Airspeed: Added AP_Airspeed sensor library

this will allow an airspeed sensor object to be passed to AHRS for
dead reckoning

libraries/AP_Airspeed/AP_Airspeed.cpp

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+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+    APM_Airspeed.cpp - airspeed (pitot) driver
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public License
+    as published by the Free Software Foundation; either version 2.1
+    of the License, or (at your option) any later version.
+*/
+
+#include <FastSerial.h>
+#include <AP_Common.h>
+#include <AP_Airspeed.h>
+#include <LowPassFilter.h>
+
+// table of user settable parameters
+const AP_Param::GroupInfo AP_Airspeed::var_info[] PROGMEM = {
+
+    // @Param: ARSPD_ENABLE
+    // @DisplayName: Airspeed enable
+    // @Description: enable airspeed sensor
+    // @Values: 0:Disable,1:Enable
+    AP_GROUPINFO("ENABLE",    0, AP_Airspeed, _enable),
+
+    // @Param: ARSPD_USE
+    // @DisplayName: Airspeed use
+    // @Description: use airspeed for flight control
+    // @Values: 0:Use,1:Don't Use
+    AP_GROUPINFO("USE",    1, AP_Airspeed, _use),
+
+    // @Param: ARSPD_OFFSET
+    // @DisplayName: Airspeed offset
+    // @Description: Airspeed calibration offset
+    // @Increment: 0.1
+    AP_GROUPINFO("OFFSET", 2, AP_Airspeed, _offset),
+
+    // @Param: ARSPD_RATIO
+    // @DisplayName: Airspeed ratio
+    // @Description: Airspeed calibration ratio
+    // @Increment: 0.1
+    AP_GROUPINFO("RATIO",  3, AP_Airspeed, _ratio),
+
+    AP_GROUPEND
+};
+
+// calibrate the airspeed. This must be called at least once before
+// the get_airspeed() interface can be used
+void AP_Airspeed::calibrate(void (*callback)(unsigned long t))
+{
+	float sum = 0;
+	uint8_t c;
+	if (!_enable) {
+		return;
+	}
+	_source->read();
+	for (c = 0; c < 10; c++) {
+		callback(100);
+		sum += _source->read();
+	}
+	_airspeed_raw = sum/c;
+	_offset.set_and_save(_airspeed_raw);
+	_airspeed = 0;
+}
+
+// read the airspeed sensor
+void AP_Airspeed::read(void)
+{
+	float airspeed_pressure;
+	if (!_enable) {
+		return;
+	}
+	_airspeed_raw 		= _filter.apply(_source->read());
+	airspeed_pressure 	= max((_airspeed_raw - _offset), 0);
+	_airspeed		= sqrt(airspeed_pressure * _ratio);	
+}

libraries/AP_Airspeed/AP_Airspeed.h

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+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+
+#ifndef __AP_AIRSPEED_H__
+#define __AP_AIRSPEED_H__
+
+#include <AP_Common.h>
+#include <AP_Param.h>
+#include <AP_AnalogSource.h>
+#include <Filter.h>
+#include <AverageFilter.h>
+
+class AP_Airspeed
+{
+public:
+	// constructor
+	AP_Airspeed(AP_AnalogSource *source, float ratio, bool enable) {
+		_source = source;
+		_offset.set(0);
+		_ratio.set(ratio);
+        
+        // by default enable but don't use the airspeed sensor
+		_use.set(1);
+		_enable.set(enable?1:0);
+	}
+
+	// read the analog source and update _airspeed
+	void read(void);
+
+	// calibrate the airspeed. This must be called on startup if the
+	// altitude/climb_rate/acceleration interfaces are ever used
+	// the callback is a delay() like routine
+	void calibrate(void (*callback)(unsigned long t));
+
+	// return the current airspeed in m/s
+	float get_airspeed(void) { return _airspeed; }
+
+	// return the current airspeed in cm/s
+	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; }
+
+    // return true if airspeed is enabled
+    bool enabled(void) { return _enable; }
+
+    // used by HIL to set the airspeed
+    void set_HIL(float airspeed) { _airspeed = airspeed; }
+
+	static const struct AP_Param::GroupInfo var_info[];
+
+private:
+	AP_AnalogSource *_source;
+	AP_Float    _offset;
+	AP_Float    _ratio;
+	AP_Int8     _use;
+	AP_Int8     _enable;
+	float	    _airspeed;
+	float	    _airspeed_raw;
+    AverageFilterFloat_Size5 _filter;
+};
+
+
+#endif // __AP_AIRSPEED_H__

libraries/AP_Airspeed/examples/Airspeed/Airspeed.pde

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+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+    Airspeed.pde - airspeed example sketch
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public License
+    as published by the Free Software Foundation; either version 2.1
+    of the License, or (at your option) any later version.
+*/
+
+#include <FastSerial.h>
+#include <AP_Common.h>
+#include <AP_Math.h>
+#include <AP_AnalogSource.h>
+#include <AP_AnalogSource_Arduino.h>
+#include <Arduino_Mega_ISR_Registry.h>
+#include <AP_PeriodicProcess.h>
+#include <Filter.h>
+#include <AP_Airspeed.h>
+
+Arduino_Mega_ISR_Registry isr_registry;
+AP_TimerProcess  scheduler;
+
+FastSerialPort0(Serial);
+
+AP_AnalogSource_Arduino pin0(0);
+AP_Airspeed airspeed(&pin0, 1.9936, true);
+
+void setup()
+{
+	Serial.begin(115200, 128, 128);
+	Serial.println("ArduPilot Airspeed library test");
+
+	isr_registry.init();
+	scheduler.init(&isr_registry);
+	AP_AnalogSource_Arduino::init_timer(&scheduler);
+
+	pinMode(0, INPUT);
+
+	airspeed.calibrate(delay);
+}
+
+void loop(void)
+{
+	static uint32_t timer;
+	if((millis() - timer) > 100){
+		timer = millis();
+		airspeed.read();
+		Serial.printf("airspeed %.2f\n", airspeed.get_airspeed());
+	}
+}

libraries/AP_Airspeed/examples/Airspeed/Makefile

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+include ../../../AP_Common/Arduino.mk