xtest09_2.c

来自「AT91sam7s 256 B/D example」· C语言 代码 · 共 53 行

/* ========================================================================== */
/*		Xtest09_2.c : PIT Interrupt Program(0.5Hz Speed)	      */
/* ========================================================================== */
/*			  Designed and programmed by Duck-Yong Yoon in 2007.  */

#include "AT91SAM7S256.h"
#include "lib_AT91SAM7S256.h"
#include "OK7S256ads.h"

volatile unsigned int PIT_count=0;		// PIT interrupt count
volatile unsigned int PIT_flag=0;		// PIT interrupt flag

void PIT_ISR(void)				/* PIT interrupt service routine */
{
  AT91F_PITGetPIVR(AT91C_BASE_PITC);		// clear PITS

  PIT_count++;					// increment PIT_count

  if(PIT_count < 10)				// 5Hz/10 = 0.5Hz
    return;

  PIT_count = 0;				// if PIT_count=10, clear it
  PIT_flag ^= 0x01;				// toggle PIT_flag

  if(PIT_flag == 1)				// if PIT_flag=1, LED2 on
    LED_on(LED2);
  else						// if PIT_flag=0, LED2 off
    LED_off(LED2);
}

int main(void)
{
  MCU_initialize();				// initialize AT91SAM7S256 & kit
  Delay_ms(50);					// wait for system stabilization
  LCD_initialize();				// initialize text LCD module

  LCD_string(0x80, " PIT Interrupt  ");		// display title
  LCD_string(0xC0, "    (0.5 Hz)    ");
  Beep();

  LED_off(LED2|LED1);				// LED2~LED1 off

  AT91F_PITC_CfgPMC();				// enable peripheral clock for PIT
  AT91F_PITInit(AT91C_BASE_PITC,1,48);		// enable and initialize PIT
  AT91F_PITSetPIV(AT91C_BASE_PITC,600000-1);	// 48MHz/16/600000 = 5Hz
  
  AT91F_PITEnableInt(AT91C_BASE_PITC);		// initialize PIT interrupt
  AT91F_AIC_ConfigureIt(AT91C_BASE_AIC,AT91C_ID_SYS,7,1,PIT_ISR);
  AT91F_AIC_EnableIt(AT91C_BASE_AIC,AT91C_ID_SYS);

  while(1);					// wait for interrupt
}