demo_11_3.i

基于AVR单片机捕捉功能实现高精度的周期测量.原理就是将被测信号作为ICP1的输入,被测信号的上升(下降)沿作为输入捕捉的触发信号.捕捉事件发生的时间印记由硬件自动 同步复制到ICR1中,因此所得到

/*********************************************
File name	        : demo_11_3.c
Chip type           : ATmega16
Program type        : Application
Clock frequency     : 4.000000 MHz
Memory model        : Small
External SRAM size  : 0
Data Stack size     : 256
*********************************************/

// CodeVisionAVR C Compiler
// (C) 1998-2001 Pavel Haiduc, HP InfoTech S.R.L.

// I/O registers definitions for the ATmega16


#pragma used+
sfrb TWBR=0;
sfrb TWSR=1;
sfrb TWAR=2;
sfrb TWDR=3;
sfrb ADCL=4;
sfrb ADCH=5;
sfrw ADCW=4;      // 16 bit access
sfrb ADCSRA=6;
sfrb ADMUX=7;
sfrb ACSR=8;
sfrb UBRRL=9;
sfrb UCSRB=0xa;
sfrb UCSRA=0xb;
sfrb UDR=0xc;
sfrb SPCR=0xd;
sfrb SPSR=0xe;
sfrb SPDR=0xf;
sfrb PIND=0x10;
sfrb DDRD=0x11;
sfrb PORTD=0x12;
sfrb PINC=0x13;
sfrb DDRC=0x14;
sfrb PORTC=0x15;
sfrb PINB=0x16;
sfrb DDRB=0x17;
sfrb PORTB=0x18;
sfrb PINA=0x19;
sfrb DDRA=0x1a;
sfrb PORTA=0x1b;
sfrb EECR=0x1c;
sfrb EEDR=0x1d;
sfrb EEARL=0x1e;
sfrb EEARH=0x1f;
sfrw EEAR=0x1e;   // 16 bit access
sfrb UBRRH=0x20;
sfrb UCSRC=0X20;
sfrb WDTCR=0x21;
sfrb ASSR=0x22;
sfrb OCR2=0x23;
sfrb TCNT2=0x24;
sfrb TCCR2=0x25;
sfrb ICR1L=0x26;
sfrb ICR1H=0x27;
sfrb OCR1BL=0x28;
sfrb OCR1BH=0x29;
sfrw OCR1B=0x28;  // 16 bit access
sfrb OCR1AL=0x2a;
sfrb OCR1AH=0x2b;
sfrw OCR1A=0x2a;  // 16 bit access
sfrb TCNT1L=0x2c;
sfrb TCNT1H=0x2d;
sfrw TCNT1=0x2c;  // 16 bit access
sfrb TCCR1B=0x2e;
sfrb TCCR1A=0x2f;
sfrb SFIOR=0x30;
sfrb OSCCAL=0x31;
sfrb OCDR=0x31;
sfrb TCNT0=0x32;
sfrb TCCR0=0x33;
sfrb MCUCSR=0x34;
sfrb MCUCR=0x35;
sfrb TWCR=0x36;
sfrb SPMCR=0x37;
sfrb TIFR=0x38;
sfrb TIMSK=0x39;
sfrb GIFR=0x3a;
sfrb GICR=0x3b;
sfrb OCR0=0X3c;
sfrb SPL=0x3d;
sfrb SPH=0x3e;
sfrb SREG=0x3f;
#pragma used-

// Interrupt vectors definitions


// Needed by the power management functions (sleep.h)
#asm
	#ifndef __SLEEP_DEFINED__
	#define __SLEEP_DEFINED__
	.EQU __se_bit=0x40
	.EQU __sm_mask=0xB0
	.EQU __sm_powerdown=0x20
	.EQU __sm_powersave=0x30
	.EQU __sm_standby=0xA0
	.EQU __sm_ext_standby=0xB0
	.EQU __sm_adc_noise_red=0x10
	.SET power_ctrl_reg=mcucr
	#endif
#endasm



sfrw ICR1=0x26;        // 补充定义16位寄存器ICR1地址为0x26(mega16.h中未定义)

flash unsigned char led_7[11]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x00}; 
flash unsigned char position[6]={0xfe,0xfd,0xfb,0xf7,0xef,0xdf};

unsigned char dis_buff[6];					// 显示缓冲区，存放要显示的6个字符的段码值
unsigned int icp_v1,icp_v2;
unsigned char icp_n,max_icp;
bit icp_ok,time_4ms_ok,f_2_d,begin_m,full_ok;

void display(void)					// 6位LED数管动态扫描函数
{
    static unsigned char posit;
	PORTC = 0xff;
	PORTA = led_7[dis_buff[posit]];
	PORTC = position[posit]; 
	if (++posit == 6) posit = 0;
}

