ardupilot/libraries/AP_RangeFinder/RangeFinder.cpp

// -*- tab-width: 4; Mode: C++; c-basic-offset: 3; indent-tabs-mode: t -*-
/*
	AP_RangeFinder.cpp - Arduino Library for Sharpe GP2Y0A02YK0F
	infrared proximity sensor
	Code by Jose Julio and 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.

	This has the basic functions that all RangeFinders need implemented
*/

// AVR LibC Includes
#include "WConstants.h"
#include "RangeFinder.h"

// Constructor /////////////////////////////////////////////////////////////////
RangeFinder::RangeFinder() :
	_ap_adc(NULL),
	_num_averages(AP_RANGEFINDER_NUM_AVERAGES),
	_history_ptr(0)
{
}

// Public Methods //////////////////////////////////////////////////////////////
void RangeFinder::init(int analogPort, AP_ADC *ap_adc)
{
    // local variables
    int i;

    // store the analog port to be used
    _analogPort = analogPort;

	// set the given analog port to an input
	if( analogPort != AP_RANGEFINDER_PITOT_TUBE ){
	    pinMode(analogPort, INPUT);
    }else{
	    _num_averages = 0;  // turn off averaging for pitot tube because AP_ADC does this for us
	}

	// capture the AP_ADC object if passed in
	if( ap_adc != NULL )
	    _ap_adc = ap_adc;

	// make first call to read to get initial distance
	read();

	// initialise history
	for(i = 0; i < AP_RANGEFINDER_NUM_AVERAGES; i++)
	    _history[i] = distance;
}

void RangeFinder::set_orientation(int x, int y, int z)
{
    orientation_x = x;
	orientation_y = y;
	orientation_z = z;
}

// Read Sensor data - only the raw_value is filled in by this parent class
int RangeFinder::read()
{
    // local variables
	int temp_dist;
	int total = 0;
	int i;

	// read from the analog port or pitot tube
	if(_analogPort == AP_RANGEFINDER_PITOT_TUBE){
		if(_ap_adc != NULL){
			raw_value = _ap_adc->Ch(AP_RANGEFINDER_PITOT_TUBE_ADC_CHANNEL) >> 2;  // values from ADC are twice as big as you'd expect
		}else{
			raw_value = 0;
		}

		// convert analog value to distance in cm (using child implementation most likely)
		temp_dist = convert_raw_to_distance(raw_value);

		// ensure distance is within min and max
		distance = constrain(temp_dist, min_distance, max_distance);

		// return distance
		return distance;

	}else{

        // read raw sensor value and convert to distance
        raw_value = analogRead(_analogPort);

		// convert analog value to distance in cm (using child implementation most likely)
		temp_dist = convert_raw_to_distance(raw_value);

		// ensure distance is within min and max
		distance = constrain(temp_dist, min_distance, max_distance);

		// filter the results
		if( _num_averages > 1 ){
			_history_ptr = (_history_ptr + 1) % _num_averages;
			_history[_history_ptr] = distance;
			for(i = 0; i < _num_averages; i++ ) total += _history[i];
			distance = total / _num_averages;
		}

		// return distance
		return distance;
	}
}