SITL running in-browser / in Configurator as WASM (web assembly) for comparison

CMakeLists.txt

@@ -12,7 +12,7 @@ set(TOOLS_DIR "${MAIN_DIR}/tools")
 
 option(SITL "SITL build for host system" OFF)
 
-set(TOOLCHAIN_OPTIONS none arm-none-eabi host)
+set(TOOLCHAIN_OPTIONS none arm-none-eabi host wasm)
 if (SITL)
     if (CMAKE_HOST_APPLE)
         set(MACOSX TRUE)

cmake/settings.cmake

@@ -37,6 +37,9 @@ function(enable_settings exe name)
     if(host STREQUAL TOOLCHAIN)
         set(USE_HOST_GCC "-g")
     endif()
+    if("wasm" STREQUAL TOOLCHAIN)
+        set(args_SETTINGS_CXX "em++")
+    endif()
     set(output ${dir}/${SETTINGS_GENERATED_H} ${dir}/${SETTINGS_GENERATED_C})
     add_custom_command(
         OUTPUT ${output}

cmake/sitl.cmake

@@ -12,19 +12,45 @@ main_sources(SITL_COMMON_SRC_EXCLUDES
 )
 
 main_sources(SITL_SRC
-    config/config_streamer_file.c
-    drivers/serial_tcp.c
-    drivers/serial_tcp.h
-    target/SITL/sim/realFlight.c
-    target/SITL/sim/realFlight.h
-    target/SITL/sim/simHelper.c
-    target/SITL/sim/simHelper.h
-    target/SITL/sim/simple_soap_client.c
-    target/SITL/sim/simple_soap_client.h
-    target/SITL/sim/xplane.c
-    target/SITL/sim/xplane.h
+    drivers/serial_websocket.c
+    drivers/serial_websocket.h
 )
 
+# Only include TCP server and simulator code for non-WASM builds
+if(NOT ${TOOLCHAIN} STREQUAL "wasm")
+    # File-based config storage for native SITL
+    main_sources(SITL_SRC
+        config/config_streamer_file.c
+    )
+    main_sources(SITL_SRC
+        drivers/serial_tcp.c
+        drivers/serial_tcp.h
+        target/SITL/sim/realFlight.c
+        target/SITL/sim/realFlight.h
+        target/SITL/sim/simHelper.c
+        target/SITL/sim/simHelper.h
+        target/SITL/sim/simple_soap_client.c
+        target/SITL/sim/simple_soap_client.h
+        target/SITL/sim/xplane.c
+        target/SITL/sim/xplane.h
+    )
+else()
+    # WASM-specific: Manual PG registry (linker script not supported)
+    # RAM-based config storage (no file I/O in browser)
+    main_sources(SITL_SRC
+        config/config_streamer_ram.c
+        target/SITL/wasm_pg_registry.c
+        target/SITL/wasm_pg_runtime.c
+        target/SITL/wasm_pg_runtime.h
+        target/SITL/wasm_stubs.c
+        target/SITL/wasm_msp_bridge.c
+        target/SITL/wasm_eeprom_bridge.c
+        target/SITL/wasm_eeprom_bridge.h
+        target/SITL/serial_wasm.c
+        target/SITL/serial_wasm.h
+    )
+endif()
+
 
 if(CMAKE_HOST_APPLE)
   set(MACOSX ON)
@@ -38,14 +64,14 @@ if(${CYGWIN})
     set(SITL_LINK_OPTIONS ${SITL_LINK_OPTIONS} "-static-libgcc")
 endif()
 
