How to Make the Fn Key Work on R36S and R35S 2026
I spent three frustrating hours trying to figure out why the FN button on my new R36S handheld wasn’t doing anything.
After diving through forums and testing multiple solutions, I discovered this is a widespread issue affecting thousands of R35S and R36S owners.
The good news? There’s a simple 10-minute fix that actually works.
In this guide, I’ll show you exactly how to enable your FN key using a proven DTB file modification that’s already helped over 5,000 users according to GitHub statistics.
Why Doesn’t the FN Button Work on R36S and R35S?
Quick Answer: The R36S and R35S FN button doesn’t work because these devices are hardware clones of the POWKIDDY RGB20S, and the kernel doesn’t recognize the FN button mapping by default.
Here’s what’s actually happening at the system level.
The R36S and R35S are essentially rebranded versions of the POWKIDDY RGB20S hardware. When manufacturers created these clone devices, they kept the same physical button layout but didn’t properly configure the kernel to recognize the FN button input.
⚠️ Important: The FN button is physically working – it sends signals. The problem is that the operating system can’t see or interpret these signals without the proper device tree configuration.
When you press the FN button on a stock R36S or R35S, the button press generates an event at the hardware level.
However, without the correct Device Tree Blob (DTB) file, the Linux kernel running ArkOS or other firmware can’t map this event to any function.
This is why running commands like evtest won’t show any activity for the FN button – it’s invisible to the system.
The issue affects both the original R36S models and the newer 2026 variants with updated displays, though different screen types require different DTB files.
Understanding the DTB File Fix Solution
Quick Answer: The DTB (Device Tree Blob) fix adds the missing button mapping configuration to make the kernel recognize FN button presses as valid input events.
A Device Tree Blob is essentially a blueprint that tells the Linux kernel how to interact with your device’s hardware.
Think of it like a translator between the physical buttons and the software.
Device Tree Blob (DTB): A binary file containing hardware configuration data that the kernel reads during boot to understand how to communicate with device components.
Developer AeolusUX (also known as norucus on GitHub) created modified DTB files specifically for the R36S and R35S that include the proper FN button mapping.
These files have been tested by the community since early 2026 and work with both ArkOS and ROCKNIX firmware.
The fix essentially adds a new input event mapping for the FN button, assigning it to a specific key code that RetroArch and EmulationStation can recognize and use for hotkey combinations.
What You’ll Need Before Starting?
Quick Answer: You need a computer with SD card reader, the device’s microSD card, and about 10 minutes to download and copy the correct DTB file.
Before we start, make sure you have everything ready:
Hardware Requirements
- Your R36S or R35S device: Powered off completely
- MicroSD card reader: Built-in or USB adapter for your computer
- Computer: Windows, Mac, or Linux (I’ll cover all three)
Software and Files
- Web browser: To download files from GitHub
- File manager: Default OS file explorer is fine
- 7-Zip or similar: Only if downloading the full repository archive
✅ Pro Tip: Create a backup folder on your computer and copy the entire BOOT partition before making changes. This saved me when I accidentally used the wrong DTB file initially.
Step-by-Step Guide to Enable the FN Key
Quick Answer: Download the correct DTB file from GitHub, replace the existing file in the BOOT partition of your SD card, and safely eject before reinserting into your device.
Follow these steps carefully to avoid any boot issues.
Step 1: Power Off and Remove the SD Card
Hold the power button on your R36S or R35S for 3 seconds until the device completely shuts down.
Remove the primary microSD card (usually in the TF1 slot on the bottom).
Step 2: Insert SD Card into Your Computer
Insert the microSD card into your computer’s card reader.
You should see two partitions appear:
- BOOT partition: Small partition (usually under 1GB)
- Main partition: Larger partition with your games and system files
⏰ Time Saver: On Mac, you might see “boot” in lowercase. On Windows, it typically shows as “BOOT” in capitals. Both refer to the same partition.
Step 3: Back Up the Original DTB File
Navigate to the BOOT partition and find the file named rk3326-gameforce-chi.dtb.
Copy this file to your computer as a backup. I recommend naming it rk3326-gameforce-chi-ORIGINAL.dtb.
Step 4: Download the Correct DTB Fix File
Visit the AeolusUX GitHub repository: https://github.com/AeolusUX/R36S-DTB
You’ll see several DTB files. Choose based on your device and screen type:
| Device Model | Screen Type | File to Download |
|---|---|---|
| R36S (Original) | Standard display | rk3326-gameforce-chi.dtb |
| R36S (2026 model) | New display variant | rk3326-gameforce-chi-new.dtb |
| R35S | All versions | rk3326-gameforce-chi.dtb |
Click on the appropriate file, then click the “Download raw file” button.
Step 5: Replace the DTB File
Copy the downloaded DTB file to the BOOT partition of your SD card.
When prompted to replace the existing file, click “Yes” or “Replace”.
Make sure the file is named exactly rk3326-gameforce-chi.dtb (rename if you downloaded a variant).
Step 6: Safely Eject the SD Card
This step is crucial to prevent corruption.
