gen1recomp/docs/linux-arm-sbc.md

Linux ARM SBC Handhelds (PortMaster)

Download gen1recomp-*-sbc-portmaster.zip from the Gen1Recomp releases. This build targets 64-bit Linux ARM handhelds with PortMaster, including compatible H700 devices.

Install

1. Unzip the release. It contains gen1recomp-sbc.sh and a gen1recomp-sbc/ folder.
2. Copy both as siblings into your device's PortMaster ports directory, commonly Roms/Ports (PORTS)/ or Roms/PORTS/.
3. Install PortMaster for your firmware and refresh the Ports list.
4. Copy your legally owned canonical US Red or Blue .gb file into gen1recomp-sbc/lovegame/.
5. Launch gen1recomp-sbc from Ports and choose the ROM.

The pack includes portable.txt, so saves and ROM-derived cache remain beside the game on the SD card. The build never ships ROM-derived bytes.

Canonical US cart SHA-1 values:

• Red: ea9bcae617fdf159b045185467ae58b2e4a48b9a
• Blue: d7037c83e1ae5b39bde3c30787637ba1d4c48ce2

Updating

The port updates itself from the launcher. When a newer release exists the footer chip reads Update vX.Y.Z: press it to download the new version, then press Restart to update to relaunch and start using it. Nothing inside the port folder is rewritten, so an update that fails or is interrupted still boots the version you already had.

An update replaces the game's code and data. It cannot replace the LÖVE runtime the port ships, so a release that needs a newer runtime is applied differently: the chip then reads Download port update and saves gen1recomp-<version>-sbc-portmaster.zip into

gen1recomp-sbc/conf/love/pokemon-love2d/updates/

That case is finished on a computer — unzip the file and copy the gen1recomp-sbc.sh and gen1recomp-sbc/ it contains over the copies on the SD card, exactly as in Install above. Your saves sit beside the game (portable.txt) and are untouched by either kind of update.

The launcher exports POKEPORT_PORTMASTER=1, which is how the updater knows this is the PortMaster port and offers the port package rather than a desktop AppImage.

Controls

Input	Action
D-pad	Move cursor
A	Click / confirm
L1 / R1	Switch tabs
Start / Select	Play or choose ROM

In-game controls use the normal PortMaster/SDL mapping and can be rebound in OPTIONS → CONTROLS.

Runtime and suspend

The package bundles PortMaster's LÖVE 11.5 aarch64 runtime. The launcher sources control.txt, calls get_controls, applies an optional CFW override, invokes pm_platform_helper, and calls pm_finish on exit. Paths are relative to the launcher, allowing different firmware mount points.

Suspend/resume uses the existing LÖVE focus/visibility lifecycle: input is reset on focus loss and the game resumes when the window becomes visible again. Exact power-button behavior remains firmware-dependent; hardware validation has been performed on the TrimUI Brick, not every SBC or H700 device.

Power and Performance Tuning

The handheld build applies several optimizations to reduce power draw while keeping smooth frame pacing on low-power ARM SoCs:

• PresentSync / driver vsync: Handheld builds keep driver vsync enabled so the unified present-sync stack can probe cadence and pace through the panel (KMSDRM page-flip wait). Disabling vsync here bypassed that path and forced the FrameCap 1 ms polling loop at 60 FPS.
• Idle Render Governor: After POKEPORT_IDLE_AFTER seconds without input on static in-game screens, presentation drops to POKEPORT_IDLE_FPS while game logic and audio stay at full speed. Any button press restores full framerate on the next frame.
• Sample Rate Scaling: Audio synthesis is tuned to 22.05 kHz by default (POKEPORT_AUDIO_RATE=22050), halving synthesis CPU overhead on Cortex-A53 cores with no audible quality loss on handheld speakers. The synth engine and its queueable source are built for one rate, so changing PERFORMANCE across the LOW boundary in OPTIONS switches the rate live and replays the current song from the start of its section; the rate never changes on its own during play.
• Dynamic CPU Governor: Defaults to schedutil instead of pinning performance on all cores, reducing thermals and extending battery life.

Environment variables for fine-tuning (configured in gen1recomp-sbc.sh):

Variable	Default	Description
POKEPORT_IDLE_AFTER	10	Seconds without input before an idle screen drops presentation rate
POKEPORT_IDLE_FPS	6	Framerate while idle
POKEPORT_AUDIO_RATE	22050	Chip-synth sample rate (set to 44100 for full rate)
POKEPORT_CPU_GOVERNOR	schedutil	CPU scaling governor (schedutil, performance, ondemand)

Bundled LuaJIT

The pack does not use PortMaster's libluajit-5.1.so.2. That one is LuaJIT 2.1.0-beta3 (2017), which segfaulted 3 of 3 runs with the JIT on (TrimUI Brick). The pack ships a pinned LuaJIT 2.1 build instead (commit c6ffc141a8762b41703f9287d63d93622a13dd8f, MIT, license in licenses/LuaJIT-COPYRIGHT). It is compiled from source in a Debian bullseye aarch64 container (glibc 2.31, GC64, make amalg) by scripts/luajit/build_luajit.sh, and the build checks the version string and the glibc requirement before and after zipping. On the TrimUI Brick it ran a 26-minute JIT-on soak with no crash.

The JIT still stays off by default on these builds: LÖVE turns it off on arm64, and nothing here sets POKEPORT_JIT. It has only been validated on one device (TrimUI Brick, A133P). Enabling POKEPORT_JIT=1 by default needs stability testing on H700, RK3566 and A133P devices first.

The PortMaster catalogue package (scripts/portmaster/, see portmaster-submission.md) is different: it runs on the device's own PortMaster love_11.5 runtime, so it still uses that runtime's LuaJIT 2.1.0-beta3. Keep the JIT off there.

Existing installs keep their old LuaJIT until the zip is re-extracted: in-app updates replace only the game's code, not the runtime libraries.

Building the port now needs an aarch64 host with docker or podman (non-aarch64 hosts are refused), or a prebuilt library passed with GEN1RECOMP_LUAJIT_LIB=/path/to/libluajit-5.1.so.2 (with its COPYRIGHT next to it, or GEN1RECOMP_LUAJIT_COPYRIGHT). The remaining PortMaster runtime files are pinned to a PortMaster-GUI commit and sha256-checked.

For scripts that wrap build-linux-arm-sbc.sh: the library in GEN1RECOMP_LUAJIT_LIB must have a COPYRIGHT beside it (or set GEN1RECOMP_LUAJIT_COPYRIGHT) and must pass scripts/luajit/verify_luajit.sh (the pinned LuaJIT version, built with PREFIX=/usr). There is no longer any way to ship PortMaster's stock LuaJIT; a wrapper's "stock LuaJIT" mode should be removed, and the wrapper pointed at scripts/luajit/build_luajit.sh instead.

Building

Release workflows build this automatically. Standalone builds resolve the latest published Gen1Recomp release by default:

./build-linux-arm-sbc.sh --version 0.1.75

For development, package a local checkout explicitly:

GEN1RECOMP_SOURCE_DIR="$PWD" ./build-linux-arm-sbc.sh --version 0.1.0
# or: ./build-linux-arm-sbc.sh --source "$PWD" --version 0.1.0

The generated port.json records the source release tag. install-linux-arm-sbc.sh is a macOS helper for copying a built pack to a mounted SD card.

PortMaster device support and runtime integration are maintained in the PortMaster ecosystem.