-set(SITL_LINK_LIBRARIS
+set(SITL_LINK_LIBRARIES
     -lpthread
     -lm
     -lc
 )
 
 if(NOT MACOSX)
-    set(SITL_LINK_LIBRARIS ${SITL_LINK_LIBRARIS} -lrt)
+    set(SITL_LINK_LIBRARIES ${SITL_LINK_LIBRARIES} -lrt)
 endif()
 
 set(SITL_COMPILE_OPTIONS
@@ -64,9 +90,10 @@ if(NOT MACOSX)
         -Wno-error=maybe-uninitialized
         -fsingle-precision-constant
     )
-    if (CMAKE_COMPILER_IS_GNUCC AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.0)
-        set(SITL_LINK_OPTIONS ${SITL_LINK_OPTIONS} "-Wl,--no-warn-rwx-segments")
-    endif()
+    # Temporarily disabled - ld version may not support this flag
+    # if (CMAKE_COMPILER_IS_GNUCC AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.0)
+    #     set(SITL_LINK_OPTIONS ${SITL_LINK_OPTIONS} "-Wl,--no-warn-rwx-segments")
+    # endif()
 else()
     set(SITL_COMPILE_OPTIONS ${SITL_COMPILE_OPTIONS}
     )
@@ -76,12 +103,51 @@ set(SITL_DEFINITIONS
     SITL_BUILD
 )
 
+# WebAssembly-specific settings
+if(${TOOLCHAIN} STREQUAL "wasm")
+    # Disable simulator for WASM builds
+    list(APPEND SITL_DEFINITIONS SKIP_SIMULATOR=1)
+    # Use RAM-based config storage (no file I/O in browser)
+    list(APPEND SITL_DEFINITIONS CONFIG_IN_RAM)
+
+    # Emscripten-specific compile options
+    set(SITL_COMPILE_OPTIONS ${SITL_COMPILE_OPTIONS}
+        # Phase 5 MVP: Disable pthreads
+        # -pthread
+        -funsigned-char
+        -g                          # Debug symbols for browser DevTools
+    )
+
+    # Emscripten linker options
+    set(SITL_LINK_OPTIONS
+        # Phase 5 MVP: Disable pthreads to avoid COOP/COEP header requirements
+        # -pthread
+        # -sUSE_PTHREADS=1
+        # -sPTHREAD_POOL_SIZE=8
+        -sALLOW_MEMORY_GROWTH=1
+        # ASYNCIFY allows WASM to unwind the call stack when exiting from EM_ASM callbacks.
+        # Without this, emscripten_force_exit() called from within EM_ASM (in systemReset)
+        # would freeze the JS event loop, preventing the reload IPC message from being processed.
+        -sASYNCIFY=1
+        -sWEBSOCKET_URL="ws://localhost:5771"
+        -sFORCE_FILESYSTEM=1
+        -sEXPORTED_FUNCTIONS=_main,_serialWriteByte,_serialReadByte,_serialAvailable,_serialGetRxDroppedBytes,_serialGetTxDroppedBytes,_wasmGetEepromPtr,_wasmGetEepromSize,_wasmReloadConfig,_wasmIsEepromValid,_malloc,_free
+        -sEXPORTED_RUNTIME_METHODS=ccall,cwrap,UTF8ToString,stringToUTF8,lengthBytesUTF8,getValue,setValue,HEAPU8,callMain
+        -gsource-map                                      # Generate .wasm.map for browser debugging
+        -lidbfs.js
+    )
+
+    # Override libraries for WASM (no system libs needed)
+    set(SITL_LINK_LIBRARIES "")
+endif()
+
 function (target_sitl name)
     if(CMAKE_VERSION VERSION_GREATER 3.22)
         set(CMAKE_C_STANDARD 17)
     endif()
 
-    if(NOT host STREQUAL TOOLCHAIN)
+    # Accept both host and wasm toolchains for SITL builds
+    if(NOT ${TOOLCHAIN} STREQUAL "host" AND NOT ${TOOLCHAIN} STREQUAL "wasm")
         return()
     endif()
 
@@ -123,16 +189,19 @@ function (target_sitl name)
 
     target_compile_options(${exe_target} PRIVATE ${SITL_COMPILE_OPTIONS})
 
