STM32 PWM 模式中 DMA传输为什么要用到4个BUFFER

只看该作者 · 2010-6-28 17:13

本帖最后由 fanhoufa 于 2010-6-28 17:17 编辑

u16 hCCDmaBuffCh1[4];
u16 hCCDmaBuffCh2[4];
u16 hCCDmaBuffCh3[4];
u16 hCCDmaBuffCh4[4];

  DMA_DeInit(DMA1_Channel2);
  DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)TIM1_CCR1_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (u32)(hCCDmaBuffCh1);
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 4;
  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);
  //Enable DMA Channel2 //
  //DMA_Cmd(DMA_Channel2, ENABLE);
  DMA_Cmd(DMA1_Channel2, DISABLE);

  // TIM1 Channel 2 toggle mode /
  //DMA Channel3 configuration ----------------------------------------------//
  DMA_DeInit(DMA1_Channel3);
  DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)TIM1_CCR2_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (u32)(hCCDmaBuffCh2);
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 4;
  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_Channel3, &DMA_InitStructure);
  //Enable DMA Channel3 //
  //DMA_Cmd(DMA_Channel3, ENABLE);
  DMA_Cmd(DMA1_Channel3, DISABLE);

  // TIM1 Channel 3 toggle mode //
  // DMA Channel6 configuration ----------------------------------------------//
  DMA_DeInit(DMA1_Channel6);
  DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)TIM1_CCR3_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (u32)(hCCDmaBuffCh3);
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 4;
  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_Channel6, &DMA_InitStructure);
  // Enable DMA Channel6 //
  DMA_Cmd(DMA1_Channel6, DISABLE);

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
//启动TIM1
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);

   /* TIM1 Peripheral Configuration -------------------------------------------*/
  // TIM1 Registers reset //
  TIM_DeInit(TIM1);
  TIM_TimeBaseStructInit(&TIM1_TimeBaseStructure);
  // Time Base configuration /
  TIM1_TimeBaseStructure.TIM_Prescaler = 0x0;

  TIM1_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_CenterAligned3;
  TIM1_TimeBaseStructure.TIM_Period = PWM_PERIOD;
  TIM1_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

  // Initial condition is REP=0 to set the UPDATE only on the underflow
  TIM1_TimeBaseStructure.TIM_RepetitionCounter = REP_RATE;
  TIM_TimeBaseInit(TIM1, &TIM1_TimeBaseStructure);

  TIM_OCStructInit(&TIM1_OCInitStructure);
  // Channel 1, 2,3 in PWM mode /
  TIM1_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM1_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM1_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM1_OCInitStructure.TIM_Pulse = PWM_PERIOD >> 1; //dummy value
  TIM1_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM1_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;
  TIM1_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
  TIM1_OCInitStructure.TIM_OCNIdleState = LOW_SIDE_POLARITY;

  TIM_OC1Init(TIM1, &TIM1_OCInitStructure);
  TIM_OC3Init(TIM1, &TIM1_OCInitStructure);
  TIM_OC2Init(TIM1, &TIM1_OCInitStructure);

这个主要是电机控制过程中的PWM初始化过程。DMA主要是传输值到TIM1 -> CCR1
TIM1->CCR2 TIM2 ->CCR3 更新。
这个初始化的过程中，为什么DMA_BufferSize要用到4，而不是1.

只看该作者 · 2010-12-20 09:47

因为你的变量类型都是一个字（32位），所以DMA_BufferSize是4, 32位＝ 4字节

只看该作者 · 2010-12-20 11:04

因为你的变量类型都是一个字（32位），所以DMA_BufferSize是4, 32位＝ 4字节
jgphu 发表于 2010-12-20 09:47

DMA 缓冲区的宽度是1字节？从哪看出来的呀？

DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)TIM1_CCR1_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)(hCCDmaBuffCh1);
这两行定义外设与内存区的地址，类型转换为32 位；

DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
这两行不是定义了外设与内存区的数据大小都是 16位吗？

32 位的地址存放16位的数据，那么DMA缓冲区的宽度应该和32 位地址保持一致，也是32位宽度； DMA大小定义为4，是不是因为内存区大小也定义为获得4个数据啊？（u16 hCCDmaBuffCh1[4];）

我的理解是这样的：

DMA 缓冲区宽度不是应该保持一致吗？

STM32 PWM 模式中 DMA传输为什么要用到4个BUFFER

精华达人奖章

湍急之河流

以坛为家

技术奇才奖章