From d7faeada8713a2e4902f0d6a755af6ebf3417e4b Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Fri, 22 Jul 2016 12:23:00 +1000
Subject: [PATCH] HAL_SITL: notify GCS on GPIO changes

useful for testing relays in SITL
---
 libraries/AP_HAL_SITL/GPIO.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libraries/AP_HAL_SITL/GPIO.cpp b/libraries/AP_HAL_SITL/GPIO.cpp
index f628648d86..ff54ceb350 100644
--- a/libraries/AP_HAL_SITL/GPIO.cpp
+++ b/libraries/AP_HAL_SITL/GPIO.cpp
@@ -32,12 +32,15 @@ void GPIO::write(uint8_t pin, uint8_t value)
         return;
     }
     uint8_t mask = sitlState->_sitl->pin_mask.get();
+    uint8_t new_mask = mask;
     if (value) {
-        mask |= (1U<<pin);
+        new_mask |= (1U<<pin);
     } else {
-        mask &= ~(1U<<pin);
+        new_mask &= ~(1U<<pin);
+    }
+    if (mask != new_mask) {
+        sitlState->_sitl->pin_mask.set_and_notify(new_mask);
     }
-    sitlState->_sitl->pin_mask.set(mask);
 }
 
 void GPIO::toggle(uint8_t pin)