-    target_link_libraries(${exe_target} PRIVATE ${SITL_LINK_LIBRARIS})
+    target_link_libraries(${exe_target} PRIVATE ${SITL_LINK_LIBRARIES})
     target_link_options(${exe_target} PRIVATE ${SITL_LINK_OPTIONS})
 
-    set(script_path ${MAIN_SRC_DIR}/target/link/sitl.ld)
-    if(NOT EXISTS ${script_path})
-        message(FATAL_ERROR "linker script ${script_path} doesn't exist")
-    endif()
-    set_target_properties(${exe_target} PROPERTIES LINK_DEPENDS ${script_path})
-    if(NOT MACOSX)
-        target_link_options(${exe_target} PRIVATE -T${script_path})
+    # Only use linker script for non-WASM builds
+    if(NOT ${TOOLCHAIN} STREQUAL "wasm")
+        set(script_path ${MAIN_SRC_DIR}/target/link/sitl.ld)
+        if(NOT EXISTS ${script_path})
+            message(FATAL_ERROR "linker script ${script_path} doesn't exist")
+        endif()
+        set_target_properties(${exe_target} PROPERTIES LINK_DEPENDS ${script_path})
+        if(NOT MACOSX)
+            target_link_options(${exe_target} PRIVATE -T${script_path})
+        endif()
     endif()
 
     if(${CYGWIN})

cmake/wasm-checks.cmake

@@ -0,0 +1,4 @@
+# WASM toolchain checks
+# Emscripten provides its own compiler checks, so this file is minimal
+
+# No additional checks needed for WASM/Emscripten builds

cmake/wasm.cmake

@@ -0,0 +1,46 @@
+# Emscripten/WebAssembly toolchain for SITL
+# This toolchain allows INAV SITL to compile to WebAssembly for browser-based simulation
+
+# Set build type if not specified
+if(NOT CMAKE_CONFIGURATION_TYPES)
+    set(CMAKE_CONFIGURATION_TYPES Debug Release RelWithDebInfo)
+endif()
+if(CMAKE_BUILD_TYPE STREQUAL "")
+    set(CMAKE_BUILD_TYPE RelWithDebInfo)
+endif()
+
+# Find Emscripten
+if(NOT DEFINED ENV{EMSDK})
+    if(EXISTS "$ENV{HOME}/emsdk/emsdk_env.sh")
+        message(STATUS "EMSDK not set, trying to use ~/emsdk")
+        set(ENV{EMSDK} "$ENV{HOME}/emsdk")
+    else()
+        message(FATAL_ERROR "EMSDK environment variable not set. Please run: source ~/emsdk/emsdk_env.sh")
+    endif()
+endif()
+
+# Set Emscripten compilers
+set(CMAKE_SYSTEM_NAME Emscripten)
+set(CMAKE_SYSTEM_VERSION 1)
+
+set(CMAKE_C_COMPILER "emcc" CACHE INTERNAL "c compiler")
+set(CMAKE_CXX_COMPILER "em++" CACHE INTERNAL "c++ compiler")
+set(CMAKE_AR "emar" CACHE INTERNAL "ar")
+set(CMAKE_RANLIB "emranlib" CACHE INTERNAL "ranlib")
+
+# Build type flags
+set(debug_options "-O0 -g")
+set(release_options "-O2 -DNDEBUG")
+set(relwithdebinfo_options "-g ${release_options}")
+
+set(CMAKE_C_FLAGS_DEBUG ${debug_options} CACHE INTERNAL "c compiler flags debug")
+set(CMAKE_CXX_FLAGS_DEBUG ${debug_options} CACHE INTERNAL "c++ compiler flags debug")
+
+set(CMAKE_C_FLAGS_RELEASE ${release_options} CACHE INTERNAL "c compiler flags release")
+set(CMAKE_CXX_FLAGS_RELEASE ${release_options} CACHE INTERNAL "cxx compiler flags release")
+
+set(CMAKE_C_FLAGS_RELWITHDEBINFO ${relwithdebinfo_options} CACHE INTERNAL "c compiler flags relwithdebinfo")
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO ${relwithdebinfo_options} CACHE INTERNAL "cxx compiler flags relwithdebinfo")
+
+# Mark as configured for Emscripten
+set(CMAKE_CROSSCOMPILING_EMULATOR "\${CMAKE_CURRENT_BINARY_DIR}/node_modules/.bin/node" CACHE FILEPATH "Node.js for running WebAssembly")

