romdev-platform-sync32

The sync32 SDK tree for romdev: crt0.S, the ram.ld / xip.ld linker scripts, sync32.h and an ARMv8-M libgcc.a.

sync32 is an open RP2350-based console. A game is a freestanding Cortex-M33 binary wrapped in a 64-byte header (.s32). Building one needs the crt0 (vector table and _start), the linker script for the memory mode, and the console API header. All of them are small text files, so they ship here instead of requiring a checkout of the SDK.

sync32.h defines three video modes, chosen in the cart header: 320x240 (4:3), 320x180 (16:9 letterbox) and 128x128 (shown at 3x, for 128x128 fantasy-console games). Every mode draws 8-bit indices into a 256-entry RGB565 palette.

The compiler is not in this package. sync32 carts are built with the WASM arm-none-eabi toolchain in romdev-platform-gba, the same gcc, run with -mcpu=cortex-m33 -mthumb -mfloat-abi=hard -mfpu=fpv5-sp-d16 instead of the GBA's ARM7TDMI flags. That is why this package is about 1.2MB (almost all of it libgcc) rather than the size of the compiler itself. romdevtools drives it for build({platform:'sync32'}); you normally install romdevtools (npx romdevtools).

A cart links no libc: the SDK is freestanding, so there is no printf, no malloc and no string.h. It does link libgcc, shipped here as share/sync32/lib/libgcc.a: the compiler emits calls into it for operations the CPU cannot do in one instruction, such as a 64-bit divide (__aeabi_uldivmod) or double-precision float. It must be the ARMv8-M build: the ARM archives in romdev-platform-gba are ARMv4T and cannot link with a Cortex-M33 object.

Two consequences when writing a cart:

• Prefer float to double. The FPU is single-precision only (fpv5-sp-d16), so a double compiles to soft-float library calls that are an order of magnitude slower.
• Avoid 64-bit integer division in a hot loop for the same reason: it is a library call, not an instruction.

Builds also pass -ffreestanding. Without it the compiler assumes a hosted environment and may turn a struct initializer into a memset call, which then cannot link.

License

• The SDK files (crt0.S, linker scripts, sync32.h): MIT (the package's license field).
• libgcc.a: GPL-3.0-or-later with the GCC Runtime Library Exception, so linking it does not place conditions on a compiled cart.

Built by: packages/romdevtools/scripts/build-arm-libgcc-v8m.sh (the libgcc build) in the romdev repo.