feat: update PWM handling in SimulatorCanvas and enhance I2C Scanner example with SSD1306 OLED integration

frontend/src/components/simulator/SimulatorCanvas.tsx

@@ -463,10 +463,12 @@ export const SimulatorCanvas = () => {
       );
       unsubscribers.push(unsubscribe);
 
-      // PWM subscription: update LED opacity when the pin receives a LEDC duty cycle
+      // PWM subscription: update LED opacity when the pin receives a LEDC duty cycle.
+      // duty=0 means no PWM / analogWrite(0) — clear the inline style so the
+      // component keeps its default visibility instead of becoming invisible.
       const pwmUnsub = pinManager.onPwmChange(pin, (_p, duty) => {
         const el = document.getElementById(component.id);
-        if (el) el.style.opacity = String(duty);  // duty is 0.0–1.0
+        if (el) el.style.opacity = duty > 0 ? String(duty) : '';
       });
       unsubscribers.push(pwmUnsub);
     };

frontend/src/data/examples.ts

@@ -932,7 +932,7 @@ void loop() {
   {
     id: 'i2c-scanner',
     title: 'I2C Scanner (TWI)',
-    description: 'Scans the I2C bus and reports all devices found. Tests TWI protocol. Virtual devices at 0x48, 0x50, 0x68 should be detected.',
+    description: 'Scans the I2C bus and reports all devices found. SSD1306 OLED (0x3C) is wired on canvas; virtual devices at 0x48, 0x50, 0x68 also respond.',
     category: 'communication',
     difficulty: 'intermediate',
     code: `// I2C Bus Scanner — TWI Protocol Test
@@ -999,8 +999,14 @@ void loop() {
 `,
     components: [
       { type: 'wokwi-arduino-uno', id: 'arduino-uno', x: 100, y: 100, properties: {} },
+      { type: 'wokwi-ssd1306', id: 'ssd1306-1', x: 420, y: 120, properties: {} },
+    ],
+    wires: [
+      { id: 'wire-sda',  start: { componentId: 'arduino-uno', pinName: 'A4' },   end: { componentId: 'ssd1306-1', pinName: 'DATA' }, color: '#2196f3' },
+      { id: 'wire-scl',  start: { componentId: 'arduino-uno', pinName: 'A5' },   end: { componentId: 'ssd1306-1', pinName: 'CLK'  }, color: '#ff9800' },
+      { id: 'wire-gnd',  start: { componentId: 'arduino-uno', pinName: 'GND.1' }, end: { componentId: 'ssd1306-1', pinName: 'GND'  }, color: '#000000' },
+      { id: 'wire-vcc',  start: { componentId: 'arduino-uno', pinName: '5V' },   end: { componentId: 'ssd1306-1', pinName: 'VIN'  }, color: '#ff0000' },
     ],
-    wires: [],
   },
   {
     id: 'i2c-rtc-read',

frontend/src/simulation/AVRSimulator.ts

@@ -255,7 +255,7 @@ export class AVRSimulator {
     this.lastPortBValue = 0;
     this.lastPortCValue = 0;
     this.lastPortDValue = 0;
-    this.lastOcrValues = new Array(this.pwmPins.length).fill(-1);
+    this.lastOcrValues = new Array(this.pwmPins.length).fill(0);
 
     this.setupPinHooks();
 
@@ -503,7 +503,7 @@ export class AVRSimulator {
       this.lastPortBValue = 0;
       this.lastPortCValue = 0;
       this.lastPortDValue = 0;
-      this.lastOcrValues = new Array(this.pwmPins.length).fill(-1);
+      this.lastOcrValues = new Array(this.pwmPins.length).fill(0);
       this.setupPinHooks();
 
       console.log('AVR CPU reset complete');

frontend/src/store/useSimulatorStore.ts

@@ -497,10 +497,10 @@ export const useSimulatorStore = create<SimulatorState>((set, get) => {
 
       set((s) => {
         const boards = s.boards.map((b) =>
-          b.id === boardId ? { ...b, running: true } : b
+          b.id === boardId ? { ...b, running: true, serialMonitorOpen: true } : b
         );
         const isActive = s.activeBoardId === boardId;
-        return { boards, ...(isActive ? { running: true } : {}) };
+        return { boards, ...(isActive ? { running: true, serialMonitorOpen: true } : {}) };
       });
     },