feat: add simple stall detection with threshold + debounce

- Add STALL_THRESHOLD (8A) and STALL_CONFIRM_SAMPLES (3) config
- Add 500ms stabilization delay after direction change to prevent false positives
- Add stall warning banner in web UI
- Stop motor and pingpong when stall detected

Algorithm: If active current > 8A for 3 consecutive samples (300ms),
and motor has been running for at least 500ms, trigger stall callback.

include/config.h

@@ -40,6 +40,12 @@
 // Current logging interval for data collection
 #define CURRENT_LOG_INTERVAL_MS 100  // Log current readings every 100ms
 
+// Simple Stall Detection
+// Based on clean data: Running ~2A, Stall ~17A (8.5x difference)
+#define STALL_THRESHOLD 8.0f          // Amps - midpoint between 2A run and 17A stall
+#define STALL_CONFIRM_SAMPLES 3       // Debounce: 3 samples = 300ms at 100ms interval
+#define STALL_STABILIZE_MS 500        // Ignore current spikes for 500ms after direction change
+
 // Web Server
 #define HTTP_PORT 80
 

include/motor.h

@@ -4,6 +4,9 @@
 #include <Arduino.h>
 #include "config.h"
 
+// Stall callback function type
+typedef void (*StallCallback)();
+
 class MotorController {
 public:
     void begin();
@@ -18,6 +21,11 @@ public:
     float getCurrentLeft();          // Current in amps (reverse direction)
     float getCurrentActive();        // Current from active direction
     
+    // Stall detection
+    bool isStalled();
+    void setStallCallback(StallCallback callback);
+    void resetStallDetection();
+    
     // Pingpong mode (time-based only)
     void startPingpong(int speed, int timeMs, int speedRandomPercent, int timeRandomPercent);
     void stopPingpong();
@@ -48,11 +56,18 @@ private:
     unsigned long _pingpongLastSwitch = 0;
     int _pingpongDirection = 1;
     
+    // Stall detection state
+    bool _stalled = false;
+    int _stallConfirmCount = 0;
+    StallCallback _stallCallback = nullptr;
+    unsigned long _lastDirectionChangeTime = 0;
+    
     void applyMotorState();
     float readCurrentSense(int pin);
     void calibrateCurrentOffset();
     void updatePingpong();
     int applyRandomness(int baseValue, int randomPercent);
+    void checkStall();
 };
 
 extern MotorController motor;

src/main.cpp

@@ -4,6 +4,13 @@
 #include "motor.h"
 #include "webserver.h"
 
+// Called when motor stall is detected
+void onMotorStall() {
+    Serial.println("Stall callback triggered - stopping motor!");
+    motor.stop();
+    motor.stopPingpong();
+}
+
 void setupWiFi() {
     Serial.println("Connecting to WiFi...");
     
@@ -39,11 +46,12 @@ void setup() {
     
     Serial.println("\n=============================");
     Serial.println("  BTS7960 Motor Controller");
-    Serial.println("  (Stall Detection Removed)");
+    Serial.println("  Simple Stall Detection");
     Serial.println("=============================\n");
     
     // Initialize motor controller
     motor.begin();
+    motor.setStallCallback(onMotorStall);
     
     // Connect to WiFi
     setupWiFi();

src/motor.cpp

@@ -49,7 +49,12 @@ void MotorController::setSpeed(int speed) {
 }
 
 void MotorController::setDirection(int dir) {
-    _direction = constrain(dir, -1, 1);
+    int newDir = constrain(dir, -1, 1);
+    if (newDir != _direction) {
+        _lastDirectionChangeTime = millis();
+        resetStallDetection();
+    }
+    _direction = newDir;
     applyMotorState();
 }
 
@@ -58,6 +63,7 @@ void MotorController::stop() {
     _direction = 0;
     ledcWrite(PWM_CHANNEL_R, 0);
     ledcWrite(PWM_CHANNEL_L, 0);
+    resetStallDetection();
     Serial.println("Motor: STOPPED (manual)");
 }
 
@@ -76,6 +82,9 @@ void MotorController::update() {
         Serial.printf("CURRENT: R=%.2fA L=%.2fA dir=%d spd=%d\n",
                       _currentRight, _currentLeft, _direction, _speed);
     }
+    
+    // Check for stall condition
+    checkStall();
 #endif
     
