feat: built-in AVR ATmega2560 simulator

package.json

@@ -55,6 +55,7 @@
     "@tanstack/react-table": "^8.10.7",
     "@xyflow/react": "^12.0.1",
     "auto-zustand-selectors-hook": "^2.0.0",
+    "avr8js": "0.20.0",
     "clsx": "^2.0.0",
     "cva": "npm:class-variance-authority@^0.7.0",
     "dompurify": "^3.2.4",

resources/sources/Baremetal/Baremetal.ino

@@ -339,4 +339,12 @@ void loop()
         modbusTask();
     }
     #endif
+
+    #ifdef SIMULATOR_MODE
+    // In the emulated ATmega2560, busy-waiting wastes host CPU executing
+    // millions of useless instructions. SLEEP (opcode 0x9588) is detected
+    // by the emulator which fast-forwards the clock to the next timer event
+    // instead of stepping through every idle cycle.
+    __asm volatile("sleep");
+    #endif
 }

resources/sources/boards/hals.json

@@ -1,4 +1,29 @@
 {
+  "OpenPLC Simulator": {
+    "compiler": "simulator",
+    "core": "arduino:avr",
+    "c_flags": ["-MMD", "-c", "-Wno-incompatible-pointer-types"],
+    "ld_flags": ["-Wl,--defsym,__DATA_REGION_LENGTH__=0xFE00", "-Wl,--defsym,__stack=0x80FFFF"],
+    "default_ain": "A0, A1, A2, A3, A4, A5, A6, A7",
+    "default_aout": "2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13",
+    "default_din": "62, 63, 64, 65, 66, 67, 68, 69, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52",
+    "default_dout": "14, 15, 16, 17, 18, 19, 20, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53",
+    "extra_libraries": [],
+    "platform": "arduino:avr:mega",
+    "source": "mega_due.cpp",
+    "preview": "simulator.png",
+    "specs": {
+      "CPU": "Emulated ATmega2560 at 16MHz",
+      "RAM": "63.5 KB",
+      "Flash": "256 KB",
+      "Digital Pins": "70",
+      "Analog Pins": "16",
+      "PWM Pins": "15",
+      "WiFi": "No",
+      "Bluetooth": "No",
+      "Ethernet": "No"
+    }
+  },
   "Arduino Due (native USB port)": {
     "compiler": "arduino-cli",
     "core": "arduino:sam",

src/main/modules/compiler/compiler-module.ts

@@ -687,11 +687,13 @@ class CompilerModule {
     projectPath,
     buildMD5Hash,
     boardTarget,
+    boardRuntime,
     _handleOutputData,
   }: {
     projectPath: string
     boardTarget: string
     buildMD5Hash: string
+    boardRuntime: string
     _handleOutputData: HandleOutputDataCallback
   }) {
     let DEFINES_CONTENT: string = ''
@@ -753,10 +755,19 @@ class CompilerModule {
 
     // 3.2. Device Configuration
     DEFINES_CONTENT += '//Comms Configuration\n'
-    DEFINES_CONTENT += `#define MBSERIAL_IFACE ${modbusRTU.rtuInterface}\n`
-    DEFINES_CONTENT += `#define MBSERIAL_BAUD ${modbusRTU.rtuBaudRate}\n`
-    if (modbusRTU.rtuSlaveId !== null) DEFINES_CONTENT += `#define MBSERIAL_SLAVE ${modbusRTU.rtuSlaveId}\n`
-    if (modbusRTU.rtuRS485ENPin !== null) DEFINES_CONTENT += `#define MBSERIAL_TXPIN ${modbusRTU.rtuRS485ENPin}\n`
+    if (boardRuntime === 'simulator') {
+      // Simulator forces fixed Modbus RTU settings over emulated USART0.
+      // On ATmega2560, Serial = USART0. avr8js bridges usart0.
+      DEFINES_CONTENT += '#define SIMULATOR_MODE\n'
+      DEFINES_CONTENT += '#define MBSERIAL_IFACE Serial\n'
+      DEFINES_CONTENT += '#define MBSERIAL_BAUD 115200\n'
+      DEFINES_CONTENT += '#define MBSERIAL_SLAVE 1\n'
+    } else {
+      DEFINES_CONTENT += `#define MBSERIAL_IFACE ${modbusRTU.rtuInterface}\n`
+      DEFINES_CONTENT += `#define MBSERIAL_BAUD ${modbusRTU.rtuBaudRate}\n`
+      if (modbusRTU.rtuSlaveId !== null) DEFINES_CONTENT += `#define MBSERIAL_SLAVE ${modbusRTU.rtuSlaveId}\n`
+      if (modbusRTU.rtuRS485ENPin !== null) DEFINES_CONTENT += `#define MBSERIAL_TXPIN ${modbusRTU.rtuRS485ENPin}\n`
+    }
     if (modbusTCP.tcpMacAddress !== null)
       DEFINES_CONTENT += `#define MBTCP_MAC ${FormatMacAddress(modbusTCP.tcpMacAddress)}\n`
     // OBS: This is giving us an empty string and this is being printed as a space
@@ -769,7 +780,7 @@ class CompilerModule {
     if (modbusTCP.tcpStaticHostConfiguration.subnet !== null)
       DEFINES_CONTENT += `#define MBTCP_SUBNET ${modbusTCP.tcpStaticHostConfiguration.subnet.replaceAll('.', ',')}\n`
 