src/main/config/config_streamer_ram.c

@@ -19,6 +19,11 @@
 #include "platform.h"
 #include "drivers/system.h"
 #include "config/config_streamer.h"
+#include "common/utils.h"
+
+#ifdef __EMSCRIPTEN__
+#include "target/SITL/wasm_eeprom_bridge.h"
+#endif
 
 #if defined(CONFIG_IN_RAM)
 
@@ -32,6 +37,11 @@ void config_streamer_impl_unlock(void)
 void config_streamer_impl_lock(void)
 {
     streamerLocked = true;
+
+#ifdef __EMSCRIPTEN__
+    // Notify JavaScript that EEPROM was saved so it can persist to IndexedDB
+    wasmNotifyEepromSaved();
+#endif
 }
 
 int config_streamer_impl_write_word(config_streamer_t *c, config_streamer_buffer_align_type_t *buffer)

src/main/config/parameter_group.c

@@ -50,13 +50,25 @@ static void pgResetInstance(const pgRegistry_t *reg, uint8_t *base)
     const uint16_t regSize = pgSize(reg);
 
     memset(base, 0, regSize);
+#ifdef __EMSCRIPTEN__
+    // WASM: Can't use linker section boundaries (__pg_resetdata_start/end are stubs)
+    // Heuristic: In WASM, function table indices are small integers (< 4096),
+    // while data pointers are actual memory addresses (>= 4096 in Emscripten's layout).
+    // Reset templates are data; reset functions are function pointers.
+    if (reg->reset.ptr && (uintptr_t)reg->reset.ptr >= 4096) {
+        // Likely a data template pointer - use it
+        memcpy(base, reg->reset.ptr, regSize);
+    }
+    // Skip function pointer calls - they cause "table index out of bounds" in WASM
+#else
     if (reg->reset.ptr >= (void*)__pg_resetdata_start && reg->reset.ptr < (void*)__pg_resetdata_end) {
         // pointer points to resetdata section, to it is data template
         memcpy(base, reg->reset.ptr, regSize);
     } else if (reg->reset.fn) {
         // reset function, call it
         reg->reset.fn(base);
     }
+#endif
 }
 
 void pgReset(const pgRegistry_t* reg, int profileIndex)

src/main/config/parameter_group.h

@@ -61,7 +61,16 @@ static inline uint16_t pgIsProfile(const pgRegistry_t* reg) {return (reg->size &
 
 #define PG_PACKED __attribute__((packed))
 
-#ifdef __APPLE__
+#ifdef __EMSCRIPTEN__
+// WASM builds use manual registry (linker script sections not supported)
+extern const pgRegistry_t* const __pg_registry_start;
+extern const pgRegistry_t* const __pg_registry_end;
+#define PG_REGISTER_ATTRIBUTES __attribute__ ((used, aligned(4)))
+
+extern const uint8_t* const __pg_resetdata_start;
+extern const uint8_t* const __pg_resetdata_end;
+#define PG_RESETDATA_ATTRIBUTES __attribute__ ((used, aligned(2)))
+#elif defined(__APPLE__)
 extern const pgRegistry_t __pg_registry_start[] __asm("section$start$__DATA$__pg_registry");
 extern const pgRegistry_t __pg_registry_end[] __asm("section$end$__DATA$__pg_registry");
 #define PG_REGISTER_ATTRIBUTES __attribute__ ((section("__DATA,__pg_registry"), used, aligned(8)))