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 |