GPi Case 2 - Compute Module 4

The GPi Case 2 with Raspberry Pi's Compute Module 4 is the ultimate portable gaming device. The case offers amazing functionality, and when combined with a CM4 and 64-bit Recalbox, there is little that can challenge it for a portable retro gaming experience.

For this project, I went with a Compute Module 4, with 32Gb eMMC storage, and 4Gb RAM. I also went with no wireless, as this is my portable gaming device, and I don't require any online functionality for it. If you've read my NesPi-4 guide, you will know that I prefer RetroPie as my emulationstation frontend, but for this project I went with Recalbox instead. The biggest issue I've had with Recalbox in my Nespi-4 case, was that some updates would break the operating system sligthly. The web UI where you upload your games would stop working, and the shutdown option would disappear from the start menu. But as I don't really run this device online, the WebUI isn't as much of an issue, and the safe shutdown script for the GPi Case 2 means that the missing option isn't really an issue either. Although, I haven't really encountered the same glitches when updating Recalbox on this device. Recalbox also has a few features that let it pair extremely well to the GPi Case 2. It is 64-bit, which helps a lot with performance - I haven't overclocked it, as there is no cooling inside the case, but I still get great performance when emulating PSX, and it runs Mr. Driller and Volgar the Viking well on the Dreamcast - I haven't tried any games more taxing than those though, as it a battery powered device, and working it too hard is going to drain it faster. Recalbox is quite opinionated as far as emulationstation station frontends go, and to my knowledge, there is no way to add new emulators to it, although it does come prepacked with a more than reasonable collection of emulators, as well as lots of homebrew game ROMs, which is a very nice touch!

Setting Up

First you will need to flash Recalbox to the eMMC storage on the compute module 4. Either use the image provided in the Raspberry Pi Imager (Recalbox - Raspberry Pi 4 / 400 (64 bits)), or download the image from Recalbox and install using your software of choice. To install directly onto the CM4's flash storage, we will need a piece of software that overrides the boot method on the CM4, and registers the device instead, as a storage device.

First, we will need to check that libusb-1.0-0-dev is installed on your computer that you will be using to flash the CM4. Check using:

apt list --installed | grep libusb

libusb-1.0-0-dev should be in the list. If it's not, then install it using:

sudo apt install libusb-1.0-0-dev

Next, we need to clone the Raspberry Pi USB Boot repository.

git clone --depth=1 https://github.com/raspberrypi/usbboot

Next we need to build the software:

cd usbboot
make

Now we can run the software:

sudo ./rpiboot

Now, plug the GPiCase 2, with compute module 4 board installed, into your PC while the usbboot software is still running. You need to use the micro USB socket on the back of the case, under the cartridge style cover. Now power on the GPi Case 2, and the computer will now recognise the CM4 as a storage device. You can install the image just as you would an SD card.

BIOS's

You can get a full set of the RetroPie BIOS's at this repo (if you need help getting BIOS's from it, have a look at my NesPi-4 guide for instructions). I haven't checked every single one, but they should cover most of what you'll need for Recalbox. Check where to load each BIOS in the RecalBox Documentation. Use the installation instructions described in the next section about ROMs to install BIOS's onto the device.

Adding ROMs

I'm not going to tell you where to get copies of ROMs you already own physical copies of, but if you need help with it, take a look at the Getting Games section in the Nespi-4 guide. To load the ROMs to CM4, you will need to run the usbboot software again, as with the installation. Games will need to be loaded onto the Share partition, check out the RecalBox docs for the correct location and formats of ROMs for specific emulators.

Tweaks and Polish

Theme

The Next Pixel theme is great for the small LCD screen on the GPiCase. It looks great and the font sizes are large enough to be readable. To install just clone the repo to your computer, then drop the folder into the recalbox/themes folder on the CM4 device.

git clone https://github.com/SamYStudiO/es-theme-next-pixel.git

Then, from the Recalbox start menu, select UI Settings > Theme > Theme Set, and select the ES-THEME-NEXT-PIXEL-V2-4X4-240P theme from the menu. I also like to set the On-Screen Help to off, as the font is so small, and it's not hard to memorise the few UI controls.

Other Polish

In the UI Settings > Popup Settings menu, I set Help Popup Duration to 1 second, and Music Popup Duration to 0 seconds to hide music popups.

Recalbox menu controls default to a PSX style layout, but as we have a Nintendo style layout, you can also set Swap Validate/Cancel Buttons in the UI settings to On.

The Start and Home buttons are incredibly close together on the GPiCase 2, and if your thumbs are as large as mine, it can be easy to accidentally hit both buttons at once, which happens to be the Exit hotkey. In Game Settings, we can set Press Twice To Quit Game to On, this will show a popup and require a second press to quit the game - a real frustration saver!

To use the scraper, you will need an internet connection. I've found that the easiest way to achieve this, is to plug your phone into the USB-C port at the bottom, using a USB to USB-C adaptor, and use your phones USB hotspot tethering.