Colony

/**

 * Copyright (c) 2007 Colony Project

 * 

 * Permission is hereby granted, free of charge, to any person

 * obtaining a copy of this software and associated documentation

 * files (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use,

 * copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following

 * conditions:

 * 

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 * 

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 **/

/**

 * @file battery.c

 * @brief Implementation for reading battery level

 *

 * Contains functions for reading the battery level.

 *

 * @author Colony Project, CMU Robotics Club

 **/

#include "battery.h"

#include "analog.h"

//Constants for Battery

//Constants determined experimentally 2/9/2007 - James Kong

//See Battery8_data.xls for experiment data

#define BATTERY_NEXT_READ_PRESCALAR 5

#define MAX_LOW_COUNT 5

//global variables

int battery_low_count;

/**

 * @defgroup battery Battery

 * @brief Functions for reading battery voltage.

 * 

 * Contains functions for checking the current

 * voltage of the battery. Include battery.h to

 * access these functions.

 *

 * @{

 **/

/**

 * Returns the voltage of the battery as an analog8

 * reading. 128 is approximately 5 volts. analog_init

 * must be called before using this function.

 *

 * @return the voltage of the battery as an analog8

 * reading

 *

 * @see analog_init, battery, analog8

 **/

int battery8(void)

{

  return analog8(BATT_PORT);

}

/**

 * Returns the voltage of the battery in deciVolts.

 * analog_init must be called before using this function.

 *

 * @return the voltage of the battery in deciVolts.

 *

 * @see analog_init, battery8

 **/

int battery(void)

{

  /* 5 volts is the max, 255 is the max 8bit number , *2 for the divider */

        return analog8(BATT_PORT) * 500 >>7;

}

/**

 * Checks if the battery is low. analog_init must be called before

 * this function can be used. This function waits for several low

 * battery readings in a row to avoid false positives.

 *

 * @return 1 if the battery is low, 0 otherwise

 *

 * @see analog_init

 **/

char battery_low(void)

{

  static char next_read = 0;

  static char ret = 0;

  int batt_reading = battery8();

  if(next_read == 0) {

    if(batt_reading > BATTERY_LOWV)

    {

        ret = 0;

        battery_low_count = 0;

    }

    else

    {

        battery_low_count++;

        if( battery_low_count >= MAX_LOW_COUNT )

        {

            ret = 1;

            battery_low_count = 0;

        }

    }

    next_read = BATTERY_NEXT_READ_PRESCALAR;

  }

  else next_read--;

  return ret;

}

/**

 * Averages n_samples battery8 readings. This function may

 * take a while to complete, and is only made available

 * for convenience. analog_init must be called before this

 * function may be used.

 *

 * @param n_samples the number of times to sample the battery voltage

 *

 * @return the average reading for the battery voltage, where 128

 * is approximately 5 Volts.

 *

 * @see analog_init, battery

 **/

int battery8_avg(int n_samples)

{

  int i;

  long int sum = 0;

  for(i = 0; i < n_samples; i++) {

    sum += battery8();

  }

  return (int)(sum / n_samples);

}

/** @} **/ //end defgroup