ardupilot/libraries/AP_RangeFinder/RangeFinder_Backend.cpp

/*
   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/>.
 */

#include <AP_Common/AP_Common.h>
#include <AP_HAL/AP_HAL.h>
#include "RangeFinder.h"
#include "RangeFinder_Backend.h"

extern const AP_HAL::HAL& hal;

/*
  base class constructor. 
  This incorporates initialisation as well.
*/
AP_RangeFinder_Backend::AP_RangeFinder_Backend(RangeFinder &_ranger, uint8_t instance, RangeFinder::RangeFinder_State &_state, MAV_DISTANCE_SENSOR _sensor_type) :
        ranger(_ranger),
        state(_state),
        sensor_type(_sensor_type)
{
    _sem = hal.util->new_semaphore();    
}

// update status based on distance measurement
void AP_RangeFinder_Backend::update_status()
{
    // check distance
    if ((int16_t)state.distance_cm > ranger._max_distance_cm[state.instance]) {
        set_status(RangeFinder::RangeFinder_OutOfRangeHigh);
    } else if ((int16_t)state.distance_cm < ranger._min_distance_cm[state.instance]) {
        set_status(RangeFinder::RangeFinder_OutOfRangeLow);
    } else {
        set_status(RangeFinder::RangeFinder_Good);
    }
}

// set status and update valid count
void AP_RangeFinder_Backend::set_status(RangeFinder::RangeFinder_Status status)
{
    state.status = status;

    // update valid count
    if (status == RangeFinder::RangeFinder_Good) {
        if (state.range_valid_count < 10) {
            state.range_valid_count++;
        }
    } else {
        state.range_valid_count = 0;
    }
}