请教香主,stm32里面的CAN设置问题

只看该作者 · 2010-6-3 15:17

文档里面有这样一段话：

不需要在初始化模式下进行过滤器初值的设置，但必须在它处在非激活状态下完成(相应的FACT位为0)。而过滤器的位宽和模式的设置，则必须在初始化模式中进入正常模式前完成。

而我使用的官方例子，初始化程序部分如下：

/* CAN cell init */  // 36M 100k速率
  CAN_InitStructure.CAN_TTCM=DISABLE;
  CAN_InitStructure.CAN_ABOM=DISABLE;
  CAN_InitStructure.CAN_AWUM=DISABLE;
  CAN_InitStructure.CAN_NART=DISABLE;
  CAN_InitStructure.CAN_RFLM=DISABLE;
  CAN_InitStructure.CAN_TXFP=DISABLE;
  CAN_InitStructure.CAN_Mode=CAN_Mode_LoopBack;
  CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;
  CAN_InitStructure.CAN_BS1=CAN_BS1_12tq;
  CAN_InitStructure.CAN_BS2=CAN_BS2_3tq;
  CAN_InitStructure.CAN_Prescaler=22;
  CAN_Init(CAN1, &CAN_InitStructure);
/* CAN filter init */
  CAN_FilterInitStructure.CAN_FilterNumber=0;
  CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;
  CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;
  CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000;
  CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;
  CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0x0000;
  CAN_FilterInitStructure.CAN_FilterMaskIdLow=0x0000;
  CAN_FilterInitStructure.CAN_FilterFIFOAssignment=0;
  CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;
  CAN_FilterInit(&CAN_FilterInitStructure);

据我对这段程序的理解，这个过滤器的位宽和模式的设置，应该是在正常模式完成的，与文档的叙述貌似不一致。

不过在环回模式下程序跑的很正常，香主指点下，看我哪里理解错了。

只看该作者 · 2010-6-3 15:24

还有，图207里面关于仲裁域的位数，应该是写错了吧，或者stm32里面的表达不一样？

只看该作者 · 2010-6-3 15:37

CAN_FilterInit(&CAN_FilterInitStructure);
这个函数里面，是不是有进入初始化模式的代码？

只看该作者 · 2010-6-3 15:43

CAN_FilterInit的原型如下
/**
  * @brief  Initializes the CAN peripheral according to the specified
  * parameters in the CAN_FilterInitStruct.
  * @param CAN_FilterInitStruct: pointer to a CAN_FilterInitTypeDef
  * structure that contains the configuration information.
  * @retval : None.
  */
void CAN_FilterInit(CAN_FilterInitTypeDef* CAN_FilterInitStruct)
{
  uint32_t filter_number_bit_pos = 0;
  /* Check the parameters */
  assert_param(IS_CAN_FILTER_NUMBER(CAN_FilterInitStruct->CAN_FilterNumber));
  assert_param(IS_CAN_FILTER_MODE(CAN_FilterInitStruct->CAN_FilterMode));
  assert_param(IS_CAN_FILTER_SCALE(CAN_FilterInitStruct->CAN_FilterScale));
  assert_param(IS_CAN_FILTER_FIFO(CAN_FilterInitStruct->CAN_FilterFIFOAssignment));
  assert_param(IS_FUNCTIONAL_STATE(CAN_FilterInitStruct->CAN_FilterActivation));
  filter_number_bit_pos =
  (uint32_t)(((uint32_t)0x00000001) << ((uint32_t)CAN_FilterInitStruct->CAN_FilterNumber));
  /* Initialisation mode for the filter */
  CAN1->FMR |= FMR_FINIT;
  /* Filter Deactivation */
  CAN1->FA1R &= ~(uint32_t)filter_number_bit_pos;
  /* Filter Scale */
  if (CAN_FilterInitStruct->CAN_FilterScale == CAN_FilterScale_16bit)
  {
/* 16-bit scale for the filter */
CAN1->FS1R &= ~(uint32_t)filter_number_bit_pos;
/* First 16-bit identifier and First 16-bit mask */
/* Or First 16-bit identifier and Second 16-bit identifier */
CAN1->sFilterRegister[CAN_FilterInitStruct->CAN_FilterNumber].FR1 =
((uint32_t)((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterMaskIdLow) << 16) |
      ((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterIdLow);
/* Second 16-bit identifier and Second 16-bit mask */
/* Or Third 16-bit identifier and Fourth 16-bit identifier */
CAN1->sFilterRegister[CAN_FilterInitStruct->CAN_FilterNumber].FR2 =
((uint32_t)((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterMaskIdHigh) << 16) |
      ((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterIdHigh);
  }
  if (CAN_FilterInitStruct->CAN_FilterScale == CAN_FilterScale_32bit)
  {
/* 32-bit scale for the filter */
CAN1->FS1R |= filter_number_bit_pos;
/* 32-bit identifier or First 32-bit identifier */
CAN1->sFilterRegister[CAN_FilterInitStruct->CAN_FilterNumber].FR1 =
((uint32_t)((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterIdHigh) << 16) |
      ((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterIdLow);
/* 32-bit mask or Second 32-bit identifier */
CAN1->sFilterRegister[CAN_FilterInitStruct->CAN_FilterNumber].FR2 =
((uint32_t)((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterMaskIdHigh) << 16) |
      ((uint32_t)0x0000FFFF & CAN_FilterInitStruct->CAN_FilterMaskIdLow);
  }
  /* Filter Mode */
  if (CAN_FilterInitStruct->CAN_FilterMode == CAN_FilterMode_IdMask)
  {
/*Id/Mask mode for the filter*/
CAN1->FM1R &= ~(uint32_t)filter_number_bit_pos;
  }
  else /* CAN_FilterInitStruct->CAN_FilterMode == CAN_FilterMode_IdList */
  {
/*Identifier list mode for the filter*/
CAN1->FM1R |= (uint32_t)filter_number_bit_pos;
  }
  /* Filter FIFO assignment */
  if (CAN_FilterInitStruct->CAN_FilterFIFOAssignment == CAN_FilterFIFO0)
  {
/* FIFO 0 assignation for the filter */
CAN1->FFA1R &= ~(uint32_t)filter_number_bit_pos;
  }
  if (CAN_FilterInitStruct->CAN_FilterFIFOAssignment == CAN_FilterFIFO1)
  {
/* FIFO 1 assignation for the filter */
CAN1->FFA1R |= (uint32_t)filter_number_bit_pos;
  }

