TIM+DMA 百思不得其解：只简单地修改了例程，功能就废了

只看该作者 · 2013-4-23 18:31

本帖最后由 Tenant_2013 于 2013-4-23 18:33 编辑

型号：ST32F103RBT6

例程：TIM/DMA/main.c

欲实现功能：
   使TIM1正极性端按75%、50%、25%、75%……的占空比循环不断地输出PWM。

修改：
   1. 将TIM1的相关设置放入void TIM_Configuration(void)中。这一步是简单的复制、粘贴，完成后单独测试过，没有问题。
   2. 将TIM1的正极性输出端口改为TIM1_Channel1，GPIO对应于PA.08，DMA对应于DMA1_Channel2；去掉负极性输出的相关设置。这一步就有问题了……

问题：
   TIM1始终按照初始化之后的75%占空比输出PWM波，不再随25%、50%、75%变化。

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

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define TIM1_CCR1_Address 0x40012C34

/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
uint16_t SRC_Buffer[3] = {0, 0, 0};
uint16_t TimerPeriod = 0;

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

/* Private functions ---------------------------------------------------------*/
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();

  /* DMA Configuration */
  DMA_Configuration();

  /* TIM Configuration */
  TIM_Configuration();

  while (1)
  {}
}

void RCC_Configuration(void)
{
  /* TIM1, GPIOA clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1 | RCC_APB2Periph_GPIOA, ENABLE);
  /* DMA clock enable */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
}

void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* GPIOA Configuration */
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_8;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
}

void DMA_Configuration(void)
{
  DMA_InitTypeDef DMA_InitStructure;

  /* DMA1 Channel2 Config */
  DMA_DeInit(DMA1_Channel2);

  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)TIM1_CCR1_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)SRC_Buffer;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 3;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

  DMA_Init(DMA1_Channel2, &DMA_InitStructure);

  /* DMA1 Channel2 enable */
  DMA_Cmd(DMA1_Channel2, ENABLE);
}

void TIM_Configuration(void)
{
  /* Compute the value to be set in ARR register to generate signal frequency at 17.57 Khz */
  TimerPeriod = (SystemCoreClock / 17570 ) - 1;
  /* Compute CCR1 value to generate a duty cycle at 75% */
  SRC_Buffer[0] = (uint16_t) (((uint32_t) 75 * (TimerPeriod - 1)) / 100);
  /* Compute CCR1 value to generate a duty cycle at 50% */
  SRC_Buffer[1] = (uint16_t) (((uint32_t) 5 * (TimerPeriod - 1)) / 10);
  /* Compute CCR1 value to generate a duty cycle at 25% */
  SRC_Buffer[2] = (uint16_t) (((uint32_t) 25 * (TimerPeriod - 1)) / 100);

  /* TIM1 Peripheral Configuration --------------------------------------------*/
  /* Time Base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 2;

  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

  /* Channel 1 Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = SRC_Buffer[0];
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;

  TIM_OC1Init(TIM1, &TIM_OCInitStructure);

  /* TIM1 Update DMA Request enable */
  TIM_DMACmd(TIM1, TIM_DMA_Update, ENABLE);

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

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

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

究竟问题出在哪里？望各位老手指点！