单片机变频pwm实验程序设计与原理

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单片机变频pwm实验程序设计与原理

来源：本站整理作者：佚名 2011-12-16 06:31:05

昨晚给师弟讲课的内容，利用stc的一款单片机提供的PWM实现变频输出。程序将变频pwm输出到LED上作测试。

#include<reg52.h>

sfr   CCON   = 0xD8;
sfr   CMOD   = 0xD9;
sfr   CL     = 0xE9;
sfr   CH     = 0xF9;
sfr   CCAP0L = 0xEA;
sfr   CCAP0H = 0xFA;
sfr   CCAPM0 = 0xDA;
sfr   CCAPM1 = 0xDB;

sbit CR = 0xDE;
sbit led = P2^0;

unsigned char duty = 0x80;
unsigned int fre = 0xffff;

void timer0_int (void) interrupt 1 using 1
{
TH0 = fre >> 8;
TL0 = fre & 0xff;
led = ~led;
}

void timer0_init(void)
{
    TMOD &= 0xf0; /* Set timer 0 */
TMOD |= 0x1; /* mode 1 */
TH0 = 0xff;
TL0 = 0xff;
TR0 = 1; /* Enable timer 0 */
ET0 = 1; /* Enable timer 0 interrupt */
}

void pwm_init(void)
{
    CMOD = 0x4; // Use timer0
    CL = 0x0;
    CH = 0x0;
    CCAP0H = duty;   //Duty Cycle
    CCAPM0 = 0x42; // PWM mode
    CR = 1;   //Start PCA Timer.
}

void SOFt_delay(unsigned int _1ms)
{
unsigned int tmp;
while(_1ms--!=0) {
  for(tmp=0;tmp<144;tmp++);
}
}
void check_key(void)
{
unsigned char key1,key2;
key1 = P1 & 0xf;
soft_delay(20);
key2 = P1 & 0xf;

if(key1 == key2 && key1 != 0xf){
  if(key1 == 0xe)
   duty += 16;
  else if(key1 == 0xd)
   duty -= 16;
  else if(key1 == 0xb)
   fre += 0xff;
  else if(key1 == 0x7)
   fre -= 0xff;
  while((P1 & 0xf) != 0xf);
}
}