AP_Baro: added averaging to PX4 baro driver

libraries/AP_Baro/AP_Baro_PX4.cpp

@@ -20,6 +20,7 @@ extern const AP_HAL::HAL& hal;
 // Public Methods //////////////////////////////////////////////////////////////
 bool AP_Baro_PX4::init(void)
 {
+    if (_baro_fd == -1) {
         _baro_fd = open(BARO_DEVICE_PATH, O_RDONLY);
         if (_baro_fd < 0) {
             hal.scheduler->panic("Unable to open " BARO_DEVICE_PATH);
@@ -30,6 +31,8 @@ bool AP_Baro_PX4::init(void)
 
         // average over up to 10 samples
         ioctl(_baro_fd, SENSORIOCSQUEUEDEPTH, 10);
+        hal.console->printf("AP_Baro_PX4: init done fd=%d\n", _baro_fd);
+    }
 
     return true;
 }

libraries/AP_Baro/AP_Baro_PX4.h

@@ -8,6 +8,9 @@
 class AP_Baro_PX4 : public AP_Baro
 {
 public:
+    AP_Baro_PX4() : AP_Baro() {
+        _baro_fd = -1;
+    }
     bool init();
     uint8_t read();
     float get_pressure();