AP_Camera: use timer for faster camera trigger pin detection

libraries/AP_Camera/AP_Camera.cpp

@@ -113,6 +113,12 @@ AP_Camera::relay_pic()
 void
 AP_Camera::trigger_pic(bool send_mavlink_msg)
 {
+    if (_feedback_pin > 0 && !_timer_installed) {
+        // install a 1kHz timer to check feedback pin
+        _timer_installed = true;
+        hal.scheduler->register_timer_process(FUNCTOR_BIND_MEMBER(&AP_Camera::feedback_pin_timer, void));
+    }
+
     _image_index++;
     switch (_trigger_type)
     {
@@ -284,3 +290,35 @@ bool AP_Camera::update_location(const struct Location &loc, const AP_AHRS &ahrs)
         return true;
     }
 }
+
+/*
+  check if feedback pin is high
+ */
+void AP_Camera::feedback_pin_timer(void)
+{
+    int8_t dpin = hal.gpio->analogPinToDigitalPin(_feedback_pin);
+    if (dpin == -1) {
+        return;
+    }
+    // ensure we are in input mode
+    hal.gpio->pinMode(dpin, HAL_GPIO_INPUT);
+
+    // enable pullup
+    hal.gpio->write(dpin, 1);
+
+    if (hal.gpio->read(dpin) != 0) {
+        _camera_triggered = true;
+    }
+}
+
+/*
+  check if camera has triggered
+ */
+bool AP_Camera::check_trigger_pin(void)
+{
+    if (_camera_triggered) {
+        _camera_triggered = false;
+        return true;
+    }
+    return false;
+}

libraries/AP_Camera/AP_Camera.h

@@ -45,9 +45,6 @@ public:
     // pin number for accurate camera feedback messages
     AP_Int8         _feedback_pin;
     
-    // this is set to 1 when camera really has been triggered    
-    AP_Int8         _camera_triggered;
-    
     // single entry point to take pictures
     //  set send_mavlink_msg to true to send DO_DIGICAM_CONTROL message to all components
     void            trigger_pic(bool send_mavlink_msg);
@@ -70,6 +67,12 @@ public:
     // Update location of vehicle and return true if a picture should be taken
     bool update_location(const struct Location &loc, const AP_AHRS &ahrs);
 
+    // check if trigger pin has fired
+    bool check_trigger_pin(void);
+
+    // return true if we are using a feedback pin
+    bool using_feedback_pin(void) const { return _feedback_pin > 0; }
+    
     static const struct AP_Param::GroupInfo        var_info[];
 
 private:
@@ -83,6 +86,7 @@ private:
 
     void            servo_pic();        // Servo operated camera
     void            relay_pic();        // basic relay activation
+    void            feedback_pin_timer();
     
     AP_Float        _trigg_dist;        // distance between trigger points (meters)
     AP_Int16        _min_interval;      // Minimum time between shots required by camera
@@ -91,6 +95,9 @@ private:
     struct Location _last_location;
     uint16_t        _image_index;       // number of pictures taken since boot
 
+    // this is set to 1 when camera trigger pin has fired
+    volatile bool   _camera_triggered;
+    bool            _timer_installed:1;
 };
 
 #endif /* AP_CAMERA_H */