From f95b06a88017f526c11e4bde2180b32294d07811 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Sat, 11 Aug 2012 08:57:32 +1000
Subject: [PATCH] AHRS: make airspeed sensor available to AHRS

this will be used for long term dead-reckoning
---
 libraries/AP_AHRS/AP_AHRS.h         | 7 ++++++-
 libraries/AP_Airspeed/AP_Airspeed.h | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index b7ab34a856..fc75f9e9b0 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -12,6 +12,7 @@
 #include <AP_Math.h>
 #include <inttypes.h>
 #include <AP_Compass.h>
+#include <AP_Airspeed.h>
 #include <AP_GPS.h>
 #include <AP_IMU.h>
 #include <AP_Baro.h>
@@ -46,6 +47,7 @@ public:
 	void		set_fly_forward(bool b) { _fly_forward = b; }
 	void		set_compass(Compass *compass) { _compass = compass; }
 	void		set_barometer(AP_Baro *barometer) { _barometer = barometer; }
+	void		set_airspeed(AP_Airspeed *airspeed) { _airspeed = airspeed; }
 
 	// Methods
 	virtual void update(void) = 0;
@@ -90,9 +92,12 @@ public:
 	//static const struct AP_Param::GroupInfo var_info[];
 
 protected:
-	// pointer to compass object, if enabled
+	// pointer to compass object, if available
 	Compass 	* _compass;
 
+	// pointer to airspeed object, if available
+	AP_Airspeed     * _airspeed;
+
 	// time in microseconds of last compass update
 	uint32_t        _compass_last_update;
 
diff --git a/libraries/AP_Airspeed/AP_Airspeed.h b/libraries/AP_Airspeed/AP_Airspeed.h
index 75628a216a..350dc6954d 100644
--- a/libraries/AP_Airspeed/AP_Airspeed.h
+++ b/libraries/AP_Airspeed/AP_Airspeed.h
@@ -32,7 +32,7 @@ public:
 	float get_airspeed_cm(void) { return _airspeed*100; }
 
     // return true if airspeed is enabled, and airspeed use is set
-    bool use(void) { return _enable && _use; }
+    bool use(void) { return _enable && _use && _offset != 0; }
 
     // return true if airspeed is enabled
     bool enabled(void) { return _enable; }