How to install MuOS on Anbernic RG35XX?

MuOS is a custom firmware for RetroArch only system, available to the popular handheld Anbernic RG35XX. Adixal, the author of this custom firmware is a big fan of RetroArch and RGUI way back in the day RG35XX didn’t have a proper system like how the Miyoo Mini Plus had Onion OS. Today, I will write a quick guide on how to install MuOS on RG35XX.

I also recommend to check my RG35XX custom firmware comparison, in case you want to see how MuOS compares to other popular RG35XX’s systems like Garlic or MinUI.

As usual, I give my thanks to adixal for all of his contribution to the community of the Anbernic RG35XX. Not only did he make MuOS, he also brought applications for the more popular Garlic, which you may be more familiar with, by reading my RG35XX Garlic installation guide.

What you need

• The latest version of SD Formatter
• The latest version of guiformat
• The latest version of Rufus
• The latest version of 7zip
• The latest version of MuOS (version 2310w)

How to install MuOS on Anbernic RG35XX

To run MuOS on Anbernic RG35XX, you need to pre-format your microSD card first. There is usually SD cards included with the Anbernic RG35XX, but they are no-brand card with high chance to fail. You should read my handheld SD card guide, to know which SD card you should choose (quite a long guide).

If you’re going to use 2 SD cards for installing MuOS on RG35XX, you need to pre-format both SD cards as FAT32.

Step 1: Preparing the microSD card

You need to format your microSD cards as FAT32. Remember that this is not the same format as exFAT. You must format every SD card that you would like to use with the Anbernic RG35XX.

Formatting a microSD card (Windows)

• For microSD cards 32GB or smaller: You should use SD Formatter
  1. Insert your SD card into your computer with an SD card reader
  2. If the microSD card has any files or folders, copy them all to a folder on your computer
  3. Run SD Card Formatter Setup (the .exe file) in the downloaded .zip file as Administrator, then install the program
  4. Run SD Card Formatter from the Start Menu
  5. Select your SD card’s drive letter for “Select card”. Make sure you pick the right drive letter, or you might erase the wrong drive by accident
  6. Enter anything for “Volume label”
  7. Ensure that “Quick Format” is selected
  8. Click “Format”. Then click “OK”. Wait for the format to finish
  9. Click “OK”
• For microSD cards 64GB or larger: You could use the latest version of guiformat
  1. Insert your microSD card into your computer, you can use the default SD card reader included in RG35XX package
  2. If the microSD card has any files or folders, copy them all to a folder on your computer
  3. Run guiformat.exe
  4. Select your SD card’s drive letter for “Select card”. Make sure you pick the right drive letter, or you might erase the wrong drive by accident
  5. Select a size for “Allocation unit size”:
     • If the microSD card is 64GB, choose 32768
     • If the microSD card is larger than 64GB, choose 65536
  6. Enter anything for “Volume label”
  7. Ensure that “Quick Format” is selected
  8. Click “Start”. Then click “OK”. Wait for the format to finish
  9. Click “Close”

Formatting a microSD card (Mac)

• OS X El Capitan (10.11) and later
  1. Insert your microSD card into your computer
  2. If the microSD card has any files or folders, copy them all to a folder on your computer
  3. Run the Disk Utility app
  4. In the top-left “View” menu, choose “Show All Devices”
  5. Select your SD card in the left panel. Make sure you pick the right drive letter, or you might erase the wrong drive by accident
  6. Click “Erase” at the top
  7. Enter anything for “Name”
  8. Ensure that “Format” is set to “MS-DOS (FAT)”
  9. Ensure that “Scheme” is set to “Master Boot Record”
     • If “Scheme” does not appear, click “Cancel” and make sure to choose the device instead of a volume
  10. Click “Erase”. Wait for the format to finish
  11. Click “Close”
• OS X Yosemite (10.10) and earlier
  1. Insert your microSD card into your computer
  2. If the microSD card has any files or folders, copy them all to a folder on your computer
  3. Run the Disk Utility app
  4. Select your SD card in the left panel. Make sure you pick the right drive letter, or you might erase the wrong drive by accident
  5. Click “Partition” at the top. If “Partition” does not appear, make sure to choose the device instead of a volume
  6. Ensure that “Partition Layout” is set to “1 Partition”
  7. Enter anything for “Name”
  8. Ensure that “Format” is set to “MS-DOS (FAT)”
  9. Click “Options” below the partition table. Choose “Master Boot Record”
  10. Click “OK”
  11. Click “Apply”
  12. Click “Partition”. Wait for the format to finish
  13. Close Disk Utility

Step 2: Add MuOS image on SD card

Download MuOS as I listed on prerequisite section, then extract the compressed file with 7zip. Now you can add MuOS image to your SD card using Rufus.

• Open Rufus, select Device to be your SD card. In Boot selection, choose muos.img that you previously downloaded.
• Click START. Then click OK. The process of writing MuOS to your SD card needs 5-10 minutes to be done.
• Don’t format any partitions after that.
• Insert the SD card into RG35XX (TF1 slot), power it up. The first boot will automatically initialize everything, and expand the missing storage for your partition

MuOS automatically generate a partition for your own BIOS and Roms in the SD card on TF1 slot (for single-SD-card installation) or TF2 slot (for dual-SD card installation). If you don’t know which ROM files to add, read my in-depth guide of ROM folder names to copy your games into the partition.

RG35XX’s MuOS features

Like I said in my RG35XX custom firmware comparison, MuOS tends to be a low-profile custom firmware for who want a simple system. Still, there are many features to explore on the latest version of MuOS:

1. Pure RetroArch menu, with redesigned RGUI
2. Boot animation support
3. Low battery notification
4. Idle screensaver for screen blanking
5. Added progress bar for factory reset process
6. Support muting with shortcuts (SELECT + DOWN), named JoyAudio
7. Support adjusting brightness with shortcut (holding SELECT and pressing volume up and down), named JoyBright

That’s it, if you have any other questions, please find it in my RG35XX tutorial.