demo_11_1.c

AVR单片机嵌入式系统原理与应用实践例码

/*********************************************
File name			: demo_11_1.c
Chip type           : ATmega16
Program type        : Application
Clock frequency     : 4.000000 MHz
Memory model        : Small
External SRAM size  : 0
Data Stack size     : 256
*********************************************/

#include <mega16.h>
flash unsigned char led_7[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
flash unsigned char position[8]={0x7f,0xbf,0xdf,0xef,0xf7,0xfb,0xfd,0xfe};

unsigned char dis_buff[8];				// 显示缓冲区，存放要显示的8个字符的段码值
unsigned char posit;
bit	time_1ms_ok,display_ok=0;
unsigned char time0_old,time0_new,freq_time;
unsigned int freq;

void display(void)				// 8位LED数码管动态扫描函数
{
    PORTC = 0xff;
	PORTA = led_7[dis_buff[posit]];
	if (posit==5) PORTA = PORTA | 0x80; 
	PORTC = position[posit]; 
	if (++posit >=8 ) posit = 0;
}

// Timer 2 output compare interrupt service routine
interrupt [TIM2_COMP] void timer2_comp_isr(void)
{
	time0_new = TCNT0;			// 1ms到，记录当前T/C0的计数值
	time_1ms_ok = 1;
	display_ok = ~display_ok;
	if (display_ok) display();
}

void freq_to_disbuff(void)		// 将频率值转化为BCD码并送入显示缓冲区
{
	unsigned char i,j=7;
	for (i=0;i<=4;i++)
	{
		dis_buff[j-i] = freq % 10;
		freq = freq / 10;
	}
	dis_buff[2] = freq;
}

void main(void)
{
	unsigned char i;
    DDRA=0xFF;					// LED数码管驱动
    DDRC=0xFF;
	// T/C0初始化，外部计数方式
    TCCR0=0x06;					// 外部T0脚下降沿触发计数，普通模式
    TCNT0=0x00;
    OCR0=0x00;
	// T/C2初始化
    TCCR2=0x0B; 				// 内部时钟，32分频（4M/32=125KHz），CTC模式
    TCNT2=0x00;
    OCR2=0x7C;					// OCR2 = 0x7C(124),(124+1)/125=1ms

    TIMSK=0x80;	 				// 允许T/C2比较匹配中断

    for (i=0;i<=7;i++) dis_buff[i] = 0;
    time0_old = 0;

    #asm("sei")					// 开放全局中断

    while (1)
	{
    	if (time_1ms_ok)
    	{	// 累计T/C0的计数值
    		if (time0_new >= time0_old) freq = freq + (time0_new - time0_old);
    		else freq = freq + (256 - time0_old + time0_new);
    		time0_old = time0_new;
    		if (++freq_time >= 100)
    		{
    			freq_time = 0;			// 100ms到，
    			freq_to_disbuff();		// 将100ms内的脉冲计数值送显示
    			freq = 0;
    		} 
        		time_1ms_ok = 0;
    	}
	}
}