MAVLink shell: Fix OS X default path

Tools/mavlink_shell.py

@@ -99,19 +99,22 @@ def main():
 
 
     if args.port == None:
-        serial_list = mavutil.auto_detect_serial(preferred_list=['*FTDI*',
-            "*Arduino_Mega_2560*", "*3D_Robotics*", "*USB_to_UART*", '*PX4*', '*FMU*'])
-
-        if len(serial_list) == 0:
-            print("Error: no serial connection found")
-            return
-
-        if len(serial_list) > 1:
-            print('Auto-detected serial ports are:')
-            for port in serial_list:
-                print(" {:}".format(port))
-        print('Using port {:}'.format(serial_list[0]))
-        args.port = serial_list[0].device
+        if sys.platform == "darwin":
+            args.port = "/dev/tty.usbmodem1"
+        else:
+            serial_list = mavutil.auto_detect_serial(preferred_list=['*FTDI*',
+                "*Arduino_Mega_2560*", "*3D_Robotics*", "*USB_to_UART*", '*PX4*', '*FMU*'])
+
+            if len(serial_list) == 0:
+                print("Error: no serial connection found")
+                return
+
+            if len(serial_list) > 1:
+                print('Auto-detected serial ports are:')
+                for port in serial_list:
+                    print(" {:}".format(port))
+            print('Using port {:}'.format(serial_list[0]))
+            args.port = serial_list[0].device
 
 
     print("Connecting to MAVLINK...")