单片机PWM程序是怎么编写的啊，能给一个简单的例子吗？

有PWM功能的单片机入STC12系列单片机，直接给专用寄存器赋值开启相应定时器就可以了。普通单单片机，PWM需要用自己来调配。比如：

#include<reg51.h>

unsigned char pwhh,pwhl,pwlh,pwll

bit flag

sbit pwm=P1^0

void t0isr() interrupt 1

{

if(flag)

{

TH0=pwhh

TL0=pwhl

}

else

{

TH0=pwlh

TL0=pwll

}

pwm=~pwm

}

main()

{

TMOD=0x01

pwhh=(65536-1000)/256

pwhl=(65536-1000)%256

pwlh=(65536-500)/256

pwll=(65536-500)%256

TH0=pwhh

L0=pwhl

TR0=1

ET0=1

EA=1

while(1)

}

#include <intrins.h>

#include <stdio.h>

#include <math.h>

#include "UPSD3200.H"

#include "upsd_pwm.h"

#define uint unsigned int

#define uchar unsigned char

PSD_REGS PSD8xx_reg _at_ csiop

#define KEYIO (~(PSD8xx_reg.DATAIN_A)) &0x07

sbit CP=P4^7

sbit U_D=P1^1

void init_system()// 系统初始化

uchar keyboard()

void uPSD_PWM4_Variable(unsigned char PWM_Period, unsigned char PWM_PulseWidth)

uchar Adjust_station=NO

unsigned char data x,flag

unsigned char keyboard() //键盘输入

{

unsigned char a=0xff,b=0x01,c=0xf8,d//有按键的位置

uint i

do{

a=KEYIO|c

}while(a==0xff)

if (a == 0xfe){d = '1'}

else if (a == 0xfd){d = '2'}

else if (a == 0xfb){d = '3'}

else {d = '0'}

return(d)

}

void uPSD_PWM4_Init(void)

unsigned int PWM_prescaler

P4SFS |= 0x80

PWM_prescaler = (unsigned int)((FREQ_OSC/2)/PWM4_INPUT_freq)//PWM4输入脉冲频率 K

PSCL1L = PWM_prescaler &0x00ff

PSCL1H = (PWM_prescaler >>8)

}

void StepMotor_GO(bit direction,uint speed) {

unsigned char PWM_Period, PWM_PulseWidth

uint temp_uint

U_D = direction//方向

temp_uint = (PWM4_INPUT_freq*1000)/speed

PWM_Period = (unsigned char)temp_uint

PWM_PulseWidth = PWM_Period/2

uPSD_PWM4_Variable(PWM_Period,PWM_PulseWidth)

}

void StepMotor_STOP(void)

{

P4SFS &= 0x7f

}

void uPSD_PWM4_Variable(unsigned char PWM_Period, unsigned char PWM_PulseWidth)

{

P4SFS |= 0x80

PWMVP = PWM_Period

PWMVPW = PWM_PulseWidth

PWMCON |= 0x20

}

void initkey(void){

PSD8xx_reg.DATAOUT_A=0xFF

PSD8xx_reg.CONTROL_A=0x00

PSD8xx_reg.DIRECTION_A=0x00

}

void init_system() // 系统初始化

{

WDKEY=0x55

P4SFS = (unsigned char) (0x08 <<3)

uPSD_PWM_Channel_8bit(3,243)

问题补充：(接着上面的序)

void uPSD_PWM_Init_8bit(unsigned char PWM_channel_no, unsigned int PWM_freq8, unsigned char PWMCON_value)

{

unsigned int PWM_prescaler

unsigned char output_polarity_mode

output_polarity_mode = PWMCON_value &0x8F

PWMCON = (PWMCON &0x70) | output_polarity_mode

P4SFS = (unsigned char) (0x08 <<PWM_channel_no)

PWM_prescaler = (unsigned int) ( (((unsigned int) FREQ_OSC) / 2) / PWM_freq8)

PSCL0L = PWM_prescaler &0x00ff

PSCL0H = (PWM_prescaler >>8)

PSCL1L = PWM_prescaler &0x00ff

PSCL1H = (PWM_prescaler >>8)

}

void uPSD_PWM_Disable(void)

{

PWMCON &= 0xDF

}

void main(void){

x=0

init_system()

flag=1

while(flag==1){

x=keyboard()

if(x=='1') {StepMotor_GO(0,100)}

else if(x=='2') {StepMotor_GO(1,500)}

else if(x=='3') { StepMotor_STOP()uPSD_PWM_Disable()}

else if(x=='0') {uPSD_PWM_Disable()}

}

}

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