让 bxCan 在 STM32f3 Discovery 上工作

Question

我正在努力让 bxcan on stm32f3 discovery 正常工作。我创建了一个简单的程序，它通过 bxcan 发送消息，并在实验室中使用 osci 和在家中使用万用表检查引脚 PA11 和 PA12。到目前为止，osci 和万用表显示没有信号传输——tx 和 rx 引脚都堆叠在 0V。这是代码：

#define CANx                       CAN1
#define CAN_CLK                    RCC_APB1Periph_CAN1
#define CAN_RX_PIN                 GPIO_Pin_11
#define CAN_TX_PIN                 GPIO_Pin_12
#define CAN_GPIO_PORT              GPIOA
#define CAN_GPIO_CLK               RCC_AHBPeriph_GPIOA
#define CAN_AF_PORT                GPIO_AF_9
#define CAN_RX_SOURCE              GPIO_PinSource11
#define CAN_TX_SOURCE              GPIO_PinSource12   
int main(void)
{
   CAN_Config();
while(1)
  {
      TxMessage.Data[0] = KeyNumber;
      CAN_Transmit(CANx, &TxMessage);
      Delay();
  }
}

/**
  * @brief  Configures the CAN.
  * @param  None
  * @retval None
  */
static void CAN_Config(void)
{
  GPIO_InitTypeDef  GPIO_InitStructure;
  NVIC_InitTypeDef  NVIC_InitStructure;
  CAN_InitTypeDef        CAN_InitStructure;
  CAN_FilterInitTypeDef  CAN_FilterInitStructure;

  /* CAN GPIOs configuration **************************************************/

  /* Enable GPIO clock */
  RCC_AHBPeriphClockCmd(CAN_GPIO_CLK, ENABLE);

  /* Connect CAN pins to AF9 */
  GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_RX_SOURCE, CAN_AF_PORT);
  GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_TX_SOURCE, CAN_AF_PORT); 

  /* Configure CAN RX and TX pins */
  GPIO_InitStructure.GPIO_Pin = CAN_RX_PIN | CAN_TX_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
  GPIO_Init(CAN_GPIO_PORT, &GPIO_InitStructure);

  /* NVIC configuration *******************************************************/
  NVIC_InitStructure.NVIC_IRQChannel = USB_LP_CAN1_RX0_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  //TODO:Enable NVIC_Init(&NVIC_InitStructure);

  /* CAN configuration ********************************************************/  
  /* Enable CAN clock */
  RCC_APB1PeriphClockCmd(CAN_CLK, ENABLE);

  /* CAN register init */
  CAN_DeInit(CANx);
  CAN_StructInit(&CAN_InitStructure);

  /* CAN cell init */
  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_Normal;
  CAN_InitStructure.CAN_SJW = CAN_SJW_1tq;

  /* CAN Baudrate = 1MBps (CAN clocked at 36 MHz) */
  CAN_InitStructure.CAN_BS1 = CAN_BS1_9tq;
  CAN_InitStructure.CAN_BS2 = CAN_BS2_8tq;
  CAN_InitStructure.CAN_Prescaler = 2;
  CAN_Init(CANx, &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);

  /* Transmit Structure preparation */
  TxMessage.StdId = 0x321;
  TxMessage.ExtId = 0x01;
  TxMessage.RTR = CAN_RTR_DATA;
  TxMessage.IDE = CAN_ID_STD;
  TxMessage.DLC = 1;

  /* Enable FIFO 0 message pending Interrupt */
  CAN_ITConfig(CANx, CAN_IT_FMP0, ENABLE);
}

到目前为止，我可以声明代码编译时出现 0 个警告和错误，并且调试器显示相应总线的激活时钟。我检查了 std 用户手册，根据它 bxcan 配置是正确的。不知何故它不起作用...（我对 CAN 的经验为 0）。

Answer 1

在花了一些时间在这里和那里寻找解决方案后，我终于发现在 stm32f3 的数据表中发现应该连接（焊接）开关 sb21 和 sb22 以将它们连接到 CAN。这样做就成功了。

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