GCS_MAVLink: added method to lockup autopilot

used for watchdog testing

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -2537,6 +2537,19 @@ void GCS_MAVLINK::zero_rc_outputs()
  */
 MAV_RESULT GCS_MAVLINK::handle_preflight_reboot(const mavlink_command_long_t &packet)
 {
+    if (is_equal(packet.param1, 42.0f) &&
+        is_equal(packet.param2, 24.0f) &&
+        is_equal(packet.param3, 71.0f) &&
+        is_equal(packet.param4, 93.0f)) {
+        // this is a magic sequence to force the main loop to
+        // lockup. This is for testing the stm32 watchdog
+        // functionality
+        while (true) {
+            send_text(MAV_SEVERITY_WARNING,"entering lockup");
+            hal.scheduler->delay(250);
+        }
+    }
+
     if (hal.util->get_soft_armed()) {
         // refuse reboot when armed
         return MAV_RESULT_FAILED;