单片机笔记---测量计算输入的脉冲宽度

最新推荐文章于 2022-01-30 21:29:56 发布

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最新推荐文章于 2022-01-30 21:29:56 发布

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分类专栏：基础电子电子测量文章标签： timer

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本文介绍了一个基于AVR单片机M128的程序设计，该程序利用定时器和输入捕捉功能来测量外部脉冲的宽度。通过配置定时器1并设置中断服务例程，实现了对外部脉冲上升沿和下降沿的捕获，并计算脉冲宽度。

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使能输入捕捉功能, 测量计算输入的脉冲宽度:

//ICC-AVR application builder : 2006-7-14 10:13:46
// Target : M128
// Crystal: 14.7456Mhz

#include <iom128v.h>
#include <macros.h>

//define PORT B as output for pulse width
#define pulse_out PORTB

//define ICP so we can read the pin
#define ICP PIND4

unsigned char ov_counter;
unsigned int  rising_edge, falling_edge;
unsigned long pulse_clocks;

void port_init(void)
{
PORTA = 0x00;
DDRA  = 0x00;
PORTB = 0xFF;
DDRB  = 0xFF;
PORTC = 0x00; //m103 output only
DDRC  = 0x00;
PORTE = 0x00;
DDRE  = 0x00;
PORTF = 0x00;
DDRF  = 0x00;
PORTG = 0x00;
DDRG  = 0x00;
}

//TIMER0 initialize - prescale:1024
// WGM: Normal
// desired value: 14.44444444KHz
// actual value: -0.001KHz (1444544.4%)
void timer1_init(void)
{
TCCR1B = 0xc4; //start timer 预分频为64
}

#pragma interrupt_handler timer1_ovf_isr:15
void timer1_ovf_isr(void)
{
  ov_counter++;
}

#pragma interrupt_handler timer1_capt_isr:13
void timer1_capt_isr(void)
{
if (ICP)
{
  rising_edge=ICR1;  //save start time for pulse
  TCCR1B&=0xBF; //set to trigger on falling edge next
  ov_counter=0;
}

else
{
  falling_edge =ICR1;
  TCCR1B|=0x40;
  pulse_clocks= (unsigned long) falling_edge - (unsigned long) rising_edge
                +(unsigned long) ov_counter*0x10000;
  pulse_out=pulse_clocks/230;
}
}


//call this routine to initialise all peripherals
void init_devices(void)
{
//stop errant interrupts until set up
CLI(); //disable all interrupts
XDIV  = 0x00; //xtal divider
XMCRA = 0x00; //external memory
port_init();

MCUCR = 0x00;
EICRA = 0x00; //extended ext ints
EICRB = 0x00; //extended ext ints
EIMSK = 0x00;
TIMSK = 0x00; //timer interrupt sources
ETIMSK = 0x00; //extended timer interrupt sources
SEI(); //re-enable interrupts
//all peripherals are now initialised
}

void main(void)
{
  port_init();
  init_devices();
  timer1_init();
  TIMSK=0x24;
  SEI();
  while(1)
  {
   ;
  }
}