main.c

一个关于AVR单片机的例程

// ICC-AVR application builder : 2007-5-28 22:03:35
// Target : M16
// Crystal: 7.3728Mhz
// 连接：接好电源和晶振的跳线
// 7断数码管的ABCD接VCC，a~dp接PA0～PA7
#include <iom16v.h>
#include <macros.h>

const unsigned char seg7_data[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71,0x00};//0~F and "shut"
volatile  unsigned char i; //在中断中会变化的变量，加volatile限定词定义

void port_init(void)
{
 PORTA = 0x00;
 DDRA  = 0xFF;
 PORTB = 0x00;
 DDRB  = 0x00;
 PORTC = 0x00; //m103 output only
 DDRC  = 0x00;
 PORTD = 0x00;
 DDRD  = 0x00;
}

//TIMER1 initialize - prescale:256
// WGM: 0) Normal, TOP=0xFFFF
// desired value: 1Sec
// actual value:  1.000Sec (0.0%)
void timer1_init(void)
{
 TCCR1B = 0x00; //stop
 TCNT1H = 0x8F; //setup
 TCNT1L = 0x81;
 OCR1AH = 0x70;
 OCR1AL = 0x7F;
 OCR1BH = 0x70;
 OCR1BL = 0x7F;
 ICR1H  = 0x70;
 ICR1L  = 0x7F;
 TCCR1A = 0x00;
 TCCR1B = 0x04; //start Timer
}

#pragma interrupt_handler timer1_ovf_isr:iv_TIMER1_OVF
void timer1_ovf_isr(void)
{
 //TIMER1 has overflowed
 TCNT1H = 0x8F; //reload counter high value
 TCNT1L = 0x81; //reload counter low value
 i++;   //在文件开始的定义，volatile unsigned char i;
 if(i==10) i=0;
}

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

 MCUCR = 0x00;
 GICR  = 0x00;
 TIMSK = 0x04; //timer interrupt sources ,这里允许了timer1溢出中断。
 SEI(); //re-enable interrupts
 //all peripherals are now initialized
}

void main(void)
{
 init_devices(); //初始化，包含了定时器的初始化
 while(1)
 {
  PORTA=seg7_data[i]; //一直刷新显示计时
 }
}