mirror of https://github.com/ArduPilot/ardupilot
86 lines
2.5 KiB
C++
86 lines
2.5 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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* APM_Airspeed.cpp - airspeed (pitot) driver
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 2.1
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* of the License, or (at your option) any later version.
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*/
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#include <AP_Math.h>
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#include <AP_Common.h>
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#include <AP_HAL.h>
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#include <AP_Airspeed.h>
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extern const AP_HAL::HAL& hal;
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// table of user settable parameters
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const AP_Param::GroupInfo AP_Airspeed::var_info[] PROGMEM = {
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// @Param: ENABLE
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// @DisplayName: Airspeed enable
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// @Description: enable airspeed sensor
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// @Values: 0:Disable,1:Enable
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AP_GROUPINFO("ENABLE", 0, AP_Airspeed, _enable, 1),
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// @Param: USE
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// @DisplayName: Airspeed use
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// @Description: use airspeed for flight control
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// @Values: 1:Use,0:Don't Use
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AP_GROUPINFO("USE", 1, AP_Airspeed, _use, 0),
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// @Param: OFFSET
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// @DisplayName: Airspeed offset
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// @Description: Airspeed calibration offset
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// @Increment: 0.1
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AP_GROUPINFO("OFFSET", 2, AP_Airspeed, _offset, 0),
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// @Param: RATIO
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// @DisplayName: Airspeed ratio
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// @Description: Airspeed calibration ratio
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// @Increment: 0.1
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AP_GROUPINFO("RATIO", 3, AP_Airspeed, _ratio, 1.9936f),
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AP_GROUPEND
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};
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/*
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this scaling factor converts from the old system where we used a
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0 to 4095 raw ADC value for 0-5V to the new system which gets the
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voltage in volts directly from the ADC driver
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*/
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#define SCALING_OLD_CALIBRATION 819 // 4095/5
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// calibrate the airspeed. This must be called at least once before
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// the get_airspeed() interface can be used
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void AP_Airspeed::calibrate()
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{
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float sum = 0;
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uint8_t c;
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if (!_enable) {
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return;
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}
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_source->voltage_average_ratiometric();
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for (c = 0; c < 10; c++) {
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hal.scheduler->delay(100);
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sum += _source->voltage_average_ratiometric() * SCALING_OLD_CALIBRATION;
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}
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float raw = sum/c;
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_offset.set_and_save(raw);
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_airspeed = 0;
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}
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// read the airspeed sensor
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void AP_Airspeed::read(void)
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{
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float airspeed_pressure;
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if (!_enable) {
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return;
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}
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float raw = _source->voltage_average_ratiometric() * SCALING_OLD_CALIBRATION;
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airspeed_pressure = max(raw - _offset, 0);
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float new_airspeed = sqrtf(airspeed_pressure * _ratio);
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_airspeed = 0.7f * _airspeed + 0.3f * new_airspeed;
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}
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