How to install KNULLI on RG35XX H and TRIMUI Smart Pro (2025 guide)

KNULLI is a feature-rich custom firmware based on Batocera Linux, supporting a wide range of budget retro handhelds. If you want RetroAchievements, artwork scraping, Wi-Fi features, and a polished interface — KNULLI delivers all of that on devices where GarlicOS or MinUI fall short.

What is KNULLI?

KNULLI is a community-maintained distribution built on Batocera Linux. It supports more devices than most other custom firmware options and brings a consistent experience across all of them. Think of it as the “everything included” option: extensive emulator support, network features, scraper for box art, and regular updates.

For a full comparison of firmware options, see our custom firmware comparison guide or the KNULLI firmware tracker for the latest version.

Compatible devices

KNULLI officially supports:

• Anbernic RG35XX H ✅
• Anbernic RG28XX ✅
• TRIMUI Smart Pro ✅
• Additional Anbernic and TRIMUI devices (check the official KNULLI site for the full list)

This guide covers the RG35XX H, RG28XX, and TRIMUI Smart Pro. The process is identical across all three.

What you’ll need

• A supported device — RG35XX H, RG28XX, or TRIMUI Smart Pro
• MicroSD card — 32GB minimum, 64–128GB recommended (Samsung or SanDisk)
• SD card reader for your computer
• Computer (Windows, Mac, or Linux)
• Game ROMs — legally obtained from cartridges you own

Time required: ~25 minutes

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KNULLI vs GarlicOS vs MinUI — which should you choose?

	KNULLI	GarlicOS	MinUI
Interface	Batocera-style, polished	Simple, minimal	Ultra-minimal
RetroAchievements	✅	✅	❌
Wi-Fi / network	✅ (where hardware supports)	❌	❌
Artwork scraping	✅	❌	❌
Battery life	⭐⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐⭐⭐
Update frequency	Regular	Occasional	Occasional
Best for	Feature seekers	Speed & simplicity	Minimalists

Choose KNULLI if: you want RetroAchievements, artwork scraping, or a feature-rich experience.
Choose GarlicOS if: you want the fastest, most battery-efficient option with minimal setup.

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Step 1: Download KNULLI

1. Go to the official KNULLI GitHub releases page
2. Find the latest release and download the correct image for your device:
   • RG35XX H → look for knulli-*-rg35xx-h.img.gz or similar
   • RG28XX → look for knulli-*-rg28xx.img.gz
   • TRIMUI Smart Pro → look for knulli-*-trimui-smart-pro.img.gz
3. Also check the official KNULLI website for device-specific installation notes

⚠️ KNULLI releases are device-specific. Download the exact image for your device — using the wrong image will not work.

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Step 2: Flash the image to your SD card

KNULLI uses a full disk image, so you need to flash it directly to the SD card.

Using Balena Etcher (recommended — all platforms):

1. Download Balena Etcher (free, Windows/Mac/Linux)
2. Insert your MicroSD card
3. Open Etcher → Flash from file → select the .img.gz file you downloaded
4. Select your SD card as the target
5. Click Flash and wait for completion (~10–15 minutes depending on card speed)
6. Etcher will verify the flash automatically

Using Raspberry Pi Imager (alternative):

1. Download Raspberry Pi Imager
2. Choose Use custom and select your KNULLI .img.gz file
3. Select your SD card and click Write

Using dd (Linux/Mac advanced users):

# Replace /dev/sdX with your SD card device
gunzip -c knulli-*.img.gz | sudo dd of=/dev/sdX bs=4M status=progress
sync

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Step 3: First boot and initial setup

1. Insert the flashed SD card into your device
2. Power on
3. KNULLI will boot and perform first-time setup — this takes 2–5 minutes as it expands the filesystem
4. Do not power off during this process
5. The device will reboot automatically when setup is complete

You’ll land on the Batocera-style main menu (EmulationStation). KNULLI is ready to configure.

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Step 4: Connect to Wi-Fi (optional but recommended)

Wi-Fi enables artwork scraping, RetroAchievements, and save sync. Note: the RG35XX H and RG28XX do not have built-in Wi-Fi hardware — this step applies to the TRIMUI Smart Pro and other Wi-Fi-capable devices.

