title: How to configure the STM32103 for CAN and remapping the pins to PB8 and PB9
body: <p>I am trying to, at this stage, simply send a transmission using CAN on the STM32F103 V8T6.  The chip is implemented on a board that was customized by my company.  Looking at the schematic I see that the CAN Tx and Rx pins were remapped to PB9 (Tx) and PB8 (Rx).  All that being said, I have been able to use LoopBack mode successfully (using the latest example from STM "V3.5.0") but have have NOT been able to get Normal mode working.  Can someone please let me know if they see an obvious flaw in my initial configuration?!  I have included only the code related to configuration and left out the transmission function call.</p>
  
  <pre><code>int main (void)
  {
  
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
  
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
  
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_CAN1, ENABLE);
  
  
  
  NVIC_InitTypeDef NVIC_InitStructure;
  
  NVIC_InitStructure.NVIC_IRQChannel = USB_LP_CAN1_RX0_IRQn;
  
  NVIC_InitStructure.NVIC_IRQChannel = CAN1_RX0_IRQn;
  
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  
  NVIC_Init(&amp;NVIC_InitStructure);
  
  
  
   GPIO_InitTypeDef GPIO_InitStructure;
  
  
  /* Configure CAN pin: RX */
  
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
  
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
  
  GPIO_Init(GPIOB, &amp;GPIO_InitStructure);
  
  
  /* Configure CAN pin: TX */
  
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
  
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  
  GPIO_Init(GPIOB, &amp;GPIO_InitStructure);
  
  
  // Remap2 is for PB8 and PB9
  
  GPIO_PinRemapConfig(GPIO_Remap2_CAN1 , ENABLE);
  
  
  }
  </code></pre>
  
  <p>Here is my transmit function</p>
  
  <pre><code>void CAN_TransmitMyMsg(void)
  {
    CAN_InitTypeDef        CAN_InitStructure;
    CAN_FilterInitTypeDef  CAN_FilterInitStructure;
    CanTxMsg TxMessage;
    uint32_t i = 0;
    uint8_t TransmitMailbox = 0;
    uint8_t status = 0;
  
    /* CAN register init */
    CAN_DeInit(CANx);
    CAN_StructInit(&amp;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;
  
    /* Baudrate = 125kbps*/
    CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;
    CAN_InitStructure.CAN_BS1=CAN_BS1_2tq;
    CAN_InitStructure.CAN_BS2=CAN_BS2_3tq;
    CAN_InitStructure.CAN_Prescaler=48;
    CAN_Init(CANx, &amp;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(&amp;CAN_FilterInitStructure);
  
    /* transmit */
    TxMessage.StdId=0x11;
    TxMessage.RTR=CAN_RTR_DATA;
    TxMessage.IDE=CAN_ID_STD;
    TxMessage.DLC=2;
    TxMessage.Data[0]=0xCA;
    TxMessage.Data[1]=0xFE;
  
    TransmitMailbox=CAN_Transmit(CANx, &amp;TxMessage);
  
    //wait until CAN transmission is OK
    i = 0;
    while((status != CANTXOK) &amp;&amp; (i != 0xFFFF))               
    {
      status = CAN_TransmitStatus(CANx, TransmitMailbox);
      i++;
    }
  
  }
  </code></pre>
  
  <p>This resource has been helpful, but ultimately insufficient. </p>
  
  <p><a href="https://stackoverflow.com/questions/6195033/stm32f103-micro-controller-can-messages">STM32F103 microcontroller CAN messages</a></p>
  
  <p>Thanks!</p>
  
  <p>Daniel</p>