Cortex-M3 (NXP LPC1788)之PWM

1. R&(0x1<1))
2. {
3. rFIO1PIN&=~(1<18);
4. rPWM0IR|=0x1<1;//MR1中断复位
5. }
6. }
8. voidSystemInit()
9. {
10. rSCS&=~(0x1<4);//频率12M
11. rSCS|=(0x1<5);//使能主振荡器
12. while(0==(rSCS&(0x1<6)));//等待主振荡器稳定
14. rCLKSRCSEL=0x1;
16. rPLL0CFG=0x9;//配置CCLK=120M
17. rPLL0CON=0x01;
18. rPLL0FEED=0xAA;
19. rPLL0FEED=0x55;
20. while(0==(rPLL0STAT&(0x1<10)));
22. rCCLKSEL=(0x1|(0x1<8));
23. rPCLKSEL=0x2;//配置PCLK=60M
25. rCLKOUTCFG=0x0|(0xb<4)|(0x1<8);
26. }
29. voidPWMInit()
30. {
31. rIOCON_P1_02&=~0x7;
32. rIOCON_P1_02|=0x3;//P1.02配置成PWM0[1]
34. rPCONP|=0x1<5;//使能PWM0外设
36. rPWM0IR=0x73F;//初始化PWM相关控制寄存器
37. rPWM0TCR=0;
38. rPWM0CTCR=0;
39. rPWM0MCR=0;
40. rPWM0CCR=0;
41. rPWM0PCR=0;
42. rPWM0LER=0;
44. rPWM0PR=0x1<20;//每0x1<20+1个PLCK上升沿，TC递增
45. rPWM0TCR|=0x1<1;//复位TC和PC
46. rPWM0TCR&=~(0x1<1);
48. rPWM0MR0=100;
49. rPWM0LER|=0x1;
50. rPWM0MCR|=0x1<1|0x1;//MR0和TC匹配时复位TC和PC.并且产生中断
52. rPWM0MR1=duty;
53. rPWM0LER|=0x1<1;
54. rPWM0MCR|=0x1<3;//MR1和TC匹配时产生中断
55. }
57. intmain()
58. {
59. PWMInit();
61. rFIO1DIR|=(0x1<18);
62. rISER1|=0x1<7;//PWM0中断使能
64. rPWM0TCR|=0x1<1;//复位TC和PC
65. rPWM0TCR&=~(0x1<1);
67. rPWM0TCR|=0x1;//PC和TC计数使能
68. rPWM0TCR|=0x1<3;//PWM模式使能
70. while(1)
71. {
72. if(match_cnt>=1)
73. {
74. match_cnt=0;
75. duty=duty+10;
76. if(duty>=100)
77. {
78. duty=0;
79. }
80. rPWM0MR1=duty;
81. rPWM0LER|=0x1<1;
82. rPWM0MCR|=0x1<3;
83. }
84. }
85. return1;
86. }

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。