1. Go to Main Menu → Network Settings
2. Enable Wi-Fi
3. Select your network and enter the password
4. KNULLI only supports 2.4GHz networks

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Step 5: Add your ROMs

Option A: Via SD card (recommended)

1. Power off the device
2. Remove the SD card and insert it into your computer
3. Navigate to the roms/ folder — you’ll see subfolders for each system
4. Copy your ROM files into the appropriate folders:

Platform	Folder	Accepted Formats
Game Boy	roms/gb/	.gb, .zip
Game Boy Color	roms/gbc/	.gbc, .zip
Game Boy Advance	roms/gba/	.gba, .zip
NES	roms/nes/	.nes, .zip
SNES	roms/snes/	.sfc, .smc, .zip
Sega Genesis	roms/megadrive/	.md, .gen, .zip
PlayStation 1	roms/psx/	.bin/.cue, .pbp, .chd
PSP	roms/psp/	.iso, .cso
N64	roms/n64/	.z64, .n64, .zip

5. Safely eject and reinsert the SD card
6. Power on — KNULLI will scan for games automatically

Option B: Via network share (Wi-Fi devices only)

1. Connect KNULLI to Wi-Fi (Step 4)
2. On your computer, open a file manager and connect to \\KNULLI (Windows) or smb://knulli (Mac)
3. Copy ROMs directly to the network share — no SD card removal needed

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Step 6: Add BIOS files

Some emulators require BIOS files:

System	BIOS File	Required?
PS1	scph1001.bin	✅ Yes
GBA	gba_bios.bin	Recommended
NDS	bios7.bin, bios9.bin, firmware.bin	✅ Yes

Copy BIOS files to the bios/ folder on your SD card.

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Step 7: Scrape artwork (optional)

KNULLI includes a built-in scraper that downloads box art and metadata for your games:

1. Go to Main Menu → Scraper
2. Select ScreenScraper as the source (free account required at screenscraper.fr)
3. Enter your ScreenScraper credentials
4. Select which systems to scrape
5. Click Start — scraping runs in the background

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Step 8: Set up RetroAchievements

1. Go to Main Menu → RetroAchievements
2. Enter your RetroAchievements username and password (free account at retroachievements.org)
3. Enable Hardcore Mode if you want leaderboard eligibility
4. Achievements will now appear in-game for supported titles

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Pixel scaling on KNULLI

The RG35XX H’s 640×480 screen is ideal for classic gaming. To enable integer scaling in KNULLI:

1. Launch a game
2. Press Select + B (or your configured hotkey) to open the RetroArch menu
3. Go to Settings → Video → Scaling
4. Enable Integer Scale

Use our Screen Visualizer to preview how each platform looks on the RG35XX H before playing.

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Troubleshooting

Device won’t boot after flashing

• Re-flash the SD card — verify Etcher completed without errors
• Try a different, higher-quality SD card
• Confirm you downloaded the correct image for your specific device model

Games aren’t showing up

• Confirm ROMs are in the correct subfolders (KNULLI uses lowercase folder names)
• Go to Main Menu → Game Settings → Update Game List to force a rescan
• Check that your ROM format is supported

Wi-Fi won’t connect

• KNULLI only supports 2.4GHz networks
• Ensure your password is entered correctly
• Move closer to your router during initial setup

Artwork scraping fails

• Verify your ScreenScraper account credentials
• ScreenScraper has daily rate limits — try again the next day if you hit the limit
• Check your Wi-Fi connection is stable

RetroAchievements not working

• Verify your credentials in Main Menu → RetroAchievements
• Ensure the game is supported (check retroachievements.org)
• Some cores don’t support achievements — try a different core for the same system

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What to do next

• Check the KNULLI firmware tracker for the latest version and changelog
• Use the Screen Visualizer for pixel-perfect scaling setup
• See full device specs: RG35XX H · RG28XX · TRIMUI Smart Pro
• Compare devices in our compatibility matrix

Related guides:

• How to install GarlicOS — lighter alternative for RG35XX H
• How to install OnionOS — for Miyoo Mini Plus users
• GarlicOS vs OnionOS vs KNULLI comparison
• What is custom firmware?