timer1._c

用的avr icc 开发的atmega16的超声波测距仪模型。

#define TIMER1_C
#include "includes.h"
 //TIMER1 initialisation - prescale:64
// WGM: 0) Normal, TOP=0xFFFF
// desired value: 200000uSec
// actual value: 200000.000uSec (0.0%)
unsigned char cap[4]={0,};
void timer1_init(void)
{
 TCCR1B = 0x00; //stop
 TCNT1H = 0xCF; //setup 200 000 uSec
 TCNT1L = 0x2C;
 OCR1AH = 0x30;
 OCR1AL = 0xD4;
 OCR1BH = 0x30;
 OCR1BL = 0xD4;
 ICR1H  = 0x30;
 ICR1L  = 0xD4;
 TCCR1A = 0x00;
                //TCCR1B = 0xC3; //start Timer
}

#pragma interrupt_handler timer1_capt_isr:6
void timer1_capt_isr(void)
{ 
 //timer 1 input capture event, read (int)value in ICR1 using;
  capt_timer1=ICR1L;            //Read low byte first (important)
  capt_timer1|=(int)ICR1H << 8; //Read high byte and shift into top byte
  timer1_stop();//stop timer1
  TIMSK = 0x00; //disable capt interupt
  TCNT1H = 0xCF /*INVALID SETTING*/; //reload counter high value
  TCNT1L = 0x2C /*INVALID SETTING*/; //reload counter low value
                              
  capt_timer1=capt_timer1-0xcf2c;//DATA SIGNIAL PROCESSING
  capt_timer1=(capt_timer1/625)*speed/100/2.55;//DATA SIGNIAL PROCESSING
  cap[3]='0'+capt_timer1/1000;
  capt_timer1%=1000;
  cap[2]='0'+capt_timer1/100;
  capt_timer1%=100;
  cap[1]='0'+capt_timer1/10;
  capt_timer1%=10;
  cap[0]='0'+capt_timer1;
   LCD_DisplayString(2,1,"LENTH= ");
   LCD_Cursor (2,8);
   LCD_DisplayCharacter (cap[3]);
   LCD_Cursor (2,9);
   LCD_DisplayCharacter (cap[2]);
   LCD_Cursor (2,10);
   LCD_DisplayCharacter (cap[1]);
   LCD_Cursor (2,11);
   LCD_DisplayCharacter ('.');
   LCD_Cursor (2,12);
   LCD_DisplayCharacter (cap[0]);
   LCD_DisplayString(2,13,"m     ");
}

#pragma interrupt_handler timer1_ovf_isr:9
void timer1_ovf_isr(void)
{
 //TIMER1 has overflowed
 timer1_stop();
 TIMSK = 0x00; //disable ovf interupt
 TCNT1H = 0xCF /*INVALID SETTING*/; //reload counter high value
 TCNT1L = 0x2C /*INVALID SETTING*/; //reload counter low value
 LCD_DisplayString(2,1,"OUT OF RANGE !");//(ROW(1-2),COLUMN(1-16),STRING)
}

void timer1_start(void)
  {TCCR1B = 0x00;//STOP TIMER1
   TCNT1H = 0xCF;//200 000 us
   TCNT1L = 0x2C ;
   TCCR1B = 0xC3; 
  }
void timer1_stop(void)
  {
   TCCR1B=0x00;//STOP TIMER1
  }