PlanManager: use shorter timeout to download items

When downloading mission items from the autopilot we need to retry more
agressively, so use a shorter timeout. If we don't do this, we might not
re-request a mission item in time and the autopilot has already given up
the overall mission transfer.

This fixes the case where a mission request from QGC to autopilot or a
mission item from autopilot to QGC gets lost on the link and needs to be
requested again.

src/MissionManager/PlanManager.cc

@@ -36,8 +36,7 @@ PlanManager::PlanManager(Vehicle* vehicle, MAV_MISSION_TYPE planType)
 {
     _ackTimeoutTimer = new QTimer(this);
     _ackTimeoutTimer->setSingleShot(true);
-    _ackTimeoutTimer->setInterval(_ackTimeoutMilliseconds);
-    
+
     connect(_ackTimeoutTimer, &QTimer::timeout, this, &PlanManager::_ackTimeout);
 }
 
@@ -245,6 +244,24 @@ void PlanManager::_ackTimeout(void)
 
 void PlanManager::_startAckTimeout(AckType_t ack)
 {
+    switch (ack) {
+    case AckMissionItem:
+        // We are actively trying to get the mission item, so we don't want to wait as long.
+        _ackTimeoutTimer->setInterval(_retryTimeoutMilliseconds);
+        break;
+    case AckNone:
+        // FALLTHROUGH
+    case AckMissionCount:
+        // FALLTHROUGH
+    case AckMissionRequest:
+        // FALLTHROUGH
+    case AckMissionClearAll:
+        // FALLTHROUGH
+    case AckGuidedItem:
+        _ackTimeoutTimer->setInterval(_ackTimeoutMilliseconds);
+        break;
+    }
+
     _expectedAck = ack;
     _ackTimeoutTimer->start();
 }

src/MissionManager/PlanManager.h

@@ -28,11 +28,11 @@ Q_DECLARE_LOGGING_CATEGORY(PlanManagerLog)
 class PlanManager : public QObject
 {
     Q_OBJECT
-    
+
 public:
     PlanManager(Vehicle* vehicle, MAV_MISSION_TYPE planType);
     ~PlanManager();
-    
+
     bool inProgress(void) const;
     const QList<MissionItem*>& missionItems(void) { return _missionItems; }
 
@@ -41,11 +41,11 @@ public:
 
     /// Last current mission item reported while in Mission flight mode
     int lastCurrentIndex(void) const { return _lastCurrentIndex; }
-    
+
     /// Load the mission items from the vehicle
     ///     Signals newMissionItemsAvailable when done
     void loadFromVehicle(void);
-    
+
     /// Writes the specified set of mission items to the vehicle
     /// IMPORTANT NOTE: PlanManager will take control of the MissionItem objects with the missionItems list. It will free them when done.
     ///     @param missionItems Items to send to vehicle
@@ -70,9 +70,12 @@ public:
     } ErrorCode_t;
 
     // These values are public so the unit test can set appropriate signal wait times
+    // When passively waiting for a mission process, use a longer timeout.
     static const int _ackTimeoutMilliseconds = 1000;
+    // When actively retrying to request mission items, use a shorter timeout instead.
+    static const int _retryTimeoutMilliseconds = 250;
     static const int _maxRetryCount = 5;
-    
+
 signals:
     void newMissionItemsAvailable   (bool removeAllRequested);
     void inProgressChanged          (bool inProgress);
@@ -88,7 +91,7 @@ signals:
 private slots:
     void _mavlinkMessageReceived(const mavlink_message_t& message);
     void _ackTimeout(void);
-    
+
 protected:
     typedef enum {
         AckNone,            ///< State machine is idle
@@ -134,18 +137,18 @@ protected:
     Vehicle*            _vehicle;
     MAV_MISSION_TYPE    _planType;
     LinkInterface*      _dedicatedLink;
-    
+
     QTimer*             _ackTimeoutTimer;
     AckType_t           _expectedAck;
     int                 _retryCount;
-    
+
     TransactionType_t   _transactionInProgress;
     bool                _resumeMission;
     QList<int>          _itemIndicesToWrite;    ///< List of mission items which still need to be written to vehicle
     QList<int>          _itemIndicesToRead;     ///< List of mission items which still need to be requested from vehicle
     int                 _lastMissionRequest;    ///< Index of item last requested by MISSION_REQUEST
     int                 _missionItemCountToRead;///< Count of all mission items to read
-    
+
     QList<MissionItem*> _missionItems;          ///< Set of mission items on vehicle
     QList<MissionItem*> _writeMissionItems;     ///< Set of mission items currently being written to vehicle
     int                 _currentMissionIndex;