[AVR单片机] T0 输出的频率咋不准了呢

/*

LCD12864液晶屏显示实验。

PA1输出0.993KHz方波，通过PD6采集，并显示

*/



#include <iom16v.h>

#include "font.h"

#include "lcd12864.h"

#include <macros.h>

int contN;

unsigned char flow_flag=0; //用于标记定时器溢出,如果溢出了,只记录到TCNT的值就不对了哦,需要进行处理，应该是TOP*flow_flag+TCNT

unsigned int icpnum=0; //记录每次采集的TCNT差值,注意整个过程中不要操作TCNT,以免引入误差

unsigned char timerover_error=0;

unsigned int last_icrvalue=0; //记录上次的ICR值

unsigned int value;

void timer1_init(void)

{

TCCR1B = 0x00; //stop

TCNT1H = 0x00;

TCNT1L = 0x00;

ICR1H = 0x00;

ICR1L = 0x00;

TCCR1A = 0x00;

TCCR1B|=(1<<ICNC1)|(1<<ICES1)|(1<<CS11)|(1<<CS10); 

}



#pragma interrupt_handler timer1_capt_isr:12

void timer1_capt_isr(void)

{

PORTA|=(1<<7);

//CLI(); 

value=ICR1L; 

value|=(int)ICR1H << 8; 



if(flow_flag==0)

{

icpnum=value-last_icrvalue;

}

else

{

if(flow_flag==1)

{

flow_flag=0;

icpnum=0xFFFF-last_icrvalue+value;

}

else

{

timerover_error=1;

flow_flag=0;

}

}

last_icrvalue=value;

SEI(); 

}



void timer0_init(void)

{



TCCR0 = 0x00;

TCNT0 = 0xc6;

OCR0 = 0xc6;



TIMSK |= 0x03;



TCCR0 |=0B00011;

}





void init_devices(void)

{

CLI(); 

MCUCR = 0x00;

MCUCSR = 0x80;//禁止JTAG

GICR = 0x00;



DDRA |= (1<<PA1);

DDRD &=~ (1<<PD6);

PORTD |= (1<<PD6); 



timer0_init();

timer1_init(); //定时器1初始化

SEI();//开全局中断

}



//T0比较中断服务程序

#pragma interrupt_handler timer0_comp_isr:20

void timer0_comp_isr(void)

{

TCNT0 = 0xc6;

PORTA^=BIT(1);//

PORTD^=BIT(0);//

contN++;

}



//led show

void LCD_init(void)

{

DDRB = 0xFF; 

DDRC |= (1<<PC7)|(1<<PC6);//0xC0;

DDRD |= (1<<PD7)|(1<<PD6);//0xD0;



PORTC |=(1<< PC6);// 0x40;

PORTD |= (1<< PD6);//0x40;

PORTD &= ~(1<<PD7);//~0x80;

}

void displaynum(unsigned char row,int aa)

{ int at;

unsigned char asi1,n;



at=aa;n=1;

while(at>0)

{

asi1=at%10+48;

at/=10;

disp_charNum((16-n)*8+1,row,asi1);

n=n+1;

}

}



void main(void) 

{

unsigned int showN;

float Freque_value=0.00,T=0.00;//带小数位，精确度高

unsigned int Freque=0,t=0; //只显示整数，精确度低

unsigned int temp=0;



init_devices();

disp_init();

DDRA |=(1<<7) ;

PORTA &=~(1<< PA7);

DDRD |=(1<<0) ;

//PORTD &=~(1<< PA0);



disp_clear(0, 128, 0);

disp_clear(0, 128, 2);

disp_clear(0, 128, 4);

disp_clear(0, 128, 6);



while (1)

{

if(timerover_error==1)

{

//错误处理程序

}

temp = icpnum; 

Freque_value=(float)((float)1000000/(float)temp); 

//Freque=1000000/temp; 

T = (float)((float)temp/(float)1000); 

//t=temp/1000; 

displaynum(5,Freque_value);//LCD 显示数值

}





}