     // Update pingpong mode
@@ -107,6 +116,61 @@ float MotorController::getCurrentActive() {
     return 0.0f;
 }
 
+// Stall detection
+bool MotorController::isStalled() {
+    return _stalled;
+}
+
+void MotorController::setStallCallback(StallCallback callback) {
+    _stallCallback = callback;
+}
+
+void MotorController::resetStallDetection() {
+    _stalled = false;
+    _stallConfirmCount = 0;
+}
+
+void MotorController::checkStall() {
+    // Only check when motor is running
+    if (_direction == 0 || _speed == 0) {
+        resetStallDetection();
+        return;
+    }
+    
+    // Skip stall check during stabilization period after direction change
+    // (prevents false positives from inrush current spikes)
+    if ((millis() - _lastDirectionChangeTime) < STALL_STABILIZE_MS) {
+        return;
+    }
+    
+    float activeCurrent = getCurrentActive();
+    
+    // Simple threshold-based stall detection with debounce
+    if (activeCurrent > STALL_THRESHOLD) {
+        _stallConfirmCount++;
+        
+        if (_stallConfirmCount >= STALL_CONFIRM_SAMPLES && !_stalled) {
+            _stalled = true;
+            Serial.printf("STALL DETECTED! Current=%.2fA (threshold=%.1fA)\n",
+                          activeCurrent, STALL_THRESHOLD);
+            
+            // Call stall callback if registered
+            if (_stallCallback != nullptr) {
+                _stallCallback();
+            }
+        }
+    } else {
+        // Reset counter if current drops below threshold
+        _stallConfirmCount = 0;
+        
+        // Clear stall flag if current returns to normal
+        if (_stalled) {
+            _stalled = false;
+            Serial.println("Stall condition cleared");
+        }
+    }
+}
+
 void MotorController::applyMotorState() {
     // Apply minimum PWM when motor is running
     int effectiveSpeed = _speed;

src/webserver.cpp

@@ -109,6 +109,19 @@ const char index_html[] PROGMEM = R"rawliteral(
             border-top: 2px solid #0f3460;
             margin: 30px 0;
         }
+        .stall-warning {
+            background: #ff5252;
+            color: white;
+            padding: 15px;
+            border-radius: 10px;
+            margin-bottom: 20px;
+            font-weight: bold;
+            font-size: 18px;
+            display: none;
+        }
+        .stall-warning.active {
+            display: block;
+        }
         .pingpong-section {
             background: #16213e;
             padding: 20px;
@@ -169,6 +182,8 @@ const char index_html[] PROGMEM = R"rawliteral(
     <div class="container">
         <h1>Motor Control</h1>
         
+        <div class="stall-warning" id="stallWarning">⚠️ STALL DETECTED!</div>
+        
         <div class="current-display">
             <div>
                 <div class="current-label">CURRENT R</div>
@@ -323,6 +338,14 @@ const char index_html[] PROGMEM = R"rawliteral(
                     document.getElementById('currentR').textContent = data.currentR.toFixed(2);
                     document.getElementById('currentL').textContent = data.currentL.toFixed(2);
                     
+                    // Update stall warning
+                    const stallWarning = document.getElementById('stallWarning');
+                    if (data.stalled) {
+                        stallWarning.classList.add('active');
+                    } else {
+                        stallWarning.classList.remove('active');
+                    }
+                    
                     // Update pingpong status
                     if (data.pingpong) {
                         ppStatus.textContent = 'ACTIVE';
@@ -387,6 +410,7 @@ void handleStatus() {
                   ",\"direction\":" + String(motor.getDirection()) +
                   ",\"currentR\":" + String(motor.getCurrentRight(), 2) +
                   ",\"currentL\":" + String(motor.getCurrentLeft(), 2) +
+                  ",\"stalled\":" + (motor.isStalled() ? "true" : "false") +
                   ",\"pingpong\":" + (motor.isPingpongActive() ? "true" : "false") +
                   ",\"ppSpeed\":" + String(motor.getPingpongSpeed()) +
                   ",\"ppTime\":" + String(motor.getPingpongTime()) +