(转)Cortex-M3 (NXP LPC1788)之PWM

PWM即脉宽调制，可用于输出一定占空比的方波。LPC1788有两个PWM,每个PWM可以由6路的输出，PWM1~PWM6。下面介绍使用PWM0.1输出PWM波。

        1，PWM使用公共的PCLK，因此要配置系统时钟和外设时钟。之前的文章中有具体的时钟配置过程。

        2，使能PWM模块。配置外设功率配置寄存器PCONP，使能PWM0的时钟控制位。

        3，PWM0.1的输出管脚和P1_2管脚复用，因此要配置IOCON_P1_02寄存器，将其设置成PWM0.1的输出。

        4，设置PWM的脉冲宽度，基本的原理就是比较PWM定时器计数器TC和匹配寄存器MR中的值，如果匹配我们可以通过匹配控制寄存器MCR选择操作，如产生一个中断，复位TC，停止TC和预分频计数器PC且停止计数。匹配寄存器MR0通过在匹配是将计数器TC复位来控制PWM的周期频率。另一个匹配寄存器控制PWM沿的位置。如PWM0.1的输出，将使用MR0控制PWM的周期频率，MR1控制边沿的位置。

        5，最后是对于PWM的具体控制，配置PWM预分频寄存器PWMPR，该32位寄存器规定了PWM预分频计数的最大值，PWM预分频计数器寄存器PWMPC在每个PCLK上递增一次，当PWMPC和PWMPR值相等时,PWMTC的值会递增，而PWMPR在系一个PCLK周期被复位。这样，当PWMPR=0时，PWMTC会在每个PCLK上递增，而当PWMPR=1时，在每2个PCLK上递增。匹配寄存器PWMMR中的值和PWMTC的值比较，如果相等则触发在PWMMCR中配置的操作。当MR0和TC相等时，我们进行复位TC从新计数从而固定了PWM的周期频率。当定时器处于PWM模式时，软件对PWM匹配寄存器MR的写操作，写入值实际上被保存在一个映像寄存器中，不会被立即使用。所以在我们需要操作PWM锁存使能寄存器PWMLER，典型序列为：将新值写入MR，写PWMLER中相应的位，更改的MR值将在下一次定时器复位时生效。

        在下面的程序中，将给MR1中写入不同的匹配值，来控制PWM的占空比。为了方便使用LED灯进行示意。

 