// Timer 2 比较匹配中断服务，4ms定时 
interrupt [4] void timer2_comp_isr(void)
{
 	#asm("sei")			// 开放全局中断,允许中断嵌套   
    display();
    time_4ms_ok = 1;
}

// Timer 1 溢出中断服务
interrupt [9] void timer1_ovf_isr(void)
{
    full_ok = 1;
}

// Timer 1 输入捕捉中断服务
interrupt [6] void timer1_capt_isr(void)
{
    if (icp_n >= max_icp)   // 第N个上升沿到
    {
        icp_v2 = ICR1;      // 记录第N个上升沿时间
        TIMSK = 0x80;       // 禁止T/CI输入捕捉和溢出中断
        icp_ok = 1;
    }
    else if (icp_n == 0)
    {
        icp_v1 = ICR1;      // 记录第1个上升沿时间
    }    
    icp_n++;     
}

void f_to_disbuf(long v)	// 频率值送显示缓冲区函数
{
	unsigned char i;
	for (i=0;i<=4;i++)
	{
        dis_buff[i] = v%10;
        v /= 10; 
	}
	dis_buff[5] = v;
	for (i=5;i>0;i--)       // 高位零不显示
	{
	    if (dis_buff[i] == 0)
	        dis_buff[i] = 10;
	    else
	        break;    
	}
}

void main(void)
{
    unsigned int icp_1,icp_2;
    long fv;
    
	DDRA=0xFF;          // LED段码输出
	PORTC=0xFF;
	DDRC=0x3F;          // LED位控输出
	PORTD=0x40;         // PD6(icp)输入方式，上拉有效

    // T/C2 初始化
    TCCR2=0x0C;         // 内部时钟，64分频（4M/64=62.5KHz），CTC模式
    OCR2=0xf9;//7c;          // OCR2 = 0xf9(249),(249+1)/62.5=4ms
 	// T/C1初始化
    TCCR1B = 0x41;      // T/C1正常计数方式，上升沿触发输入捕捉，4M/1计数时钟
	TIMSK = 0xA4;		// 允许T/C2比较匹配中断，允许T/C1输入捕捉、溢出中断

    icp_n = 0;
    max_icp =1;
  	#asm("sei")			// 开放全局中断

	while (1)
	{
	    if (icp_ok == 1)    // 完成一次测量
	    {
	        if (icp_v2 >= icp_v1)          // 计算N个上升沿的时钟脉冲个数，
	            icp_2 = icp_v2 - icp_v1;   
	        else
	            icp_2 = 65536 - icp_v1 + icp_v2;
	        
	        if (!(icp_v2 >= icp_v1 && full_ok)) // 有溢出，数据无效    
            {           
                if (icp_2 == icp_1)         // 两次个数相等，测量有效 
	            {
                    fv = 4000000 * (long)max_icp / icp_2;     // 换算成频率值
                    f_2_d = 1;              // 允许新频率送显示
                
                    if (fv > 4000)
                        max_icp = 64;       // 如果频率大于4Khz，N=64
                    else
                        max_icp = 1;        // N=1
                 }
	        }
	        else
	            max_icp = 1;    // 有溢出，N=1
         
	        icp_1 = icp_2;          
	        icp_ok = 0;
            begin_m = 1;
  	    }
	    if (time_4ms_ok)            
	    {                           
	        if (f_2_d)
	        {
	            f_to_disbuf(fv);   // 新频率送显示
	            f_2_d = 0;
	        }
	        else if (begin_m)          
	        {
                icp_n = 0;      // 开始新的一次测量，
                full_ok = 0;    // 清除溢出标志
	            TIFR = 0x24;    // 清除可能存在的输入捕捉、溢出中断标志位
	            TIMSK = 0xa4;	// 开启T/C1输入捕捉、溢出中断允许        
	            begin_m = 0;
	        }
            time_4ms_ok = 0;	    
	    }
    }
}