Time

Time functions. More...

Defines
#define	SIXTEENTH_SECOND   1
	A sixteenth of a second.
#define	EIGTH_SECOND   2
	An eighth of a second.
#define	QUARTER_SECOND   4
	A quarter of a second.
#define	HALF_SECOND   8
	Half of a second.
#define	SECOND   16
	One second.
#define	TWO_SECOND   32
	Two seconds.
#define	FOUR_SECOND   64
	Four seconds.
Functions
void	delay_ms (int ms)
	Delay execution for the specified time.
void	rtc_init (int prescale_opt, void(*rtc_func)(void))
	Enable the realtime clock.
int	rtc_get (void)
	Get the value of the realtime clock.
void	rtc_reset (void)
	Reset the counter of the realtime clock.

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Detailed Description

Time functions.

Functions dealing with time.

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Function Documentation

void delay_ms

(

int

ms

)

Delay execution for the specified time.

Delays for the specified number of milliseconds. It depends on F_CPU to be defined in order to calculate how many cycles it should delay. If it is not defined, a default clock of 8MHz is assumed.

We use _delay_loop_2 which will run assembly instructions that should be 4 cycles long. Optimizations must be enabled for this to be true. That function is called to ensure around 1ms per execution. To generate multiple ms we run a for loop of how many milliseconds are desired.

The error should be just the skew on the oscillator as the formula to calculate delay cycles should always be a whole number. The is some skew in practice though it is unavoidable. Delaying for less than 1s should make the error negligable.

Parameters:

ms

the number of milliseconds to delay for

Referenced by button1_wait(), button2_wait(), buzzer_chirp(), flash_red(), lcd_init(), and odometry_init().

int rtc_get

(

void

)

Get the value of the realtime clock.

Returns the time elapsed in seconds since the last call to rtc_init or rtc_reset.

Returns:

the number of seconds since the last call to rtc_init or rtc_reset

See also:

rtc_init, rtc_reset

void rtc_init	(	int	prescale_opt,
		void(*)(void)	rtc_func
	)

Enable the realtime clock.

Initializes the real time clock. Prescales are defined in time.h. For example, SECOND will give 1 second. The specified function is called every clock tick. For the real time clock to activate, interrupts must be enabled. (through sei() )

Parameters:

	prescale_opt	the period with which the timer is triggered
	rtc_func	the function called when the timer is triggered

See also:

rtc_get, rtc_reset

void rtc_reset

(

void

)

Reset the counter of the realtime clock.

Resets the real time clock counter to 0.

See also:

rtc_init, rtc_get