STM32F103 microcontroller CAN messages - c++

Question

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.

Answer 1

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);

Answer 2

I've worked with STM32F103 microcontrollers but my only (small) experience with CAN was that enabling it caused USB not to work. The two modules share a memory space. So make sure you disable the USB module and the clock to it (clear bit 23 of RCC_APB1ENR).