  /* Filter activation */
  if (CAN_FilterInitStruct->CAN_FilterActivation == ENABLE)
  {
CAN1->FA1R |= filter_number_bit_pos;
  }
  /* Leave the initialisation mode for the filter */
  CAN1->FMR &= ~FMR_FINIT;
}

这个函数里面貌似没有进入初始化模式的代码。

只看该作者 · 2010-6-3 16:29

过滤器的设置一般是在初始化里设置的

只看该作者 · 2010-6-3 16:47

问题是官方下载的测试程序貌似并没有这样做，所以搞的我很疑惑，还希望各位帮忙解惑。

1万 · 2010-6-4 09:47

本帖最后由 IJK 于 2010-6-4 09:50 编辑

看了一下中文翻译，它有点自相矛盾：
1）在对bxCAN的过滤器组(模式、位宽、FIFO关联、激活和过滤器值)进行初始化前，软件要对CAN_FMR寄存器的FINIT位设置’1’。对过滤器的初始化可以在非初始化模式下进行。

2）不需要在初始化模式下进行过滤器初值的设置，但必须在它处在非激活状态下完成(相应的FACT位为0)。而过滤器的位宽和模式的设置，则必须在初始化模式中进入正常模式前完成。

再看了一下英文原文，第2）段有点问题，不是“则必须在初始化模式中进入正常模式前完成”，应该改为“则必须在进入正常模式前完成”。
第1）段，改为“对过滤器的初始化可以在非初始化模式（睡眠模式）下进行。”

对应于源代码，一般是：
/* CAN filter init */
  CAN_FilterInitStructure.CAN_FilterNumber=0;
  CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;
  CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;
  CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000;
  CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;
  CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0x0000;
  CAN_FilterInitStructure.CAN_FilterMaskIdLow=0x0000;
  CAN_FilterInitStructure.CAN_FilterFIFOAssignment=0;
  CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;
  CAN_FilterInit(&CAN_FilterInitStructure);
//......
  //Enter Normal mode from sleep mode
  CAN_WakeUp();
即在睡眠模式下初始化CAN过滤器。

只看该作者 · 2010-6-4 14:49

谢谢LS的细心解答。
我用的是3.0.0版本，貌似CAN_WakeUp(); 这个函数都没有用到，不过目前初步测试一切正常，并无不妥之处。

只看该作者 · 2010-6-4 17:30

看清楚寄存器的设置就行

只看该作者 · 2010-6-5 09:20

一切正常就说明你的初始化没问题

请教香主,stm32里面的CAN设置问题

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