ardupilot/libraries/AP_RangeFinder/AP_RangeFinder_MaxsonarI2CXL.cpp

// -*- tab-width: 4; Mode: C++; c-basic-offset: 3; indent-tabs-mode: t -*-
/*
 *       AP_RangeFinder_MaxsonarI2CXL.cpp - Arduino Library for MaxBotix I2C XL sonar
 *       Code by Randy Mackay. DIYDrones.com
 *
 *       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.
 *
 *       datasheet: http://www.maxbotix.com/documents/I2CXL-MaxSonar-EZ_Datasheet.pdf
 *
 *       Sensor should be connected to the I2C port
 *
 *       Variables:
 *               bool healthy : indicates whether last communication with sensor was successful
 *
 *       Methods:
 *               take_reading(): ask the sonar to take a new distance measurement
 *               read() : read last distance measured (in cm)
 *
 */

// AVR LibC Includes
#include "AP_RangeFinder_MaxsonarI2CXL.h"
#include <AP_HAL.h>

extern const AP_HAL::HAL& hal;

// Constructor //////////////////////////////////////////////////////////////

AP_RangeFinder_MaxsonarI2CXL::AP_RangeFinder_MaxsonarI2CXL( FilterInt16 *filter ) :
    RangeFinder(NULL, filter),
    healthy(true),
    _addr(AP_RANGE_FINDER_MAXSONARI2CXL_DEFAULT_ADDR)
{
    max_distance = AP_RANGE_FINDER_MAXSONARI2CXL_MIN_DISTANCE;
    min_distance = AP_RANGE_FINDER_MAXSONARI2CXL_MAX_DISTANCE;
}

// Public Methods //////////////////////////////////////////////////////////////

// take_reading - ask sensor to make a range reading
bool AP_RangeFinder_MaxsonarI2CXL::take_reading()
{
    // take range reading and read back results
    uint8_t tosend[1] = 
        { AP_RANGE_FINDER_MAXSONARI2CXL_COMMAND_TAKE_RANGE_READING };
    if (hal.i2c->write(_addr, 1, tosend) != 0) {
        healthy = false;
        return false;
    }else{
        healthy = true;
        return true;
    }
}

// read - return last value measured by sensor
int AP_RangeFinder_MaxsonarI2CXL::read()
{
    uint8_t buff[2];
    int16_t ret_value = 0;

    // take range reading and read back results
    if (hal.i2c->read(_addr, 2, buff) != 0) {
        healthy = false;
    }else{
        // combine results into distance
        ret_value = buff[0] << 8 | buff[1];
        healthy = true;
    }

    return ret_value;
}