The WasmSequencer copies serial writes through a buffer of serialOutMax bytes (256 in the harness) and traps a longer payload with BufferTooLarge, while the FpySequencer sends any size straight from its stack. The limit is a WasmSequencer::configure value that is not in the dictionary, so the compiler has no way to check it today.
x: Svc.SeqArgs = Svc.SeqArgs()
write_to_port(Svc.Fpy.SerialPortIndex.EXAMPLE_PORT_0, x) # 263 bytes: fpybc ok, wasm traps
The WasmSequencer copies serial writes through a buffer of
serialOutMaxbytes (256 in the harness) and traps a longer payload withBufferTooLarge, while the FpySequencer sends any size straight from its stack. The limit is aWasmSequencer::configurevalue that is not in the dictionary, so the compiler has no way to check it today.