请教：如何写PWM信号 - - Powered by Discuz!

/*---------------------------------------------------------------------*/
/* --- STC MCU Limited ------------------------------------------------*/
/* --- STC 1T Series MCU Demo Programme -------------------------------*/
/* 如果要在程序中使用此代码,请在程序中注明使用了STC的资料及程序 */
/*---------------------------------------------------------------------*/
/************* 功能说明 **************
使用Timer0模拟6通道PWM驱动程序。
输出为 P3.0 ~ P3.5, 对应 PWM0 ~ PWM5.
定时器中断频率一般不要超过100KHZ, 留足够的时间给别的程序运行.
本例子使用11.0592MHZ时钟, 25K的中断频率, 250级PWM, 周期为10ms.
中断里处理的时间不超过6us, 占CPU时间大约为15%.
******************************************/
//芯片是STC15F101W的
#include <reg52.h>
#define MAIN_Fosc 11059200UL //定义主时钟
#define Timer0_Rate 25000 //中断频率
typedef unsigned char u8;
typedef unsigned int u16;
typedef unsigned long u32;
sfr AUXR = 0x8E;
sfr P3M1 = 0xB1; //PxM1.n,PxM0.n =00--->Standard, 01--->push-pull
sfr P3M0 = 0xB2; // =10--->pure input, 11--->open drain
#define Timer0_Reload (65536UL -(MAIN_Fosc / Timer0_Rate)) //Timer 0 重装值
//************** PWM8 变量和常量以及IO口定义 ***************
//******************** 8通道8 bit 软PWM ********************
#define PWM_DUTY_MAX 250 // 0~255 PWM周期, 最大255
#define PWM_ON 1 // 定义占空比的电平, 1 或 0
#define PWM_OFF (!PWM_ON)
#define PWM_ALL_ON (0xff * PWM_ON)
u8 bdata PWM_temp1; //影射一个RAM，可位寻址，输出时同步刷新
sbit P_PWM0 = PWM_temp1^0; // 定义影射RAM每位对应的IO
sbit P_PWM1 = PWM_temp1^1;
sbit P_PWM2 = PWM_temp1^2;
sbit P_PWM3 = PWM_temp1^3;
sbit P_PWM4 = PWM_temp1^4;
sbit P_PWM5 = PWM_temp1^5;
u8 pwm_duty; //周期计数值
u8 pwm[6]; //pwm0~pwm5 为0至5路PWM的宽度值
bit B_1ms;
u8 cnt_1ms;
u8 cnt_20ms;
/**********************************************/
void main(void)
{
u8 i;
P3M0 = 0x00;
P3M1 = 0x00;
AUXR |= (1<<7); // Timer0 set as 1T mode
TMOD &= ~(1<<2); // Timer0 set as Timer
TMOD &= ~0x03; // Timer0 set as 16 bits Auto Reload
TH0 = Timer0_Reload / 256; //Timer0 Load
TL0 = Timer0_Reload % 256;
ET0 = 1; //Timer0 Interrupt Enable
PT0 = 1; //高优先级
TR0 = 1; //Timer0 Run
EA = 1; //打开总中断
cnt_1ms = Timer0_Rate / 1000; //1ms计数
cnt_20ms = 20;
for(i=0; i<6; i++) pwm[i] = i * 5 + 5; //给PWM一个初值
while(1)
{
if(B_1ms) //1ms到
{
B_1ms = 0;
if(--cnt_20ms == 0) //PWM 20ms改变一阶
{
cnt_20ms = 20;
for(i=0; i<6; i++) pwm[i]++;
}
}
}
}
/********************** Timer0 1ms中断函数 ************************/
void timer0 (void) interrupt 1
{
P3 = PWM_temp1; //影射RAM输出到实际的PWM端口
if(++pwm_duty == PWM_DUTY_MAX) //PWM周期结束，重新开始新的周期
{
pwm_duty = 0;
PWM_temp1 = PWM_ALL_ON;
}
ACC = pwm_duty;
if(ACC == pwm[0]) P_PWM0 = PWM_OFF; //判断PWM占空比是否结束
if(ACC == pwm[1]) P_PWM1 = PWM_OFF;
if(ACC == pwm[2]) P_PWM2 = PWM_OFF;
if(ACC == pwm[3]) P_PWM3 = PWM_OFF;
if(ACC == pwm[4]) P_PWM4 = PWM_OFF;
if(ACC == pwm[5]) P_PWM5 = PWM_OFF;
if(--cnt_1ms == 0)
{
cnt_1ms = Timer0_Rate / 1000;
B_1ms = 1; // 1ms标志
}
}

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