MIROKI

A standalone custom firmware for the Anbernic RG Rotate (Unisoc T618, ums512). It boots from the internal eMMC, with no SD card needed, straight into RetroArch with ramen, a menu built for the swivel screen that puts the games first. It covers the 5th generation: N64 (mupen64plus), PlayStation (PCSX ReARMed) and Saturn (YabaSanshiro).

The boot chain is a rebuilt Unisoc SPL and a small EL3 monitor of our own, then a mainline-based kernel and a squashfs root. The stock firmware's secure world and u-boot are not used.

AI Disclaimer

Claude Code was used here, like a bunch.

Previews

Systems	Games
In-Game Menu

Building

Host

Ubuntu 24.04 or a derivative, on x86_64. The kernel, the boot chain and the rootfs are cross-built with Ubuntu's AArch64 toolchain. RetroArch links against Ubuntu's arm64 libraries through multiarch: arm64 packages come from ports.ubuntu.com, so add that as an arm64-only apt source first if your system has none.

sudo dpkg --add-architecture arm64
sudo apt update
sudo apt install build-essential gcc-aarch64-linux-gnu g++-aarch64-linux-gnu \
    bc bison flex libssl-dev kmod python3 rsync squashfs-tools \
    autoconf automake libtool pkgconf pkgconf:arm64 \
    libasound2-dev:arm64 libdrm-dev:arm64 libegl-dev:arm64 \
    libgles-dev:arm64 libgbm-dev:arm64 libudev-dev:arm64 \
    libxkbcommon-dev:arm64 zlib1g-dev:arm64

Sources

The components are git submodules under ext/:

git clone --recurse-submodules <this repository>
cd rg-rotate

In an existing checkout, git submodule update --init --recursive fetches them. PCSX ReARMed needs its own nested submodules, which --recursive covers.

Build

make

builds everything into build/cfw. Each step is also a target of its own, which runs one script from tools/:

Target	Output	eMMC partition
make spl	build/cfw/splloader.img	splloader
make boot	build/cfw/boot.img	boot
make retroarch	build/cfw/retroarch/
make cores	build/cfw/cores/
make rootfs	build/cfw/rootfs.squashfs	rootfs

make rootfs packs what the others built: the kernel modules from make boot, RetroArch and the cores. After a kernel change, rebuild both boot and rootfs, so the modules match the kernel.

make clean removes build/. make distclean also cleans the builds that happen inside the submodules (the kernel, busybox, RetroArch, the cores and the SPL). JOBS=n limits parallelism.

Flashing

INSTALLING MIROKI WILL OBLITERATE ANDROID FROM YOUR RG ROTATE AND DOES NOT SUPPORT DUAL BOOTING!!!

SERIOUSLY, YOU HAVE BEEN WARNED!!!

Flashing uses the BootROM's download mode and tools/spd_dump, with the device's download stubs (fdl1-dl.bin, fdl2-dl.bin) next to it. To enter download mode, hold the Home/Back combo button while plugging in USB; the host should then see a 1782:4d00 device.

Writing the SPL or the partition table can brick the device, short of BootROM recovery. Keep a full backup of the stock firmware.

The first flash repartitions the eMMC user area to MIROKI's layout (tools/cfw-emmc-partitions.xml) and writes all three images:

cd tools
./spd_dump --wait 300 keep_charge 1 \
  fdl fdl1-dl.bin 0x5500 \
  fdl fdl2-dl.bin 0x9EFFFE00 \
  exec \
  repartition cfw-emmc-partitions.xml \
  write_part splloader ../build/cfw/splloader.img \
  write_part boot ../build/cfw/boot.img \
  write_part rootfs ../build/cfw/rootfs.squashfs \
  poweroff

After that, flash only what changed: leave out repartition, and write just the partitions you rebuilt. exec must come after the two fdl loads and before any write, and poweroff comes last. FDL2: incompatible partition is harmless.

First boot

On the first boot the data partition is formatted as exFAT. It holds everything that changes: ROMs, saves, states and RetroArch's settings.

• ROMs go in roms/n64, roms/psx and roms/saturn.
• BIOS files go in bios. The Saturn core needs one of saturn_bios.bin, sega_101.bin or mpr-17933.bin; the PlayStation core has a built-in BIOS and can use a real one.
• Boxart optionally goes under roms/<system>/boxart with each file matching the name of its corresponding game, minus its extension. Accepted formats are .png and .jpg/.jpeg.
• Extra libretro cores can go in cores, as aarch64 Linux builds named <name>_libretro.so. Each becomes a system that reads roms/<name>; with a matching <name>_libretro.info beside it, it also reads roms/<systemid>, the systemid from that file. Make those folders yourself. A core named like a built-in one (pcsx_rearmed_libretro.so), or whose name or systemid is n64, psx or saturn, replaces that built-in core. Cores must render in software or through GLES, and need only the libraries already on the device.

An SD card is optional. If one is in (exFAT or FAT), its top-level bios, cores and roms folders are read alongside the ones on data, laid out the same way; where both have the same BIOS or core file, data's is used. Saves, states and settings always stay on data.

Press Start in the system carousel for Storage Mode: the device shares data with the computer as a USB drive and unmounts the SD card, so the card can be taken out or swapped. It leaves Storage Mode when the computer ejects the drive (or on Start again), then mounts whatever card is in and reads everything again.

Controls

Input	Action
AUX	Open the menu (also in game)
Mode + R1 / L1	Save / load state
Mode + R2	Fast-forward on/off
Mode + Right / Left	Next / previous state slot
Start, in the carousel	Storage Mode
Volume keys	Volume
Mode + volume keys	Screen brightness
Power, short press, or closing the swivel	Sleep
Power, held for 2 s	Power off (with a short buzz)

Console

The device side of USB also carries a serial console. On the computer:

sudo modprobe cdc_acm
picocom -b 115200 /dev/ttyACM0

If ModemManager runs on the computer, it probes the port as a modem and its AT commands end up as garbage at the device's shell; stop it from claiming the port with a udev rule.

Layout

Path	What
ext/boot/spl	The SPL and the EL3 monitor (PSCI)
ext/boot/linux	The kernel
ext/retroarch/	RetroArch and the three cores
ext/system/	busybox, exfatprogs, libudev-zero, the Mali kernel driver
system/	MIROKI's own code: the initramfs, the rootfs files, ramen, the input daemon, small audio tools, prebuilt firmware and GPU blobs
tools/	The build scripts, the kernel config, the partition layout and spd_dump