[cpp] view plaincopyprint?
  1. #define CCLK        120000000 
  2. #define PCLK         60000000 
  3.  
  4. #define rFIO1DIR    (*(volatile unsigned*)(0x20098020)) 
  5. #define rFIO1MASK   (*(volatile unsigned*)(0x20098030)) 
  6. #define rFIO1PIN    (*(volatile unsigned*)(0x20098034)) 
  7. #define rFIO1SET    (*(volatile unsigned*)(0x20098038)) 
  8. #define rFIO1CLR    (*(volatile unsigned*)(0x2009803c)) 
  9.  
  10. #define rCLKSRCSEL  (*(volatile unsigned *)(0x400FC10C))     //时钟源选择寄存器   
  11. #define rPLL0CON    (*(volatile unsigned *)(0x400FC080))     //PLL0控制寄存器   
  12. #define rPLL0CFG    (*(volatile unsigned *)(0x400FC084))     //PLL0配置寄存器   
  13. #define rPLL0STAT   (*(volatile unsigned *)(0x400FC088))     //PLL0状态寄存器   
  14. #define rPLL0FEED   (*(volatile unsigned *)(0x400FC08C))     //PLL0馈送寄存器   
  15. #define rPLL1CON    (*(volatile unsigned *)(0x400FC0A0))        
  16. #define rPLL1CFG    (*(volatile unsigned *)(0x400FC0A4))   
  17. #define rPLL1STAT   (*(volatile unsigned *)(0x400FC0A8))   
  18. #define rPLL1FEED   (*(volatile unsigned *)(0x400FC0AC))   
  19. #define rCCLKSEL    (*(volatile unsigned *)(0x400FC104))     //CPU时钟选择寄存器   
  20. #define rUSBCLKSEL  (*(volatile unsigned *)(0x400FC108))     //USB时钟选择寄存器   
  21. #define rPCLKSEL    (*(volatile unsigned *)(0x400FC1A8))     //外设时钟寄存器   
  22. #define rPCON       (*(volatile unsigned *)(0x400FC0C0))   
  23. #define rPXCONP     (*(volatile unsigned *)(0x400FC0C4))   
  24. #define rSCS        (*(volatile unsigned *)(0x400FC1A0))     //系统控制和状态寄存器   
  25. #define rCLKOUTCFG  (*(volatile unsigned *)(0x400FC1C8)) 
  26.  
  27. #define rIOCON_P1_02    (*(volatile unsigned *)(0x4002C088)) 
  28. #define rPCONP      (*(volatile unsigned *)(0x400FC0C4)) 
  29.  
  30. #define rPWM0IR     (*(volatile unsigned *)(0x40014000)) 
  31. #define rPWM0TCR    (*(volatile unsigned *)(0x40014004)) 
  32. #define rPWM0TC     (*(volatile unsigned *)(0x40014008)) 
  33. #define rPWM0PR     (*(volatile unsigned *)(0x4001400C)) 
  34. #define rPWM0CTCR   (*(volatile unsigned *)(0x40014070)) 
  35. #define rPWM0MCR    (*(volatile unsigned *)(0x40014014)) 
  36. #define rPWM0MR0    (*(volatile unsigned *)(0x40014018)) 
  37. #define rPWM0MR1    (*(volatile unsigned *)(0x4001401C)) 
  38. #define rPWM0CCR    (*(volatile unsigned *)(0x40014028)) 
  39. #define rPWM0PCR    (*(volatile unsigned *)(0x4001404C)) 
  40. #define rPWM0LER    (*(volatile unsigned *)(0x40014050)) 
  41.  
  42. #define rISER1      (*(volatile unsigned *)(0xE000E104)) 
  43. #define rCER1       (*(volatile unsigned *)(0xE000E184)) 
  44.  
  45. unsigned int duty = 10; 
  46. unsigned char match_cnt = 0; 
  47.  
  48. void PWM0_IRQHandler(void) 
  49. { 
  50.     if(rPWM0IR&0x1) 
  51.     { 
  52.         rFIO1PIN |= (1<<18); 
  53.         match_cnt++; 
  54.         rPWM0IR |= 0x1;     //MR0中断复位 
  55.     } 
  56.      
  57.     if(rPWM0IR&(0x1<<1)) 
  58.     { 
  59.         rFIO1PIN &= ~(1<<18); 
  60.         rPWM0IR |= 0x1<<1;  //MR1中断复位 
  61.     } 
  62. } 
  63.  
  64. void SystemInit()   
  65. {   
  66.     rSCS &= ~(0x1<<4);                //频率12M   
  67.     rSCS |= (0x1<<5);             //使能主振荡器   
  68.     while(0 == (rSCS & (0x1<<6)));//等待主振荡器稳定   
  69.        
  70.     rCLKSRCSEL = 0x1;   
  71.        
  72.     rPLL0CFG = 0x9;                 //配置CCLK = 120M   
  73.     rPLL0CON = 0x01;   
  74.     rPLL0FEED = 0xAA;   
  75.     rPLL0FEED =0x55;   
  76.     while( 0 == (rPLL0STAT & (0x1<<10)));    
  77.        
  78.     rCCLKSEL = (0x1 | (0x1<<8));   
  79.     rPCLKSEL = 0x2;                 //配置PCLK = 60M   
  80.        
  81.     rCLKOUTCFG = 0x0 | (0xb<<4) | (0x1<<8);   
  82. }  
  83.  
  84.  
  85. void PWMInit() 
  86. { 
  87.     rIOCON_P1_02 &= ~0x7; 
  88.     rIOCON_P1_02 |= 0x3;    //P1.02配置成PWM0[1] 
  89.      
  90.     rPCONP |= 0x1<<5;     //使能PWM0外设 
  91.      
  92.     rPWM0IR = 0x73F;    //初始化PWM相关控制寄存器 
  93.     rPWM0TCR = 0; 
  94.     rPWM0CTCR = 0; 
  95.     rPWM0MCR = 0; 
  96.     rPWM0CCR = 0; 
  97.     rPWM0PCR = 0; 
  98.     rPWM0LER = 0; 
  99.      
  100.     rPWM0PR = 0x1<<20;    //每0x1<<20+1个PLCK上升沿，TC递增 
  101.     rPWM0TCR |= 0x1<<1;   //复位TC和PC 
  102.     rPWM0TCR &= ~(0x1<<1); 
  103.      
  104.     rPWM0MR0 = 100; 
  105.     rPWM0LER |= 0x1; 
  106.     rPWM0MCR |= 0x1<<1 | 0x1;     //MR0和TC匹配时复位TC和PC.并且产生中断 
  107.      
  108.     rPWM0MR1 = duty; 
  109.     rPWM0LER |= 0x1<<1; 
  110.     rPWM0MCR |= 0x1<<3;   //MR1和TC匹配时产生中断 
  111. } 
  112.  
  113. int main () 
  114. { 
  115.     PWMInit(); 
  116.      
  117.     rFIO1DIR |= (0x1<<18); 
  118.     rISER1 |= 0x1<<7; //PWM0中断使能 
  119.      
  120.     rPWM0TCR |= 0x1<<1;   //复位TC和PC 
  121.     rPWM0TCR &= ~(0x1<<1); 
  122.      
  123.     rPWM0TCR |= 0x1;    //PC和TC计数使能 
  124.     rPWM0TCR |= 0x1<<3; //PWM模式使能 
  125.      
  126.     while(1) 
  127.     { 
  128.         if(match_cnt >= 1) 
  129.         { 
  130.             match_cnt = 0; 
  131.             duty = duty+10; 
  132.             if(duty >= 100) 
  133.             { 
  134.                 duty  = 0; 
  135.             } 
  136.             rPWM0MR1 = duty; 
  137.             rPWM0LER |= 0x1<<1; 
  138.             rPWM0MCR |= 0x1<<3; 
  139.         } 
  140.     } 
  141.     return 1; 
  142. }  
#define CCLK		120000000
#define PCLK		 60000000

