time.c File Reference

Contains functions to initialize, set, poll and stop timers. More...

#include "config.h"
#include "time.h"

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Functions
__interrupt void	TICK_ISR (void)
	Interrupt service routine for timer 0 overflow.
unsigned char	Time_Left (unsigned char timer)
	Checks if a specified timer has expired.
void	Time_Set (unsigned char timer, unsigned int min, unsigned char sec, unsigned char ms)
	Sets the specified timer.
void	Time_Stop (void)
	Stops timers.
void	Time_Start (void)
	Starts timers.
void	Time_Init (void)
	Initializes timers.
Variables
unsigned long	timeval [TIMERS]
	Contains the values for each timer.

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Detailed Description

Contains functions to initialize, set, poll and stop timers.

• Compiler: IAR EWAVR and GNU GCC for AVR
• Supported devices: ATmega32U4

Author:

Atmel Corporation: http://www.atmel.com
Support and FAQ: http://support.atmel.no/

Definition in file time.c.

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Function Documentation

__interrupt void TICK_ISR

(

void

)

Interrupt service routine for timer 0 overflow.

Timer 0 runs at 125 kHz and compare match will occur every millisecond (125 / 125 kHz = 1.0 ms), which will result in a call to this function. When called, this function will decrement the time left for each timer, unless they are already at zero.

Definition at line 71 of file time.c.

References timeval.

{
   unsigned char i;

   // 1 ms has passed, decrement all non-zero timers.
   for (i = 0; i < TIMERS; i++) {
      if(timeval[i] > 0) {
         timeval[i]--;
      }
   }
}

unsigned char Time_Left

(

unsigned char

timer )

Checks if a specified timer has expired.

Parameters:

timer

Specifies timer

Return values:

TRUE	Timer still going.
FALSE	Timer has expired.

Definition at line 92 of file time.c.

References FALSE, timeval, and TRUE.

Referenced by PWM_Start().

{
   if(timeval[timer] > 0) {
      return(TRUE);
   } else {
      return(FALSE);
   }
}

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void Time_Set	(	unsigned char	timer,
		unsigned int	min,
		unsigned char	sec,
		unsigned char	ms
	)

Sets the specified timer.

Parameters:

timer	Specifies timer
min	Minutes for timer to count down
sec	Seconds for timer to count down
ms	Milliseconds for timer to count down

Definition at line 109 of file time.c.

References timeval.

Referenced by PWM_Start().

{
   timeval[timer] = 60000 * (unsigned long)min;
   timeval[timer] += 1000 * (unsigned long)sec;
   timeval[timer] += 1 * (unsigned long)ms;
}

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void Time_Stop

(

void

)

Stops timers.

Sets timer0's clock source to none.

Definition at line 122 of file time.c.

{
   TCCR0B = 0;
}

void Time_Start

(

void

)

Starts timers.

Sets timer0's clock source to system clock divided by 64.

Definition at line 132 of file time.c.

Referenced by PWM_Start().

{
   TCNT0 = 0x00;//cgs added 
   TCCR0B = (0<<CS02)|(1<<CS01)|(1<<CS00);   // CLKT0 = CLK/64 = 125 kHz.
}

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void Time_Init

(

void

)

Initializes timers.

Resets all the timer values to 0, then sets up timer 0 for a compare match every millisecond.

Definition at line 144 of file time.c.

References timeval.

{
   unsigned char i;
   
   for (i = 0; i<<TIMERS; i++)   {
      timeval[i] = 0;
   }
   
   OCR0A = 125;  // Will give a compare match every ms.
   
   OCR0B = 0;  // Doesn't matter, will run in normal mode.

   TCCR0A = (1<<WGM00);  // 8-bit CTC mode.
      
   TCCR0B = (0<<CS02)|(1<<CS01)|(1<<CS00);   // CLKT0 = CLK/64 = 125 kHz.

   TIMSK0 |= (1<<OCIE0A);  // Timer 0, Compare match A interrupt enabled.

   // Enable interrupts, just in case they weren't already. 
#ifdef __GNUC__
   Enable_interrupt();
#else
   __enable_interrupt();
#endif         
}

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Variable Documentation

unsigned long timeval[TIMERS]

Contains the values for each timer.

Definition at line 51 of file time.c.

Referenced by TICK_ISR(), Time_Init(), Time_Left(), and Time_Set().