root / branches / lib_additions / code / lib / src / libdragonfly / time.c @ 79
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1 | 7 | bcoltin | /*
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2 | time.c
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3 | anything that requires a delay
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4 | mostly delay_ms
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5 | |||
6 | author: Robotics Club, Colony Project
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7 | |||
8 | Change Log:
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9 | 2.5.07 - Kevin
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10 | Aaron fixed the orb/servo code and made them use timer3 but compare registers B and C. He hard set the prescaler
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11 | to 8 so the RTC broke. Changed it so that we use a 8 prescaler which sets the compare match at 1/16th of a second.
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12 | You now count how many 16ths of a second you want until you trigger your actual interrupt. Works. Changed defines
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13 | for time so you can still call rtc_init with a scale but now it is defined in terms of actual time like second, quarter_second
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14 | etc. Read that section in the time.h file for more information. Tested and works, though the clock drifts more than
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15 | it used to
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16 | 1.30.07 - Kevin
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17 | Modified the clock to run on timer3 on the Dragonfly. Works with decent accuracy. Using a prescaler of 256
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18 | the timer counts up to a precomputer value which will trigger an interrupt and reset the timer. Multiples of
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19 | 256 change it by that multiple. Refer to the time.h file for all possible prescalers.
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20 | The interrupt will call a specified function _rtc_func every pulse.
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21 | All of it has been tested and it works.
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22 | |||
23 | */
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24 | #include <avr/interrupt.h> |
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25 | #include <util/delay.h> |
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26 | #include <time.h> |
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27 | #include <serial.h> |
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28 | |||
29 | static volatile int _rtc_val = 0; |
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30 | static volatile int _rtc_pulse = 0; |
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31 | static volatile int _rtc_scale = 32; //Defaults to 1 Second per pulse |
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32 | static void (*_rtc_f)(void) = 0; |
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33 | |||
34 | /**
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35 | * @defgroup time Time
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36 | * @brief Time functions
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37 | *
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38 | * Functions dealing with time.
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39 | *
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40 | * @{
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41 | **/
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42 | |||
43 | /**
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44 | * Delays for the specified number of milliseconds.
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45 | * The accuracy of this function is unknown.
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46 | *
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47 | * @param ms the number of milliseconds to delay for
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48 | **/
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49 | void delay_ms(int ms) |
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50 | { |
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51 | for(; ms > 15; ms-=15) |
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52 | _delay_ms(15);
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53 | _delay_ms(ms); |
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54 | } |
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55 | |||
56 | |||
57 | /* Prescales defined in time.h. SECOND will give you 1 second.
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58 | More scales are defined in the time.h file.
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59 | rtc_func is the address to a function that you want called every clock tick. */
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60 | /**
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61 | * Initializes the real time clock. Prescales are defined in time.h.
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62 | * For example, SECOND will give 1 second. The specified function is
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63 | * called every clock tick. For the real time clock to activate,
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64 | * interrupts must be enabled. (through sei() )
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65 | *
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66 | * @param prescale_opt the period with which the timer is triggered
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67 | * @param rtc_func the function called when the timer is triggered
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68 | *
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69 | * @see rtc_get, rtc_reset
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70 | *
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71 | **/
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72 | void rtc_init(int prescale_opt, void (*rtc_func)(void)) { |
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73 | |||
74 | //Clear timer register for Timer 3
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75 | TCNT3 = 0;
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76 | |||
77 | /* This sets the Waveform Generation Module to CTC (Clear Timer on Compare) Mode (100)
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78 | See page135 in Atmega128 Docs for more modes and explanations */
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79 | TCCR3B |= _BV(WGM32); |
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80 | |||
81 | /* This sets the prescaler for the system clock (8MHz) ie: divides the clock by some number.
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82 | Currently set to a prescaler of 8 because that is what the orb and servos use (they are on this timer as well)
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83 | See page137 in Atemga128 Docs for all the available prescalers */
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84 | TCCR3B |= _BV(CS31); |
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85 | |||
86 | /* Sets the two regsiters that we compare against. So the timer counts up to this number and
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87 | then resets back to 0 and calls the compare match interrupt.
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88 | 8x10^6 / 8 = 1/16 Second. All values are based off of this number. Do not change it unless you
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89 | are l337*/
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90 | |||
91 | OCR3A = 0xF424;
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92 | |||
93 | /* Enable Output Compare A Interrupt. When OCR3A is met by the timer TCNT3 this interrupt will be
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94 | triggerd. (See page140 in Atmega128 Docs for more information */
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95 | ETIMSK |= _BV(OCIE3A); |
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96 | |||
97 | /* Store the pointer to the function to be used in the interrupt */
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98 | _rtc_f = rtc_func; |
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99 | |||
100 | /* Store how many 1/16ths of a second you want to let by before triggering an interrupt */
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101 | _rtc_scale = prescale_opt; |
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102 | } |
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103 | |||
104 | /**
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105 | * Returns the time elapsed in seconds since the last call to
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106 | * rtc_init or rtc_reset.
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107 | *
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108 | * @return the number of seconds since the last call to rtc_init or rtc_reset
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109 | *
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110 | * @see rtc_init, rtc_reset
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111 | **/
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112 | int rtc_get(void){ |
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113 | return _rtc_val;
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114 | } |
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115 | |||
116 | /**
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117 | * Resets the real time clock counter to 0.
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118 | *
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119 | * @see rtc_init, rtc_get
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120 | **/
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121 | void rtc_reset(void){ |
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122 | _rtc_val = 0;
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123 | } |
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124 | |||
125 | /** @} **/ //end defgroup |
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126 | |||
127 | /* Called every pulse. Function in _rtc_f is called every _rtc_scale and also the counter is updated.
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128 | Bascially, since the pulse is hard set at 1/16s you want to count how many 16ths of a second have passed
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129 | and when it reaches the amount of time you want, execute the code. */
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130 | SIGNAL(TIMER3_COMPA_vect) { |
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131 | |||
132 | if (_rtc_pulse == _rtc_scale) {
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133 | //Increment the real time clock counter
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134 | _rtc_val++; |
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135 | |||
136 | //Calls the function tied to the real time clock if defined
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137 | if(_rtc_f != 0) |
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138 | _rtc_f(); |
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139 | |||
140 | //Resets the pulse until the next scale is matched
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141 | _rtc_pulse = 0;
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142 | } |
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143 | |||
144 | //Updates the amount of pulses seen since the last scale match
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145 | _rtc_pulse++; |
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146 | |||
147 | } |