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       最近用STM32调制PWM信号输出，我用TIM1产生7路PWM输出，但是在设置PWM信号占空比时出现这样一个问题，当后面通道输出的占空比，比前面通道输出占空比大时，前面通道的信号占空比，都会和后面这个信号占空比一样大（例如 : CCR2 > CCR1，信号输出占空比PWM1 = PWM2，当CCR2<CCR1，信号输出占空比正常）

程序就是用的官方程序，只是修改过频率和占空比参数。

/**
  ******************************************************************************
  * @file    TIM/7PWM_Output/main.c 
  * @author  MCD Application Team
  * @version V3.5.0
  * @date    08-April-2011
  * @brief   Main program body
  ******************************************************************************
  * @attention
  *
  * THE PRESENT FIRMWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS
  * WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE
  * TIME. AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY
  * DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING
  * FROM THE CONTENT OF SUCH FIRMWARE AND/OR THE USE MADE BY CUSTOMERS OF THE
  * CODING INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.
  *
  * <h2><center>&copy; COPYRIGHT 2011 STMicroelectronics</center></h2>
  ******************************************************************************
  */ 

/* Includes ------------------------------------------------------------------*/
#include "stm32f10x.h"

/** @addtogroup STM32F10x_StdPeriph_Examples
  * @{
  */

/** @addtogroup TIM_7PWM_Output
  * @{
  */ 

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
uint16_t TimerPeriod = 0;
uint16_t Channel1Pulse = 0, Channel2Pulse = 0, Channel3Pulse = 0, Channel4Pulse = 0;

/* Private function prototypes -----------------------------------------------*/
void RCC_Configuration(void);
void GPIO_Configuration(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief   Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured, 
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f10x_xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f10x.c file
     */     
       
  /* System Clocks Configuration */
  RCC_Configuration();

  /* GPIO Configuration */
  GPIO_Configuration();

  /* TIM1 Configuration ---------------------------------------------------
   Generate 7 PWM signals with 4 different duty cycles:
   TIM1CLK = SystemCoreClock, Prescaler = 0, TIM1 counter clock = SystemCoreClock
   SystemCoreClock is set to 72 MHz for Low-density, Medium-density, High-density
   and Connectivity line devices and to 24 MHz for Low-Density Value line and
   Medium-Density Value line devices
   
   The objective is to generate 7 PWM signal at 50Hz:
     - TIM1_Period = 2000 - 1
   The channel 1 and channel 1N duty cycle is set to 10%
   The channel 2 and channel 2N duty cycle is set to 37.5%
   The channel 3 and channel 3N duty cycle is set to 25%
   The channel 4 duty cycle is set to 12.5%
   The Timer pulse is calculated as follows:
     - ChannelxPulse = DutyCycle * (TIM1_Period - 1) / 100
  ----------------------------------------------------------------------- */
  /* Compute the value to be set in ARR regiter to generate signal frequency at 50hz */
  TimerPeriod = 2000 - 1;
  /* Compute CCR1 value to generate a duty cycle at 10% for channel 1 and 1N */
  Channel1Pulse = (uint16_t) (((uint32_t) 10 * (TimerPeriod - 1)) / 100);
  /* Compute CCR2 value to generate a duty cycle at 37.5%  for channel 2 and 2N */
  Channel2Pulse = (uint16_t) (((uint32_t) 375 * (TimerPeriod - 1)) / 1000);
  /* Compute CCR3 value to generate a duty cycle at 25%  for channel 3 and 3N */
  Channel3Pulse = (uint16_t) (((uint32_t) 25 * (TimerPeriod - 1)) / 100);
  /* Compute CCR4 value to generate a duty cycle at 12.5%  for channel 4 */
  Channel4Pulse = (uint16_t) (((uint32_t) 125 * (TimerPeriod- 1)) / 1000);

  /* Time Base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 720;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

  /* Channel 1, 2,3 and 4 Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM_OCInitStructure.TIM_Pulse = Channel1Pulse;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

  TIM_OC1Init(TIM1, &TIM_OCInitStructure);

  TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
  TIM_OC2Init(TIM1, &TIM_OCInitStructure);

  TIM_OCInitStructure.TIM_Pulse = Channel3Pulse;
  TIM_OC3Init(TIM1, &TIM_OCInitStructure);

  TIM_OCInitStructure.TIM_Pulse = Channel4Pulse;
  TIM_OC4Init(TIM1, &TIM_OCInitStructure);

  /* TIM1 counter enable */
  TIM_Cmd(TIM1, ENABLE);

  /* TIM1 Main Output Enable */
  TIM_CtrlPWMOutputs(TIM1, ENABLE);

  while (1)
  {}
}

/**
  * @brief  Configures the different system clocks.
  * @param  None
  * @retval None
  */
void RCC_Configuration(void)
{
  /* TIM1, GPIOA, GPIOB, GPIOE and AFIO clocks enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1 | RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOE|
                         RCC_APB2Periph_GPIOB |RCC_APB2Periph_AFIO, ENABLE);
}

/**
  * @brief  Configure the TIM1 Pins.
  * @param  None
  * @retval None
  */
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

#ifdef STM32F10X_CL
  /* GPIOE Configuration: Channel 1/1N, 2/2N, 3/3N and 4 as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_11|GPIO_Pin_13|GPIO_Pin_14|
                                GPIO_Pin_8|GPIO_Pin_10|GPIO_Pin_12;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_Init(GPIOE, &GPIO_InitStructure);

  /* TIM1 Full remapping pins */
  GPIO_PinRemapConfig(GPIO_FullRemap_TIM1, ENABLE); 

#else
  /* GPIOA Configuration: Channel 1, 2 and 3 as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* GPIOB Configuration: Channel 1N, 2N and 3N as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

#endif
}

#ifdef  USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  while (1)
  {}
}

#endif

/**
  * @}
  */ 

/**
  * @}
  */ 

/******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE****/

    求大神给个合理解释~~还有解决方法~ 谢谢了~~