學(xué)習(xí)筆記PWM波形輸出

1、調(diào)試芯片：STM32F103C8T6外部晶振：8MHz功能介紹：使用Timer3實(shí)現(xiàn)兩路（可四路）PWM波形的輸出代碼如下：    初始化：系統(tǒng)時(shí)鐘初始化，GPIO端口初始化，Timer初始化系統(tǒng)時(shí)鐘初始化：1. /* 配置系統(tǒng)時(shí)鐘為72M */ 2. SystemInit(); GPIO端口初始化：1. /*2.  * 函數(shù)名：void GPIO_Config(void) 3.  * 描述  ：配置復(fù)用輸出PWM時(shí)用到的I/O 4.  

2、;* 輸入  ：無(wú) 5.  * 輸出  ：無(wú) 6.  * 調(diào)用  ：main()調(diào)用 7.  */ 8. void GPIO_Config(void)  9.  10.   GPIO_InitTypeDef GPIO_InitStructure; 11.  12.   /* GPIOA and GP

3、IOB clock enable */ 13.   RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);  14.  15.   /*GPIOA Configuration: TIM3 channel 1 and 2 as alternate function push-pull */ 16.   

4、;GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_6 | GPIO_Pin_7; 17.   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;           / 復(fù)用推挽輸出 18.   GPIO_InitStructure.GPIO_Speed =

5、60;GPIO_Speed_50MHz; 19.   GPIO_Init(GPIOA, &GPIO_InitStructure); 20.  Timer初始化:1. /* 2.  * 函數(shù)名：void TIM3_Config(void)  3.  * 描述  ：配置TIM3輸出的PWM信號(hào)的模式 4.  *      CH1:輸出 T=2.

6、5ms(f=1/2.5ms=400Hz)  D=0.6的PWM波(高電平在前，低電平在后) 5.  *      CH2:輸出 T=2.5ms(f=1/2.5ms=400Hz)  D=0.4的PWM波(高電平在后，低電平在前) 6.  *      步驟一：通過T和TIMxCLK的時(shí)鐘源確定TIM_Period和TIM_Prescaler  7.  *

7、60;         T=(TIM_Period+1)*(TIM_Prescaler+1)/TIMxCLK=2.5ms  8.  *          因?yàn)?#160;TIM_Period<65535，所以 TIM_Prescaler>1,即 TIM_Prescaler=2 9.  *   &#

8、160;      所以 TIM_Period=59999=0xEA5F 10.  *      步驟二：根據(jù)TIM_Period的值，高低電平的先后D，確定CCR和TIM_OCPolarity 11.  *          CH1：因?yàn)镈=0.6，先高后低； 12.  *   

9、;           所以CCR1=(TIM_Period+1)* D=36000;TIM_OCPolarity=TIM_OCPolarity_High 13.  *          CH2：因?yàn)镈=0.4，先高后低； 14.  *        

10、0;     所以CCR1=(TIM_Period+1)* (1-D)=36000;TIM_OCPolarity=TIM_OCPolarity_Low 15.  *      步驟三：基礎(chǔ)寄存器初始化 16.  *      步驟四：通道寄存器初始化 17.  *      步驟五：使能TIM3重載

11、寄存器ARR 18.  *      步驟六：使能TIM3  19.  * 輸入  ：無(wú)  20.  * 輸出  ：無(wú)  21.  * 調(diào)用  ：main()調(diào)用  22.  */  23. void TIM3_Config(void)  24.  

12、 25.     TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;  26.     TIM_OCInitTypeDef  TIM_OCInitStructure;  27.     /* PWM信號(hào)電平跳變值 */  28.     u16 CCR1=

13、 36000;          29.     u16 CCR2= 36000;  30.     /*PCLK1經(jīng)過2倍頻后作為TIM3的時(shí)鐘源等于72MHz*/  31.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); 

14、; 32.     /* Time base configuration */                                    

15、        33.     TIM_TimeBaseStructure.TIM_Period =0xEA5F;  34.     TIM_TimeBaseStructure.TIM_Prescaler = 2;              

16、0;                     /設(shè)置預(yù)分頻：預(yù)分頻=2，即為72/3=24MHz  35.     TIM_TimeBaseStructure.TIM_ClockDivision = 0;         

17、;                       /設(shè)置時(shí)鐘分頻系數(shù)：不分頻  36.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;      

18、60;          /向上計(jì)數(shù)溢出模式  37.     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);  38.     /* PWM1 Mode configuration: Channel1 */  39.   

19、  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;                           /配置為PWM模式1  40.     TIM_OCInitStructu

20、re.TIM_OutputState = TIM_OutputState_Enable;                41.     TIM_OCInitStructure.TIM_Pulse = CCR1;            

21、60;                          /設(shè)置跳變值，當(dāng)計(jì)數(shù)器計(jì)數(shù)到這個(gè)值時(shí)，電平發(fā)生跳變  42.     TIM_OCInitStructure.TIM_OCPolarity =TIM_OCPolarity_High;  

22、60;                 /當(dāng)定時(shí)器計(jì)數(shù)值小于CCR1時(shí)為高電平  43.     TIM_OC1Init(TIM3, &TIM_OCInitStructure);              

23、60;                     /使能通道1      44.     TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);  45.     /* 

24、;PWM1 Mode configuration: Channel2 */  46.     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  47.     TIM_OCInitStructure.TIM_Pulse = CCR2;       

25、60;                               /設(shè)置通道2的電平跳變值，輸出另外一個(gè)占空比的PWM  48.     TIM_OCInitStructure.TIM_OCPolarity =

26、0;TIM_OCPolarity_Low;                    /當(dāng)定時(shí)器計(jì)數(shù)值小于CCR2時(shí)為低電平 49.     TIM_OC2Init(TIM3, &TIM_OCInitStructure);         

27、60;                          /使能通道2  50.     TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  51.     T

28、IM_ARRPreloadConfig(TIM3, ENABLE);                                         /使能TIM3重載寄存器ARR  52.     /* TIM3 enable counter */  53.     TIM_Cmd(TIM3, ENABLE);