#define rFIO1DIR	(*(volatile unsigned*)(0x20098020))
#define rFIO1MASK 	(*(volatile unsigned*)(0x20098030))
#define rFIO1PIN	(*(volatile unsigned*)(0x20098034))
#define rFIO1SET	(*(volatile unsigned*)(0x20098038))
#define rFIO1CLR	(*(volatile unsigned*)(0x2009803c))

#define rCLKSRCSEL  (*(volatile unsigned *)(0x400FC10C))     //时钟源选择寄存器  
#define rPLL0CON    (*(volatile unsigned *)(0x400FC080))     //PLL0控制寄存器  
#define rPLL0CFG    (*(volatile unsigned *)(0x400FC084))     //PLL0配置寄存器  
#define rPLL0STAT   (*(volatile unsigned *)(0x400FC088))     //PLL0状态寄存器  
#define rPLL0FEED   (*(volatile unsigned *)(0x400FC08C))     //PLL0馈送寄存器  
#define rPLL1CON    (*(volatile unsigned *)(0x400FC0A0))       
#define rPLL1CFG    (*(volatile unsigned *)(0x400FC0A4))  
#define rPLL1STAT   (*(volatile unsigned *)(0x400FC0A8))  
#define rPLL1FEED   (*(volatile unsigned *)(0x400FC0AC))  
#define rCCLKSEL    (*(volatile unsigned *)(0x400FC104))     //CPU时钟选择寄存器  
#define rUSBCLKSEL  (*(volatile unsigned *)(0x400FC108))     //USB时钟选择寄存器  
#define rPCLKSEL    (*(volatile unsigned *)(0x400FC1A8))     //外设时钟寄存器  
#define rPCON       (*(volatile unsigned *)(0x400FC0C0))  
#define rPXCONP     (*(volatile unsigned *)(0x400FC0C4))  
#define rSCS        (*(volatile unsigned *)(0x400FC1A0))     //系统控制和状态寄存器  
#define rCLKOUTCFG  (*(volatile unsigned *)(0x400FC1C8))

#define rIOCON_P1_02	(*(volatile unsigned *)(0x4002C088))
#define rPCONP		(*(volatile unsigned *)(0x400FC0C4))

#define rPWM0IR 	(*(volatile unsigned *)(0x40014000))
#define rPWM0TCR	(*(volatile unsigned *)(0x40014004))
#define rPWM0TC		(*(volatile unsigned *)(0x40014008))
#define rPWM0PR 	(*(volatile unsigned *)(0x4001400C))
#define rPWM0CTCR	(*(volatile unsigned *)(0x40014070))
#define rPWM0MCR	(*(volatile unsigned *)(0x40014014))
#define rPWM0MR0	(*(volatile unsigned *)(0x40014018))
#define rPWM0MR1	(*(volatile unsigned *)(0x4001401C))
#define rPWM0CCR	(*(volatile unsigned *)(0x40014028))
#define rPWM0PCR	(*(volatile unsigned *)(0x4001404C))
#define rPWM0LER	(*(volatile unsigned *)(0x40014050))

