Added explicit locks around all sequences of commands.

MeadeAutostar497/Controller/TelescopeController.cs

@@ -561,6 +561,9 @@ namespace ASCOM.MeadeAutostar497.Controller
                 Thread.Sleep(duration); //todo figure out if this is really needed
             }
             else
+            {
+                SerialPort.Lock();
+                try
                 {
                     _serialPort.Command(":RG#"); //Make sure we are at guide rate
                     _serialPort.Command($":M{d}#");
@@ -571,6 +574,11 @@ namespace ASCOM.MeadeAutostar497.Controller
                     Thread.Sleep(200);
                     _serialPort.Command($":Q{d}#");
                 }
+                finally
+                {
+                    SerialPort.Unlock();
+                }
+            }
         }
 
         public void Park()
@@ -593,12 +601,20 @@ namespace ASCOM.MeadeAutostar497.Controller
         }
 
         public void SlewToCoordinatesAsync(double rightAscension, double declination)
+        {
+            SerialPort.Lock();
+            try
             {
                 TargetRightAscension = rightAscension;
                 TargetDeclination = declination;
 
                 DoSlewAsync(true);
             }
+            finally
+            {
+                SerialPort.Unlock();
+            }
+        }
 
         public void SlewToAltAz(double azimuth, double altitude)
         {
@@ -662,12 +678,20 @@ namespace ASCOM.MeadeAutostar497.Controller
         }
 
         public void SlewToAltAzAsync(double azimuth, double altitude)
+        {
+            SerialPort.Lock();
+            try
             {
                 TargetAltitude = altitude;
                 TargetAzimuth = azimuth;
 
                 DoSlewAsync(false);
             }
+            finally
+            {
+                SerialPort.Unlock();
+            }
+        }
 
         public void SyncToTarget()
         {
@@ -707,10 +731,13 @@ namespace ASCOM.MeadeAutostar497.Controller
         private bool _movingPrimary;
         private bool _movingSecondary;
         public void MoveAxis(TelescopeAxes axis, double rate)
+        {
+            SerialPort.Lock();
+            try
             {
                 var absrate = Math.Abs(rate);
 
-            switch(absrate)
+                switch (absrate)
                 {
                     case 0:
                         //do nothing, it's ok this time as we're halting the slew.
@@ -767,6 +794,7 @@ namespace ASCOM.MeadeAutostar497.Controller
                             //Returns: Nothing
                             _movingPrimary = true;
                         }
+
                         break;
                     case TelescopeAxes.axisSecondary:
                         if (rate == 0)
@@ -799,6 +827,11 @@ namespace ASCOM.MeadeAutostar497.Controller
                         throw new ASCOM.MethodNotImplementedException("Can not move this axis.");
                 }
             }
+            finally
+            {
+                SerialPort.Unlock();
+            }
+        }
 
         public void FocuserHalt()
         {
@@ -809,6 +842,9 @@ namespace ASCOM.MeadeAutostar497.Controller
 
         //todo remove the polar parameter and split method into two.
         private void DoSlewAsync( bool polar) 
+        {
+            SerialPort.Lock();
+            try
             {
                 switch (polar)
                 {
@@ -837,6 +873,7 @@ namespace ASCOM.MeadeAutostar497.Controller
                                 throw new ASCOM.DriverException("This error should not happen");
 
                         }
+
                         break;
                     case false:
                         var maResponse = SerialPort.CommandChar(":MA#");
@@ -850,9 +887,15 @@ namespace ASCOM.MeadeAutostar497.Controller
                         {
                             throw new ASCOM.InvalidOperationException("fault");
                         }
+
                         break;
                 }
             }
+            finally
+            {
+                SerialPort.Unlock();
+            }
+        }
 
         public bool UserNewerPulseGuiding { get; set; } = true; //todo make this a device setting
     }