-    if (communicationPreferences.enabledRTU) {
+    if (communicationPreferences.enabledRTU || boardRuntime === 'simulator') {
       DEFINES_CONTENT += '#define MBSERIAL\n'
       DEFINES_CONTENT += '#define MODBUS_ENABLED\n'
     }
@@ -1004,6 +1015,14 @@ class CompilerModule {
       ]
     }
 
+    if (boardHalsContent['ld_flags']) {
+      buildProjectFlags = [
+        ...buildProjectFlags,
+        '--build-property',
+        `compiler.c.elf.extra_flags=${boardHalsContent['ld_flags'].map((f: string) => f).join(' ')}`,
+      ]
+    }
+
     buildProjectFlags = [
       ...buildProjectFlags,
       '--library',
@@ -2019,6 +2038,7 @@ class CompilerModule {
         projectPath: normalizedProjectPath,
         boardTarget,
         buildMD5Hash,
+        boardRuntime,
         _handleOutputData: (data, logLevel) => {
           _mainProcessPort.postMessage({ logLevel, message: data })
         },
@@ -2065,7 +2085,25 @@ class CompilerModule {
       return
     }
 
-    // Step 13: Upload program to board if necessary
+    // Step 13: Upload program to board or load into simulator
+    if (boardRuntime === 'simulator') {
+      // For simulator targets, send the HEX firmware path back to the renderer.
+      // Derive the build sub-directory from the platform FQBN (e.g. "arduino:avr:mega" → "arduino.avr.mega")
+      // so it stays in sync with the hals.json entry.
+      const fqbnSubDir = halsContent[boardTarget]['platform'].replaceAll(':', '.')
+      const hexPath = join(compilationPath, 'examples', 'Baremetal', 'build', fqbnSubDir, 'Baremetal.ino.hex')
+      _mainProcessPort.postMessage({
+        logLevel: 'info',
+        message: 'Compilation successful. Loading firmware into simulator...',
+      })
+      _mainProcessPort.postMessage({
+        simulatorFirmwarePath: hexPath,
+        closePort: true,
+      })
+      _mainProcessPort.close()
+      return
+    }
+
     if (!compileOnly) {
       _mainProcessPort.postMessage({ logLevel: 'info', message: 'Uploading program to board...' })
       try {

src/main/modules/compiler/compiler-types.ts

@@ -16,7 +16,7 @@ const ArduinoCoreControlSchema = z.array(z.record(z.string(), z.string()))
 type ArduinoCoreControl = z.infer<typeof ArduinoCoreControlSchema>
 
 const BoardInfoSchema = z.object({
-  compiler: z.enum(['arduino-cli', 'openplc-compiler']),
+  compiler: z.enum(['arduino-cli', 'openplc-compiler', 'simulator']),
   core: z.string(),
   default_ain: z.string(),
   default_aout: z.string(),
@@ -35,6 +35,7 @@ const BoardInfoSchema = z.object({
   user_dout: z.string().optional(),
   c_flags: z.array(z.string()).optional(),
   cxx_flags: z.array(z.string()).optional(),
+  ld_flags: z.array(z.string()).optional(),
   arch: z.string().optional(),
 })
 

src/main/modules/hardware/hardware-module.ts

@@ -182,11 +182,9 @@ class HardwareModule {
         })
       })
     }
-    // TODO: Improve error handling and return type
-    // if (availableBoards.size === 0) {
-    //   return { success: false, data: undefined }
-    // }
-    return availableBoards
+    // Sort boards alphabetically by name
+    const sortedBoards: AvailableBoards = new Map([...availableBoards.entries()].sort(([a], [b]) => a.localeCompare(b)))
+    return sortedBoards
   }
 
   async getBoardImagePreview(image: string) {

src/main/modules/hardware/hardware-types.ts

@@ -13,6 +13,7 @@ const BoardInfoSchema = z.object({
   core: z.string(),
   c_flags: z.array(z.string()).optional(),
   cxx_flags: z.array(z.string()).optional(),
+  ld_flags: z.array(z.string()).optional(),
   default_ain: z.string(),
   default_aout: z.string(),
   default_din: z.string(),