STM32学习笔记-PWM波形输出.doc

调试芯片：STM32F103C8T6外部晶振：8MHz功能介绍：使用Timer3实现两路（可四路）PWM波形的输出代码如下： 初始化：系统时钟初始化，GPIO端口初始化，Timer初始化系统时钟初始化：1. /*配置系统时钟为72M*/2. SystemInit();GPIO端口初始化：1. /*2. *函数名：voidGPIO_Config(void)3. *描述：配置复用输出PWM时用到的I/O4. *输入：无5. *输出：无6. *调用：main()调用7. */8. voidGPIO_Config(void)9. 10. GPIO_InitTypeDefGPIO_InitStructure;11. 12. /*GPIOAandGPIOBclockenable*/13. RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);14. 15. /*GPIOAConfiguration:TIM3channel1and2asalternatefunctionpush-pull*/16. GPIO_InitStructure.GPIO_Pin=GPIO_Pin_6|GPIO_Pin_7;17. GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;/复用推挽输出18. GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;19. GPIO_Init(GPIOA,&GPIO_InitStructure);20. Timer初始化:1. /*2. *函数名：voidTIM3_Config(void)3. *描述：配置TIM3输出的PWM信号的模式4. *CH1:输出T=2.5ms(f=1/2.5ms=400Hz)D=0.6的PWM波(高电平在前，低电平在后)5. *CH2:输出T=2.5ms(f=1/2.5ms=400Hz)D=0.4的PWM波(高电平在后，低电平在前)6. *步骤一：通过T和TIMxCLK的时钟源确定TIM_Period和TIM_Prescaler7. *T=(TIM_Period+1)*(TIM_Prescaler+1)/TIMxCLK=2.5ms8. *因为TIM_Period1,即TIM_Prescaler=29. *所以TIM_Period=59999=0xEA5F10. *步骤二：根据TIM_Period的值，高低电平的先后D，确定CCR和TIM_OCPolarity11. *CH1：因为D=0.6，先高后低；12. *所以CCR1=(TIM_Period+1)*D=36000;TIM_OCPolarity=TIM_OCPolarity_High13. *CH2：因为D=0.4，先高后低；14. *所以CCR1=(TIM_Period+1)*(1-D)=36000;TIM_OCPolarity=TIM_OCPolarity_Low15. *步骤三：基础寄存器初始化16. *步骤四：通道寄存器初始化17. *步骤五：使能TIM3重载寄存器ARR18. *步骤六：使能TIM319. *输入：无20. *输出：无21. *调用：main()调用22. */23. voidTIM3_Config(void)24. 25. TIM_TimeBaseInitTypeDefTIM_TimeBaseStructure;26. TIM_OCInitTypeDefTIM_OCInitStructure;27. /*PWM信号电平跳变值*/28. u16CCR1=36000;29. u16CCR2=36000;30. /*PCLK1经过2倍频后作为TIM3的时钟源等于72MHz*/31. RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);32. /*Timebaseconfiguration*/33. TIM_TimeBaseStructure.TIM_Period=0xEA5F;34. TIM_TimeBaseStructure.TIM_Prescaler=2;/设置预分频：预分频=2，即为72/3=24MHz35. TIM_TimeBaseStructure.TIM_ClockDivision=0;/设置时钟分频系数：不分频36. TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;/向上计数溢出模式37. TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);38. /*PWM1Modeconfiguration:Channel1*/39. TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM1;/配置为PWM模式140. TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;41. TIM_OCInitStructure.TIM_Pulse=CCR1;/设置跳变值，当计数器计数到这个值时，电平发生跳变42. TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_High;/当定时器计数值小于CCR1时为高电平43. TIM_OC1Init(TIM3,&TIM_OCInitStructure);/使能通道144. TIM_OC1PreloadConfig(TIM3,TIM_OCPreload_Enable);45. /*PWM1Modeconfiguration:Channel2*/46. TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;47. TIM_OCInitStructure.TIM_Pulse=CCR2;/设置通道2的电平跳变值，输出另外一个占空比的PWM48. TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low;/当定时器计数值小于CCR2时为低电平49. TIM_OC2Init(TIM3,&TIM_OCInitStructure);/使能通道250. TIM_OC2PreloadConfig(TIM3,TIM_OCPreload_Enable);51. TIM_ARRPreloadConfig(TIM3,ENABLE);/使能TIM3重载寄存器ARR52. /*TIM3enablecounter*/53. TIM_Cmd(TIM3,ENABLE);/使能TIM354. 主函数代码:1. /*2. *函数名：main3. *描述：主函数4. *输入：无5. *输出：无6.