Time Keeping

Measuring Time with Millisecond Resolution. More...

Files
file	time.h
	Time API Header.
file	time.c
	Time API Implementation.

Macros
#define	TCRA   TCCR2A
	Timer 2 Control Register A. More...
#define	TCRB   TCCR2B
	Timer 2 Control Register B. More...
#define	OCR   OCR2A
	Timer 2 Compare Register A. More...
#define	TIMS   TIMSK2
	Timer 2 Interrupt Mask. More...
#define	OCIE   OCIE2A
	Timer 2 Compare Match A Interrupt Enable. More...

Typedefs
typedef uint64_t	time_t
	Timekeeping Data Type. More...

Functions
void	initSystemTimer (void)
	Initialize the system timer. More...
time_t	getSystemTime (void)
	Get the System Uptime. More...
	ISR (TIMER2_COMPA_vect)
	Timer 2 Compare Match A Interrupt. More...

Variables
volatile time_t	systemTime = 0
	Current System Uptime. More...

Detailed Description

Measuring Time with Millisecond Resolution.

Uses Timer 2

Prescaler 64

Count to 250

16000000 / 64 / 250 = 1000 –> 1 Interrupt per millisecond

Macro Definition Documentation

#define OCIE   OCIE2A

Timer 2 Compare Match A Interrupt Enable.

Definition at line 53 of file time.c.

#define OCR   OCR2A

Timer 2 Compare Register A.

Definition at line 51 of file time.c.

#define TCRA   TCCR2A

Timer 2 Control Register A.

Definition at line 49 of file time.c.

#define TCRB   TCCR2B

Timer 2 Control Register B.

Definition at line 50 of file time.c.

#define TIMS   TIMSK2

Timer 2 Interrupt Mask.

Definition at line 52 of file time.c.

Typedef Documentation

typedef uint64_t time_t

Timekeeping Data Type.

Overflows after 500 million years... :)

Definition at line 53 of file time.h.

Function Documentation

time_t getSystemTime

(

void

)

Get the System Uptime.

Returns

System Uptime in Milliseconds

Examples:

hardwareTest.c, and uartFlight.c.

Definition at line 68 of file time.c.

References systemTime.

Referenced by complementaryExecute(), complementaryInit(), orientationTask(), and pidExecute().

                           {
    return systemTime;
}

void initSystemTimer

(

void

)

Initialize the system timer.

Execution every millisecond. Uses Timer 2.

Definition at line 55 of file time.c.

Referenced by xyInit().

                       {
    // Timer initialization
    TCRA |= (1 << WGM21); // CTC Mode
    TCRB |= (1 << CS22); // Prescaler: 64
    OCR = 250;
    TIMS |= (1 << OCIE); // Enable compare match interrupt
}

ISR

(

TIMER2_COMPA_vect

)

Timer 2 Compare Match A Interrupt.

Definition at line 64 of file time.c.

References systemTime.

                       {
    systemTime++;
}

Variable Documentation

volatile time_t systemTime = 0

Current System Uptime.

Definition at line 47 of file time.c.

Referenced by getSystemTime(), and ISR().