Retroflag GPi 2 with Dock (CE08464)

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Travel back to the Retro days with the GPi 2 case, grab a CM4 and start playing the classics!

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We’ve found there are a few common pitfalls when setting up the GPi 2 case so here’s a quick step-by-step process and the symptoms of common issues.

  1. Flash your SD card using Raspberry Pi Imager with your choice of Recalbox or RetroPie (found in the Emulation and game OS submenu). Choose the Pi4/400 version as it’s most similar to the CM4.

  2. Download the GPi 2 display patch from Retroflag’s website or the link below.
    This patch causes the display to default to the GPi 2 LCD instead of HDMI

  3. unzip the patch and follow the instructions in the readme file which are:

  • copy the folder matching your OS image into the root directory of your SD card
  • open the patch folder on the SD card and run install_patch.bat
  1. You can now fit the SD card to the GPi 2 case, the top of the SD card holder swings out from the PCB. Slide it down slightly to unlock, add your SD card then press gently and slide up to lock the SD in place.

  2. Fit your CM4 to the GPi 2 case by orienting it to match the white trace lines with the component clusters on the CM4. There are two connectors that need to be pressed in until they lock with the GPi 2 case. The GPi 2 is shown with the back case removed below for better visibility of the outlines and connectors.

  3. You can now boot up the GPi 2 and install the safe shutdown scripts using the instructions found here GitHub - RetroFlag/GPiCase2-Script: RetroFlag GPiCase 2 CM4 Safeshutdown with automatically switch LCD and HDMI display script

Common issues:

Symptom: No display on GPi 2 LCD
Cause: GPi 2 patch is not installed, or CM4 connectors may not be fully seated.

Symptom: No response from GPi 2 at all, backlight is not lit.
Cause: GPi 2 battery may be flat.

Symptom: GPi 2 display works but doesn’t switch to HDMI when placed into dock
Cause: The HDMI is not hot-swappable on the GPi 2, you need to power the GPi 2 down, fit the dock, then reboot it to use the dock’s HDMI output.

Symptom: Display is rotated sideways and odd white lines on half of display
Cause: GPi 1 patch was installed on GPi 2 case (don’t ask me how I know).


If you are using a Compute Module 4 that has eMMC memory on board there are a few extra steps to setup your GPi 2.

You can’t use the SD card holder if your CM4 has eMMC memory, you need to write the OS image to the eMMC on the CM4 directly instead. To do this you need to mount the eMMC memory as a drive on your computer.

  1. Fit the CM4 into the GPi 2 case so it matches the silkscreen outlines on the case, you should hear a click for both connectors as they snap into place

  2. Turn on the GPi 2 case at the power switch then plug it into a computer using the USB port in the back of the GPi 2.

  1. Download and install the USB boot utility for windows. (If you’re using a non-windows computer see this other guide which goes over some alternatives briefly)

  2. Run the rpiboot application, you should see a console come up and your computer should detect a new drive and give a message about needing to format it(you don’t need to, we’ll handle that next)

  3. Install and run Raspberry Pi Imager selecting your chosen OS for the GPi 2 and selecting the mounted CM4 as the storage.

  4. Once the CM4 has finished flashing you can continue from step 2 in the post above, ignoring anything that mentions the SD card.

Common Issues for eMMC CM4s:

Symptom: rpiboot does says Waiting for BCM2835/6/7/2711… and does not mount the drive

  • Check the CM4 is properly clipped into both connectors of the GPi 2 case
  • Check the case is powered on and has battery charge
  • Check that the microUSB cable you have connected to your computer and case is not a charge-only cable without data pins.

Just got my GPI case, installed Recalbox and can get display on the dock and it boots to the OS but nothing displays on the screen when it isn’t docked. Is there anything I can to do to troubleshoot this?

Hey @Ash259577

That’s a tricky one, can we confirm that you used the correct image and process to install recalbox?

Their website is great for finding the right one:

Figured it out! I just had to redo the install after that it worked.

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