csbmain.c

超声波测距的一个实例代码。语言：C 单片机：atmega48 编译环境：iccavr ide 测量结果回传给PC

//ICC-AVR application builder : 2008-1-25 14:03:04
// Target : m48
// Crystal: 7.3728Mhz
//finish time 08/01/25

#include <iom48v.h>
#include <macros.h>
unsigned int count_sum;//计时值
unsigned char s_celiang,send_socr;
unsigned char buff[6]={0,0,0,'.',0,'M'};
unsigned long c_sum;

void port_init(void)
{
 PORTB = 0x00;//      __
 DDRB  = 0x02;//pb1__| |__
 PORTC = 0x00; //m103 output only
 DDRC  = 0x00;
 PORTD = 0x00;
 DDRD  = 0x00;
}

//TIMER0 initialize - prescale:1
// WGM: Normal
// desired value: 40KHz
// actual value: 40.070KHz (0.2%)
void timer0_init(void)
{
 TCCR0B = 0x00; //stop
 TCNT0 = 0xD2; //set count
 TCCR0A = 0x00; 
 TCCR0B = 0x02; //start timer
}

#pragma interrupt_handler timer0_ovf_isr:iv_TIM0_OVF
void timer0_ovf_isr(void)//波形产生
{
 //TIMER0 has overflowed
 PORTB = (~PORTB)&0x02;// 取反pb1电平
 TCNT0 = 0xD2; //set count
 //TCCR0B = 0x01; //start timer
}

void send_to_pc()//数据回传给PC
{ 
 unsigned char i;
 for(i=0;i<6;i++)
 {
 while ( !( UCSR0A & (1<<UDRE0)) );
 UDR0=buff[i];
 } 
}
//TIMER1 initialize - prescale:8
// WGM: 0) Normal, TOP=0xFFFF
// desired value: 1Hz
// actual value: Out of range
void timer1_init(void)
{
 TCCR1B = 0x00; //stop
 TCNT1H = 0x00 /*INVALID SETTING*/; //setup
 TCNT1L = 0x00 /*INVALID SETTING*/; 
 TCCR1A = 0x00;
  //start Timer
}

#pragma interrupt_handler timer1_ovf_isr:iv_TIM1_OVF
void timer1_ovf_isr(void)
{
 //TIMER1 has overflowed
 
 TCNT1H = 0x00 /*INVALID SETTING*/; //reload counter high value
 TCNT1L = 0x00 /*INVALID SETTING*/; //reload counter low value
}

//UART0 initialize
// desired baud rate: 9600
// actual: baud rate:9600 (0.0%)
// char size: 8 bit
// parity: Disabled
void uart0_init(void)
{
 UCSR0B = 0x00; //disable while setting baud rate
 UCSR0A = 0x00;
 UCSR0C = 0x06;
 UBRR0L = 0x2F; //set baud rate lo
 UBRR0H = 0x00; //set baud rate hi
 UCSR0B = 0x08;
}

#pragma interrupt_handler int0_isr:iv_INT0
void int0_isr(void)
{
 //external interupt on INT0
 s_celiang++;
 if(s_celiang==5) TCCR1B = 0x02;//启动计数
 if(s_celiang==6) 
 {
  TCCR0B = 0x00; //start timer
  TCCR1B = 0;//停止计数  
  count_sum=TCNT1;
  TCNT1=0;//清空计数
  s_celiang=0;
  send_socr=1;
  TCCR0B = 0x02; //start timer
 }
}

void mux_sum(unsigned long sum)//计算距离 
{
 unsigned long x; 
 x=sum/100;
 buff[0]=x+0x30;//百位
 x=sum%100/10;
 buff[1]=x+0x30;//十位
 x=(char) sum%100%10;
 buff[2]=x+0x30;//个位
 x=(char) sum*10%100%10;
 buff[4]=x+0x30;//小数
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 //stop errant interrupts until set up
 CLI(); //disable all interrupts
 port_init();
 timer0_init();
 timer1_init();
 uart0_init();

 MCUCR = 0x00;
 EICRA = 0x02; //extended ext ints
 EIMSK = 0x01;
 
 TIMSK0 = 0x01; //timer 0 interrupt sources
 TIMSK1 = 0x01; //timer 1 interrupt sources 
 
 PRR = 0x00; //power controller
 SEI(); //re-enable interrupts
 //all peripherals are now initialized
}

//
void main(void)
{
 
 init_devices();
 //insert your functional code here...
 while(1)
 {
  if(send_socr)
  {
   c_sum=count_sum;
   c_sum=(c_sum*340/2)/1000000;
   mux_sum(c_sum);
   send_to_pc();
   send_socr=0;
  }
 }
}