provided with plans for an acrylic version as well.

Conclusions and Postulations

Overall Winner: Null 2

I already let the cat out of the bag on my favorite, and that’s the Null 2. It was an easy build, there are test pads galore, making verification of solder joints a snap. The SD card is exposed for easy exchange after the build. The sound is excellent.

Build Challenge Winner: Picicle

From a satisfaction standpoint, I was looking to be challenged, and for that the reward goes to the Picicle. It was my first foray into surface mount components and it delivered frustration in spades. I used support chat on Tindie a couple times and received adequate support leading to success.

Learning Winner: Pi GRRL Zero

I started with the Pi GRRL Zero, and I am glad I did. It is a functional unit, it is easy to get things right with it, and it is fun. I keep a couple of these with me at family get togethers and hand them to unruly children. If you’re looking to just try things out, I highly recommend this unit.

Final Thoughts on RetroPie Gaming

When you get ready to go mobile gaming with RetroPie, I hope you have as much fun as I’ve had. These kits are fun to build and entertaining to have. I genuinely hope you find the information I’ve provided helpful and look forward to hearing from you if you decide to build one of these kits yourself.