root / trunk / code / projects / libdragonfly / battery.c @ 8
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#include "battery.h" |
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#include "analog.h" |
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//Constants for Battery
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//Constants determined experimentally 2/9/2007 - James Kong
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//See Battery8_data.xls for experiment data
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#define BATTERY_NEXT_READ_PRESCALAR 5 |
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#define MAX_LOW_COUNT 5 |
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//global variables
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int battery_low_count;
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/**
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* @defgroup battery Battery
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* @brief Functions for reading battery voltage.
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*
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* Contains functions for checking the current
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* voltage of the battery. Include battery.h to
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* access these functions.
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*
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* @{
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**/
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/**
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* Returns the voltage of the battery as an analog8
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* reading. 128 is approximately 5 volts. analog_init
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* must be called before using this function.
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*
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* @return the voltage of the battery as an analog8
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* reading
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*
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* @see analog_init, battery, analog8
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**/
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int battery8(void) |
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{ |
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return analog8(BATT_PORT);
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} |
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/**
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* Returns the voltage of the battery in deciVolts.
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* analog_init must be called before using this function.
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*
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* @return the voltage of the battery in deciVolts.
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*
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* @see analog_init, battery8
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**/
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int battery(void) |
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{ |
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/* 5 volts is the max, 255 is the max 8bit number , *2 for the divider */
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return analog8(BATT_PORT) * 500 >>7; |
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} |
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/**
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* Checks if the battery is low. analog_init must be called before
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* this function can be used. This function waits for several low
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* battery readings in a row to avoid false positives.
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*
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* @return 1 if the battery is low, 0 otherwise
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*
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* @see analog_init
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**/
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char battery_low(void) |
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{ |
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static char next_read = 0; |
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static char ret = 0; |
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int batt_reading = battery8();
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if(next_read == 0) { |
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if(batt_reading > BATTERY_LOWV)
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{ |
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ret = 0;
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battery_low_count = 0;
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} |
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else
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{ |
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battery_low_count++; |
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if( battery_low_count >= MAX_LOW_COUNT )
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{ |
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ret = 1;
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battery_low_count = 0;
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} |
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} |
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next_read = BATTERY_NEXT_READ_PRESCALAR; |
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} |
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else next_read--;
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return ret;
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} |
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/**
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* Averages n_samples battery8 readings. This function may
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* take a while to complete, and is only made available
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* for convenience. analog_init must be called before this
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* function may be used.
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*
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* @param n_samples The number of times to sample the battery voltage
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*
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* @return the average reading for the battery voltage, where 128
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* is approximately 5 Volts.
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*
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* @see analog_init, battery
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**/
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int battery8_avg(int n_samples) |
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{ |
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int i;
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long int sum = 0; |
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for(i = 0; i < n_samples; i++) { |
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sum += battery8(); |
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} |
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return (int)(sum / n_samples); |
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} |
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/** @} **/ //end defgroup |
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