root / demos / hunter_prey / lib / src / libdragonfly / time.c @ 1828
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1 | 1828 | emullini | /**
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2 | * Copyright (c) 2007 Colony Project
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3 | *
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4 | * Permission is hereby granted, free of charge, to any person
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5 | * obtaining a copy of this software and associated documentation
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6 | * files (the "Software"), to deal in the Software without
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7 | * restriction, including without limitation the rights to use,
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8 | * copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 | * copies of the Software, and to permit persons to whom the
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10 | * Software is furnished to do so, subject to the following
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11 | * conditions:
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12 | *
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13 | * The above copyright notice and this permission notice shall be
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14 | * included in all copies or substantial portions of the Software.
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15 | *
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16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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17 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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18 | * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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19 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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20 | * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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21 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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22 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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23 | * OTHER DEALINGS IN THE SOFTWARE.
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24 | **/
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25 | |||
26 | |||
27 | /**
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28 | * @file time.c
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29 | * @brief Timer code
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30 | *
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31 | * Implementation of functions for timers.
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32 | *
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33 | * @author Colony Project, CMU Robotics Club
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34 | **/
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35 | |||
36 | /*
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37 | time.c
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38 | anything that requires a delay
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39 | mostly delay_ms
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40 | |||
41 | author: Robotics Club, Colony Project
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42 | |||
43 | Change Log:
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44 | 2.5.07 - Kevin
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45 | 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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46 | 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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47 | You now count how many 16ths of a second you want until you trigger your actual interrupt. Works. Changed defines
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48 | 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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49 | 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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50 | it used to
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51 | 1.30.07 - Kevin
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52 | Modified the clock to run on timer3 on the Dragonfly. Works with decent accuracy. Using a prescaler of 256
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53 | the timer counts up to a precomputer value which will trigger an interrupt and reset the timer. Multiples of
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54 | 256 change it by that multiple. Refer to the time.h file for all possible prescalers.
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55 | The interrupt will call a specified function _rtc_func every pulse.
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56 | All of it has been tested and it works.
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57 | |||
58 | */
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59 | #include <avr/interrupt.h> |
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60 | #include <util/delay.h> |
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61 | #include "time.h" |
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62 | |||
63 | |||
64 | /* Calculate how many cycles to delay for to get 1 ms. Based on F_CPU which should be defined by the makefile */
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65 | #ifdef F_CPU
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66 | #define WAIT_CYCLES ((F_CPU / 1000) / 10) |
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67 | #else
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68 | #define WAIT_CYCLES (8000 / 10) |
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69 | #endif
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70 | |||
71 | static volatile int _rtc_val = 0; |
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72 | static volatile int _rtc_pulse = 0; |
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73 | static volatile int _rtc_scale = 32; //Defaults to 1 Second per pulse |
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74 | static void (*_rtc_f)(void) = 0; |
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75 | |||
76 | |||
77 | |||
78 | /**
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79 | * @defgroup time Time
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80 | * @brief Time functions
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81 | *
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82 | * Functions dealing with time.
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83 | *
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84 | * @{
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85 | **/
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86 | |||
87 | /**
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88 | * Delays for the specified number of milliseconds.
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89 | * It depends on F_CPU to be defined in order to calculate how many cycles
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90 | * it should delay. If it is not defined, a default clock of 8MHz is assumed.
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91 | *
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92 | * We use _delay_loop_2 which will run assembly instructions that should be
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93 | * 4 cycles long. Optimizations must be enabled for this to be true.
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94 | * That function is called to ensure around 1ms per execution. To generate
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95 | * multiple ms we run a for loop of how many milliseconds are desired.
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96 | *
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97 | * The error should be just the skew on the oscillator as the formula to
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98 | * calculate delay cycles should always be a whole number. The is some skew
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99 | * in practice though it is unavoidable. Delaying for less than 1s should make
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100 | * the error negligable.
