microb microb - 6 days ago 6
C Question

STM32F103 microcontroller CAN messages

I am wondering if anyone is familiar with any STM32f10x micro-controllers?

If so, I am having some problems configuring a CAN driver. I can run the demo code, which is set to a loop_Back mode, but I cannot get Normal_Mode to work.

I read through all the data sheets, and everything is configured correctly except the INAK in the CAN_MSR register never resets to 0. I can provide more detail if needed, but first I need to know if there is someone who has worked with a STM32F103 microcontroller and CAN messages.

Ron Ron
Answer

You set the Tx pin as Out_PP, but it should be configured as Alternate Function instead. Below is my init code for CAN on an STM32F107. I copy-pasted and stripped it from an existing project so some stuff is not needed (like not all GPIOs need to be enabled). Also note I used the remap function to put the CAN Rx and Tx pins on port D.

This configuration sets the bus speed to 500 kbit/s when using a 72 MHz clock.

Int HardwareInit(void)
{
    Int retval = 0;

    GPIO_InitTypeDef GPIO_InitStructure;
    NVIC_InitTypeDef   NVIC_InitStructure;
    SPI_InitTypeDef SPI_InitStructure;
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;
    ADC_InitTypeDef ADC_InitStructure;
    DMA_InitTypeDef DMA_InitStructure;
    CAN_InitTypeDef        CAN_InitStructure;
    CAN_FilterInitTypeDef  CAN_FilterInitStructure;

    SystemInit();

    /* Enable GPIOs clocks */
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOC |
                           RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOE| RCC_APB2Periph_AFIO, ENABLE);

    /* 2 bit for pre-emption priority, 2 bits for subpriority */
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);


    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO | RCC_APB2Periph_GPIOD, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_CAN1, ENABLE);

    CAN_DeInit(CAN1);
    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 = ENABLE;
    CAN_InitStructure.CAN_RFLM = DISABLE;
    CAN_InitStructure.CAN_TXFP = ENABLE;
    CAN_InitStructure.CAN_Mode = CAN_Mode_Normal;
    CAN_InitStructure.CAN_SJW = CAN_SJW_1tq;
    CAN_InitStructure.CAN_BS1 = CAN_BS1_3tq;
    CAN_InitStructure.CAN_BS2 = CAN_BS2_5tq;
    CAN_InitStructure.CAN_Prescaler = 8;
    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);

    CAN_ITConfig(CAN1, CAN_IT_FMP0, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = CAN1_RX0_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0xFF;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0xFF;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    /* Configure CAN pin: RX */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
    GPIO_Init(GPIOD, &GPIO_InitStructure);

    /* Configure CAN pin: TX */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOD, &GPIO_InitStructure);

    GPIO_PinRemapConfig(GPIO_Remap2_CAN1 , ENABLE);


    return retval;
}

Sending a message can then be done like this:

CanTxMsg TxMessage;
Nat8 mailbox;

TxMessage.StdId = 0x7E5;
TxMessage.RTR=CAN_RTR_DATA;
TxMessage.IDE=CAN_ID_STD;

TxMessage.Data[0] = 0x04;
TxMessage.Data[1] = (state) ? 0x01 : 0x00;
TxMessage.Data[2] = 0x00;
TxMessage.Data[3] = 0x00;
TxMessage.Data[4] = 0x00;
TxMessage.Data[5] = 0x00;
TxMessage.Data[6] = 0x00;
TxMessage.Data[7] = 0x00;
TxMessage.DLC = 8;

do
{
    mailbox = CAN_Transmit(CAN1, &TxMessage);
}
while (mailbox == CAN_NO_MB);

Receiving is done via IRQ:

CanRxMsg rx_message;
CAN_Receive(CAN1, CAN_FIFO0, &rx_message);
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