root / trunk / code / lib / src / libdragonfly / battery.c @ 7
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| 1 | 7 | bcoltin | #include "battery.h" |
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| 2 | #include "analog.h" |
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| 3 | |||
| 4 | //Constants for Battery
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| 5 | //Constants determined experimentally 2/9/2007 - James Kong
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| 6 | //See Battery8_data.xls for experiment data
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| 7 | #define BATTERY_NEXT_READ_PRESCALAR 5 |
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| 8 | #define MAX_LOW_COUNT 5 |
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| 9 | |||
| 10 | //global variables
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| 11 | int battery_low_count;
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| 12 | |||
| 13 | /**
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| 14 | * @defgroup battery Battery
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| 15 | * @brief Functions for reading battery voltage.
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| 16 | *
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| 17 | * Contains functions for checking the current
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| 18 | * voltage of the battery. Include battery.h to
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| 19 | * access these functions.
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| 20 | *
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| 21 | * @{
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| 22 | **/
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| 23 | |||
| 24 | /**
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| 25 | * Returns the voltage of the battery as an analog8
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| 26 | * reading. 128 is approximately 5 volts. analog_init
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| 27 | * must be called before using this function.
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| 28 | *
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| 29 | * @return the voltage of the battery as an analog8
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| 30 | * reading
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| 31 | *
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| 32 | * @see analog_init, battery, analog8
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| 33 | **/
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| 34 | int battery8(void) |
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| 35 | {
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| 36 | return analog8(BATT_PORT);
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| 37 | } |
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| 38 | |||
| 39 | /**
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| 40 | * Returns the voltage of the battery in deciVolts.
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| 41 | * analog_init must be called before using this function.
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| 42 | *
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| 43 | * @return the voltage of the battery in deciVolts.
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| 44 | *
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| 45 | * @see analog_init, battery8
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| 46 | **/
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| 47 | int battery(void) |
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| 48 | {
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| 49 | /* 5 volts is the max, 255 is the max 8bit number , *2 for the divider */
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| 50 | return analog8(BATT_PORT) * 500 >>7; |
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| 51 | } |
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| 52 | |||
| 53 | |||
| 54 | /**
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| 55 | * Checks if the battery is low. analog_init must be called before
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| 56 | * this function can be used. This function waits for several low
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| 57 | * battery readings in a row to avoid false positives.
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| 58 | *
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| 59 | * @return 1 if the battery is low, 0 otherwise
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| 60 | *
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| 61 | * @see analog_init
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| 62 | **/
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| 63 | char battery_low(void) |
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| 64 | {
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| 65 | static char next_read = 0; |
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| 66 | static char ret = 0; |
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| 67 | |||
| 68 | int batt_reading = battery8();
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| 69 | |||
| 70 | if(next_read == 0) { |
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| 71 | if(batt_reading > BATTERY_LOWV)
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| 72 | {
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| 73 | ret = 0;
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| 74 | battery_low_count = 0;
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| 75 | } |
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| 76 | else
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| 77 | {
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| 78 | battery_low_count++; |
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| 79 | if( battery_low_count >= MAX_LOW_COUNT )
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| 80 | {
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| 81 | ret = 1;
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| 82 | battery_low_count = 0;
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| 83 | } |
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| 84 | } |
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| 85 | |||
| 86 | next_read = BATTERY_NEXT_READ_PRESCALAR; |
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| 87 | } |
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| 88 | else next_read--;
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| 89 | |||
| 90 | return ret;
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| 91 | } |
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| 92 | |||
| 93 | /**
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| 94 | * Averages n_samples battery8 readings. This function may
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| 95 | * take a while to complete, and is only made available
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| 96 | * for convenience. analog_init must be called before this
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| 97 | * function may be used.
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| 98 | *
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| 99 | * @param n_samples The number of times to sample the battery voltage
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| 100 | *
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| 101 | * @return the average reading for the battery voltage, where 128
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| 102 | * is approximately 5 Volts.
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| 103 | *
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| 104 | * @see analog_init, battery
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| 105 | **/
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| 106 | int battery8_avg(int n_samples) |
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| 107 | {
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| 108 | int i;
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| 109 | long int sum = 0; |
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| 110 | |||
| 111 | for(i = 0; i < n_samples; i++) { |
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| 112 | sum += battery8(); |
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| 113 | } |
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| 114 | |||
| 115 | return (int)(sum / n_samples); |
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| 116 | } |
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| 117 | |||
| 118 | /** @} **/ //end defgroup |