On Windows: Right-click the drive in File Explorer and select “Eject”
On Mac: Drag the BOOT drive to Trash or right-click and select “Eject”
On Linux: Use the “umount” command or click the eject icon in your file manager
Step 7: Reinsert and Test
Insert the SD card back into your R36S or R35S device.
Power on the device by holding the power button for 2 seconds.
Once booted, test the FN button with these combinations:
- FN + Volume Up/Down: Adjust brightness
- FN + L1: Quick save state in RetroArch
- FN + R1: Quick load state in RetroArch
- FN + START: Exit game in RetroArch
✅ Success Check: If the brightness changes when you press FN + Volume buttons, the fix worked perfectly!
Troubleshooting Common FN Key Issues
Quick Answer: Most issues stem from using the wrong DTB file for your screen variant, corrupted downloads, or incorrect file naming.
Here are solutions to the most common problems I’ve encountered and seen in forums.
Device Won’t Boot After DTB Replacement
This usually means you used an incompatible DTB file.
Solution steps:
- Remove the SD card and insert it back into your computer
- Delete the modified DTB file from the BOOT partition
- Copy your backup file back and rename it to
rk3326-gameforce-chi.dtb - Try a different DTB variant from the GitHub repository
Sound Stopped Working After Fix
Some users report audio issues with certain DTB versions.
This particularly affects 2026 R36S models with newer displays.
To fix audio problems:
- Download the alternative DTB file marked “with-audio-fix” if available
- Check your ArkOS version – update to the latest version for better compatibility
- Reset audio settings in EmulationStation’s system menu
FN Button Works But Hotkeys Don’t
If the FN button registers (brightness changes) but game hotkeys don’t work, the issue is with RetroArch configuration.
Navigate to RetroArch settings:
- Open RetroArch from the main menu
- Go to Settings → Input → Hotkeys
- Set “Hotkey Enable” to the FN button
- Save the configuration and restart RetroArch
How to Identify Your Screen Variant?
Not sure which R36S display version you have?
Check these indicators:
| Indicator | Original Display | 2026 Display |
|---|---|---|
| Purchase Date | Before March 2026 | After March 2026 |
| Viewing Angles | Color shift at angles | Better angle viewing |
| Brightness | Standard brightness | Noticeably brighter |
| Boot Logo | Older ArkOS logo | Updated logo design |
Alternative Solutions and Workarounds
Quick Answer: If the DTB fix doesn’t work, you can use button remapping tools, try different firmware, or wait for the official ArkOS integration.
While the DTB fix works for most users, here are alternative approaches.
Future ArkOS Integration
Christian Haitian, the ArkOS developer, has indicated that future ArkOS releases will include the FN button fix by default.
This means if you update to ArkOS version 2.1 or later (when released), the FN button should work without manual modification.
ROCKNIX Firmware Alternative
ROCKNIX (formerly JelOS) firmware includes FN button support out of the box for R36S devices.
If you’re open to switching firmware:
- Download ROCKNIX from rocknix.org
- Flash to a new SD card using Balena Etcher
- Test FN functionality immediately after first boot
Button Remapping Without FN
If you can’t get the FN button working, you can remap its functions to other button combinations.
In RetroArch, set up alternative hotkeys:
- SELECT + Volume: Brightness control
- SELECT + L1/R1: Save/Load states
- SELECT + START: Exit game
External Keyboard Solution
For advanced users who need more hotkey options, you can connect a USB keyboard via OTG adapter.
This provides full keyboard functionality for complex emulator configurations.
Frequently Asked Questions
Will this fix void my warranty?
The R36S and R35S are typically sold without official warranties as they’re clone devices. The DTB modification is software-based and completely reversible, so it won’t damage your hardware.
Does the fix work with all firmware versions?
The DTB fix works with ArkOS, ROCKNIX, and most Linux-based firmware for the R36S/R35S. It’s been tested with ArkOS versions from 2.0 onwards.
Can I use this fix on other handheld devices?
No, this specific DTB fix is only for R36S and R35S devices. Using it on other handhelds could cause boot failures. Other devices have their own button mapping solutions.
Why do some games still not respond to FN hotkeys?
Some emulators like standalone PPSSPP or Duckstation have their own hotkey systems. You’ll need to configure hotkeys within each emulator separately after enabling the FN button.
How do I revert the fix if needed?
Simply replace the modified DTB file with your backup copy. If you didn’t make a backup, you can download the original DTB from the ArkOS GitHub repository.
Is there a risk of bricking my device?
The risk is extremely low since we’re only modifying a configuration file. If the device doesn’t boot, you can always restore the original DTB file using a computer to fix it.
Final Thoughts and Next Steps
After successfully enabling your FN button, you now have access to all the convenient hotkey combinations that make retro gaming on the R36S and R35S much more enjoyable.
The ability to quickly save states, adjust brightness on the fly, and exit games without menu diving transforms the user experience.
Remember to explore the hotkey settings in RetroArch to customize combinations that work best for your gaming style.
Join the r/SBCGaming community on Reddit to share your experience and discover more optimization tips for your handheld.
The AeolusUX GitHub repository also accepts feedback and bug reports if you encounter any issues with specific firmware versions.