#define rISER1  	(*(volatile unsigned *)(0xE000E104))
#define rCER1		(*(volatile unsigned *)(0xE000E184))

unsigned int duty = 10;
unsigned char match_cnt = 0;

void PWM0_IRQHandler(void)
{
	if(rPWM0IR&0x1)
	{
		rFIO1PIN |= (1<<18);
		match_cnt++;
		rPWM0IR |= 0x1; 	//MR0中断复位
	}
	
	if(rPWM0IR&(0x1<<1))
	{
		rFIO1PIN &= ~(1<<18);
		rPWM0IR |= 0x1<<1;  //MR1中断复位
	}
}

void SystemInit()  
{  
    rSCS &= ~(0x1<<4);                //频率12M  
    rSCS |= (0x1<<5);             //使能主振荡器  
    while(0 == (rSCS & (0x1<<6)));//等待主振荡器稳定  
      
    rCLKSRCSEL = 0x1;  
      
    rPLL0CFG = 0x9;                 //配置CCLK = 120M  
    rPLL0CON = 0x01;  
    rPLL0FEED = 0xAA;  
    rPLL0FEED =0x55;  
    while( 0 == (rPLL0STAT & (0x1<<10)));   
      
    rCCLKSEL = (0x1 | (0x1<<8));  
    rPCLKSEL = 0x2;                 //配置PCLK = 60M  
      
    rCLKOUTCFG = 0x0 | (0xb<<4) | (0x1<<8);  
} 


void PWMInit()
{
	rIOCON_P1_02 &= ~0x7;
	rIOCON_P1_02 |= 0x3;	//P1.02配置成PWM0[1]
	
	rPCONP |= 0x1<<5; 	//使能PWM0外设
	
	rPWM0IR = 0x73F;	//初始化PWM相关控制寄存器
	rPWM0TCR = 0;
	rPWM0CTCR = 0;
	rPWM0MCR = 0;
	rPWM0CCR = 0;
	rPWM0PCR = 0;
	rPWM0LER = 0;
	
	rPWM0PR = 0x1<<20;	//每0x1<<20+1个PLCK上升沿，TC递增
	rPWM0TCR |= 0x1<<1; 	//复位TC和PC
	rPWM0TCR &= ~(0x1<<1);
	
	rPWM0MR0 = 100;
	rPWM0LER |= 0x1;
	rPWM0MCR |= 0x1<<1 | 0x1; 	//MR0和TC匹配时复位TC和PC.并且产生中断
	
	rPWM0MR1 = duty;
	rPWM0LER |= 0x1<<1;
	rPWM0MCR |= 0x1<<3; 	//MR1和TC匹配时产生中断
}

int main ()
{
	PWMInit();
	
	rFIO1DIR |= (0x1<<18);
	rISER1 |= 0x1<<7;	//PWM0中断使能
	
	rPWM0TCR |= 0x1<<1; 	//复位TC和PC
	rPWM0TCR &= ~(0x1<<1);
	
	rPWM0TCR |= 0x1;	//PC和TC计数使能
	rPWM0TCR |= 0x1<<3; //PWM模式使能
	
	while(1)
	{
		if(match_cnt >= 1)
		{
			match_cnt = 0;
			duty = duty+10;
			if(duty >= 100)
			{
				duty  = 0;
			}
			rPWM0MR1 = duty;
			rPWM0LER |= 0x1<<1;
			rPWM0MCR |= 0x1<<3;
		}
	}
	return 1;
}

        程序在MR0匹配时复位TC，在MR1匹配时触发边沿。可以看到随着MR1匹配值的改变，LED灯的亮灭时间对应改变。（程序中的预分频寄存器PR设置为了让LED效果明显）

 

        LPC1788的PWM可以进行双边沿的控制。如PWM0.2可以用MR0控制PWM的周期频率，用MR1和MR2控制PWM0.2的边沿。

posted on 2012-09-26 19:12  tdyizhen1314  阅读(2035)  评论(0)  编辑  收藏  举报

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