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/*
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time.c
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anything that requires a delay
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mostly delay_ms
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author: Robotics Club, Colony Project
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Change Log:
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2.5.07 - Kevin
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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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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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You now count how many 16ths of a second you want until you trigger your actual interrupt. Works. Changed defines
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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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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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it used to
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1.30.07 - Kevin
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Modified the clock to run on timer3 on the Dragonfly. Works with decent accuracy. Using a prescaler of 256
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the timer counts up to a precomputer value which will trigger an interrupt and reset the timer. Multiples of
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256 change it by that multiple. Refer to the time.h file for all possible prescalers.
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The interrupt will call a specified function _rtc_func every pulse.
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All of it has been tested and it works.
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*/
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#include <avr/interrupt.h> |
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#include <util/delay.h> |
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#include <time.h> |
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#include <serial.h> |
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static volatile int _rtc_val = 0; |
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static volatile int _rtc_pulse = 0; |
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static volatile int _rtc_scale = 32; //Defaults to 1 Second per pulse |
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static void (*_rtc_f)(void) = 0; |
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/**
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* @defgroup time Time
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* @brief Time functions
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*
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* Functions dealing with time.
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*
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* @{
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**/
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/**
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* Delays for the specified number of milliseconds.
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* The accuracy of this function is unknown.
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*
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* @param ms the number of milliseconds to delay for
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**/
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void delay_ms(int ms) |
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{ |
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for(; ms > 15; ms-=15) |
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_delay_ms(15);
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_delay_ms(ms); |
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} |
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/* Prescales defined in time.h. SECOND will give you 1 second.
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More scales are defined in the time.h file.
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rtc_func is the address to a function that you want called every clock tick. */
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/**
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* Initializes the real time clock. Prescales are defined in time.h.
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* For example, SECOND will give 1 second. The specified function is
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* called every clock tick. For the real time clock to activate,
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* interrupts must be enabled. (through sei() )
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*
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* @param prescale_opt the period with which the timer is triggered
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* @param rtc_func the function called when the timer is triggered
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*
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* @see rtc_get, rtc_reset
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*
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**/
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void rtc_init(int prescale_opt, void (*rtc_func)(void)) { |
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//Clear timer register for Timer 3
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TCNT3 = 0;
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/* This sets the Waveform Generation Module to CTC (Clear Timer on Compare) Mode (100)
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See page135 in Atmega128 Docs for more modes and explanations */
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TCCR3B |= _BV(WGM32); |
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/* This sets the prescaler for the system clock (8MHz) ie: divides the clock by some number.
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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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See page137 in Atemga128 Docs for all the available prescalers */
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TCCR3B |= _BV(CS31); |
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/* Sets the two regsiters that we compare against. So the timer counts up to this number and
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then resets back to 0 and calls the compare match interrupt.
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8x10^6 / 8 = 1/16 Second. All values are based off of this number. Do not change it unless you
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are l337*/
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OCR3A = 0xF424;
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/* Enable Output Compare A Interrupt. When OCR3A is met by the timer TCNT3 this interrupt will be
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triggerd. (See page140 in Atmega128 Docs for more information */
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ETIMSK |= _BV(OCIE3A); |
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/* Store the pointer to the function to be used in the interrupt */
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_rtc_f = rtc_func; |
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/* Store how many 1/16ths of a second you want to let by before triggering an interrupt */
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_rtc_scale = prescale_opt; |
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} |
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/**
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* Returns the time elapsed in seconds since the last call to
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* rtc_init or rtc_reset.
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*
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* @return the number of seconds since the last call to rtc_init or rtc_reset
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*
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* @see rtc_init, rtc_reset
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**/
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int rtc_get(void){ |
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return _rtc_val;
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} |
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/**
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* Resets the real time clock counter to 0.
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*
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* @see rtc_init, rtc_get
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**/
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void rtc_reset(void){ |
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_rtc_val = 0;
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} |
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/** @} **/ //end defgroup |
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/* Called every pulse. Function in _rtc_f is called every _rtc_scale and also the counter is updated.
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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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and when it reaches the amount of time you want, execute the code. */
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SIGNAL(TIMER3_COMPA_vect) { |
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if (_rtc_pulse == _rtc_scale) {
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//Increment the real time clock counter
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_rtc_val++; |
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//Calls the function tied to the real time clock if defined
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if(_rtc_f != 0) |
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_rtc_f(); |
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//Resets the pulse until the next scale is matched
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_rtc_pulse = 0;
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} |
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//Updates the amount of pulses seen since the last scale match
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_rtc_pulse++; |
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} |
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