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Problem with CAN config and Clock STM32F407VG

Question asked by leaure on Jul 17, 2013
Latest reply on Jul 18, 2013 by leaure
Hi,

I have a problem with my CAN configuration, I try to interface the STM32 with a NI USB/CAN.
The problem is the baudrate configuration I think, see my code below :

GPIO_InitTypeDef  GPIO_InitStructure;
 
  /* CAN GPIOs configuration **************************************************/
 
  /* Enable GPIO clock */
  RCC_AHB1PeriphClockCmd(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);
 
  /* 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 30 MHz) */
  CAN_InitStructure.CAN_BS1 = CAN_BS1_14tq;
  CAN_InitStructure.CAN_BS2 = CAN_BS2_6tq;
  CAN_InitStructure.CAN_Prescaler = 5;
  CAN_Init(CANx, &CAN_InitStructure);
 
  /* CAN filter init */
#ifdef  USE_CAN1
  CAN_FilterInitStructure.CAN_FilterNumber = 0;
#else /* USE_CAN2 */
  CAN_FilterInitStructure.CAN_FilterNumber = 14;
#endif  /* USE_CAN1 */
  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.StdId = 0x0;
  TxMessage.ExtId = 0x01;
  TxMessage.RTR = CAN_RTR_DATA;
  TxMessage.IDE = CAN_ID_STD;
  TxMessage.DLC = 8;
   
  /* Enable FIFO 0 message pending Interrupt */
  CAN_ITConfig(CANx, CAN_IT_FMP0, ENABLE);

I config with :
CAN_InitStructure.CAN_BS1 = CAN_BS1_14tq;

CAN_InitStructure.CAN_BS2 = CAN_BS2_6tq;

CAN_InitStructure.CAN_Prescaler = 5;

In order to have a baudrate @ 400kb/s, this calculation is base on a frequency of 42MHz for the PCLK1.
If I check the HCKL, the value is 134222613Hz (check with RCC_GetClockFreq)  not 168MHz, I don't understand why?
Same think for SYSCLK, the value is 5370011984Hz???
I perform a SystemInit to reset the clocks but nothing works.

Does someone have an idea ?

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