10-PWM脉宽调制信号的发生与控制

PWM脉冲调制信号的发生与控制

1、代码思路：

（1）我们可以利用定时器规定周期为10ms（100HZ），通过调节高电平时间来产生想要的PWM波，不同的亮度对应着不同占空比。

（2）首先我们先通过定时器产生四种不同的亮度，然后编写可以转换四种不同状态的按键，走后把他们整合起来

#include <REGX52.H>
sbit L1 = P0^0;
sbit S7 = P3^0;
unsigned char count = 0;
unsigned char pwm_duty = 0;
void Delay(unsigned int t) {

	
	while(t--);
}

void _74HC138(unsigned char n) {
	
	switch(n) {
		case 4:	P2 = (P2 & 0x1f) | 0x80;
		break;
		case 5:	P2 = (P2 & 0x1f) | 0xa0;
		break;
		case 6:	P2 = (P2 & 0x1f) | 0xc0;
		break;
		case 7:	P2 = (P2 & 0x1f) | 0xe0;
		break;
	
	}

}  
void sysInit(void) {
	_74HC138(5);
	P0 = 0x00;
	_74HC138(4);
	P0 = 0xFF;
}


void Timer0Init(void) {
	
	TMOD = 0x02;
	// 100us 
	TH0 = 256 - 100;
	TL0 = 256 - 100;
	EA = 1;
	ET0 = 1;
	
	// TR0 = 1;
	

}
unsigned char state = 0;
void Scan_Key(void) {
	
	if(S7 == 0) {
		Delay(300);
		if(S7 == 0) {
			
			
			switch(state) {
				case 0:
					TR0 = 1;   // 开启定时器
					L1 = 0;
					pwm_duty = 10;
					state = 1;
					break;
				case 1:
					pwm_duty = 50;
					state = 2;
					break;
				case 2:
					
					pwm_duty = 90;
					state = 3;
					break;
				case 3:
					
					L1 = 1;
					state = 0;
					TR0 = 0;
					
					break;
			
			}
			
			while(S7 == 0);
			
		
		}
	}

}


void Timer0Rountine () interrupt 1 {
	count++;
	// 20      20
	if(count == pwm_duty) {
		// 即对占空比的切换
		L1 = 1;            // count == pwm_duty 由低电平置为高电平
		
	}else if(count == 100) {
		L1 = 0;
		count= 0;
	}
	
	
}
void main(void) {
	sysInit(); 
	_74HC138(4);
	// 默认关灯
	L1 = 1;
	Timer0Init();
	while(1) {
		Scan_Key();
	}
	

	
	
	
}