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101 | *
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102 | * @param ms the number of milliseconds to delay for
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103 | **/
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104 | void delay_ms(int ms) { |
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105 | for (; ms > 0; ms--) { |
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106 | _delay_loop_2(WAIT_CYCLES); |
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107 | } |
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108 | } |
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109 | |||
110 | |||
111 | /* Prescales defined in time.h. SECOND will give you 1 second.
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112 | More scales are defined in the time.h file.
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113 | rtc_func is the address to a function that you want called every clock tick. */
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114 | /**
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115 | * Initializes the real time clock. Prescales are defined in time.h.
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116 | * For example, SECOND will give 1 second. The specified function is
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117 | * called every clock tick. For the real time clock to activate,
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118 | * interrupts must be enabled. (through sei() )
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119 | *
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120 | * @param prescale_opt the period with which the timer is triggered
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121 | * @param rtc_func the function called when the timer is triggered
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122 | *
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123 | * @see rtc_get, rtc_reset
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124 | *
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125 | **/
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126 | void rtc_init(int prescale_opt, void (*rtc_func)(void)) { |
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127 | |||
128 | //Clear timer register for Timer 3
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129 | TCNT3 = 0;
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130 | |||
131 | /* This sets the Waveform Generation Module to CTC (Clear Timer on Compare) Mode (100)
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132 | See page135 in Atmega128 Docs for more modes and explanations */
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133 | TCCR3B |= _BV(WGM32); |
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134 | |||
135 | /* This sets the prescaler for the system clock (8MHz) ie: divides the clock by some number.
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136 | 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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137 | See page137 in Atemga128 Docs for all the available prescalers */
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138 | TCCR3B |= _BV(CS31); |
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139 | |||
140 | /* Sets the two regsiters that we compare against. So the timer counts up to this number and
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141 | then resets back to 0 and calls the compare match interrupt.
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142 | 8x10^6 / 8 = 1/16 Second. All values are based off of this number. Do not change it unless you
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143 | are l337*/
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144 | |||
145 | OCR3A = 0xF424;
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146 | |||
147 | /* Enable Output Compare A Interrupt. When OCR3A is met by the timer TCNT3 this interrupt will be
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148 | triggerd. (See page140 in Atmega128 Docs for more information */
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149 | ETIMSK |= _BV(OCIE3A); |
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150 | |||
151 | /* Store the pointer to the function to be used in the interrupt */
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152 | _rtc_f = rtc_func; |
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153 | |||
154 | /* Store how many 1/16ths of a second you want to let by before triggering an interrupt */
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155 | _rtc_scale = prescale_opt; |
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156 | } |
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157 | |||
158 | /**
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159 | * Returns the time elapsed in seconds since the last call to
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160 | * rtc_init or rtc_reset.
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161 | *
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162 | * @return the number of seconds since the last call to rtc_init or rtc_reset
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163 | *
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164 | * @see rtc_init, rtc_reset
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165 | **/
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166 | int rtc_get(void) { |
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167 | return _rtc_val;
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168 | } |
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169 | |||
170 | /**
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171 | * Resets the real time clock counter to 0.
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172 | *
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173 | * @see rtc_init, rtc_get
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174 | **/
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175 | void rtc_reset(void) { |
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176 | _rtc_val = 0;
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177 | } |
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178 | |||
179 | /** @} **/ //end defgroup |
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180 | |||
181 | /* Called every pulse. Function in _rtc_f is called every _rtc_scale and also the counter is updated.
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182 | 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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183 | and when it reaches the amount of time you want, execute the code. */
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184 | SIGNAL(TIMER3_COMPA_vect) { |
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185 | |||
186 | if (_rtc_pulse == _rtc_scale) {
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187 | //Increment the real time clock counter
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188 | _rtc_val++; |
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189 | |||
190 | //Calls the function tied to the real time clock if defined
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191 | if(_rtc_f != 0) |
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192 | _rtc_f(); |
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193 | |||
194 | //Resets the pulse until the next scale is matched
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195 | _rtc_pulse = 0;
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196 | } |
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197 | |||
198 | //Updates the amount of pulses seen since the last scale match
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199 | _rtc_pulse++; |
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200 | |||
201 | } |