ardupilot/libraries/AP_Airspeed/AP_Airspeed_analog.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* analog airspeed driver
*/
#include <AP_HAL/AP_HAL.h>
#include <AP_Common/AP_Common.h>
#include "AP_Airspeed.h"
#include "AP_Airspeed_analog.h"
extern const AP_HAL::HAL &hal;
// scaling for 3DR analog airspeed sensor
#define VOLTS_TO_PASCAL 819
AP_Airspeed_Analog::AP_Airspeed_Analog(AP_Airspeed &_frontend, uint8_t _instance) :
AP_Airspeed_Backend(_frontend, _instance)
{
_source = hal.analogin->channel(get_pin());
}
bool AP_Airspeed_Analog::init()
{
return _source != nullptr;
}
// read the airspeed sensor
bool AP_Airspeed_Analog::get_differential_pressure(float &pressure)
{
if (_source == nullptr) {
return false;
}
// allow pin to change
_source->set_pin(get_pin());
pressure = _source->voltage_average_ratiometric() * VOLTS_TO_PASCAL / get_psi_range();
return true;
}