From eaf56766362025045f56ee3f6fa4d4682dfd5df2 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Mon, 9 Jan 2017 09:55:14 +1100
Subject: [PATCH] SITL: fixed unselection bitmask bug in XPlane

---
 libraries/SITL/SIM_XPlane.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libraries/SITL/SIM_XPlane.cpp b/libraries/SITL/SIM_XPlane.cpp
index 09c4c9e341..7729655ffc 100644
--- a/libraries/SITL/SIM_XPlane.cpp
+++ b/libraries/SITL/SIM_XPlane.cpp
@@ -287,8 +287,13 @@ bool XPlane::receive_data(void)
 
     if (data_mask != required_mask) {
         // ask XPlane to change what data it sends
-        select_data(data_mask & ~required_mask, required_mask & ~data_mask);
-        goto failed;
+        uint64_t usel = data_mask & ~required_mask;
+        uint64_t sel = required_mask & ~data_mask;
+        usel &= ~unselected_mask;
+        if (usel || sel) {
+            select_data(usel, sel);
+            goto failed;
+        }
     }
     position = pos + position_zero;
     update_position();