Electronic – STM32 HAL CAN does not update value and crashes when setting ExtId

candebuggingstm32variable

I'm running my first CAN test program using STM32CubeMX, STM32F103C8T6 and Eclipse.

I used default CAN settings in STM32CubeMX (also tried loopback but the results are equal).

What I see (see pic below) is two things I do not understand;

In the picture below, you can see I exceeded the line with hcan.pTxMsg->StdId = 0x321 (left red oval), but the current value shows 536891392 (right red oval).
When I execute the next line (green): hcan.pTxMsg->ExtId = 0x01, I end up in a hard fault interrupt:

/**
- @brief This function handles Hard fault interrupt.
  /
  void HardFault_Handler(void)
  {
  / USER CODE BEGIN HardFault_IRQn 0 */
  
  /* USER CODE END HardFault_IRQn 0 /
  while (1)
  {
  }
  / USER CODE BEGIN HardFault_IRQn 1 */
  
  /* USER CODE END HardFault_IRQn 1 */
  }

Why is the value not updated and why do I get a hardware fault (the pointer hcan.pTxMsg is not NULL since it even displays the field StdId (it even can display ExtId which has value 134222077 (not shown in pic below)?

Best Answer

By default STM32CubeMx create the initialization code for 'can' (if selected). This code can be found in MX_CAN_Init and is called by main.

However, it does not assign/initialize the pRxMsg and pTxMsg.

The pTxMsg should be defined as:

CanTxMsgTypeDef txMessage;
hcan.pTxMsg = &txMessage;

and the pRxMsg as:

CanRxMsgTypeDef rxMessage;
hcan.pRxMsg = &rxMessage;

Related Solutions

Electronic – STM32 DMA Transfer bridge between 2 uart ports

Consider the following snippet from the STM32F1 manual regarding the USART data register and its corresponding status bit 'TXE':

Single byte communication

The TXE bit is always cleared by a write to the data register. The TXE bit is set by hardware and it indicates:

• The data has been moved from TDR to the shift register and the data transmission has started.

• The TDR register is empty.

• The next data can be written in the USART_DR register without overwriting the previous data.

This flag generates an interrupt if the TXEIE bit is set.

Can you imagine a scenario where you are writing into the data register before the previous byte has made it into the shift register? Think about the sequence of events when you receive a stream of bytes, especially when you receive the third or fourth byte, what is your transmitter doing at this point? Is its data register occupied?

As a previous comment mentioned, you likely need a way to buffer previous byte(s) if the TXE status bit is not set. Writing into the USART data register while the TXE status bit is not set is a guaranteed way to lose information.

Edit in response to comment:

That's one way to do it, I would imagine it would work. However, I think doing away with DMA and using the USART interrupts would be a better approach. You can have 2 interrupt service routines for when a byte is received and when the transmit data register is empty. Based on those two events, you can decide to buffer the data (in the RX handler) and to empty the buffer (in TX complete handler). Care must be taken in deciding when to enable/disable the TX complete interrupt. I think the overhead of setting up DMA makes more sense for larger sequential transactions into (or out of) buffers, and less so for the single byte-by-byte case.

Electronic – STM32 HAL_CAN_Transmit always returns TIMEOUT (HAL_CAN_STATE_TIMEOUT)

I got the new version and what a difference there are quite a couple of changes to keep in mind so here are some snippets:


// To send a message
// Old version:
HAL_CAN_Transmit(&hcan1, 10);

//new version:
HAL_CAN_AddTxMessage(&hcan, &TxMessage, TxData, &TxMailbox); 

//To receive a message by polling
        Receive_CAN_Message_Polling(RxMessage, RxData);     

// here is the Polling Function 

void Receive_CAN_Message_Polling(CAN_RxHeaderTypeDef RxMessage_, uint8_t* RxData_){
    uint8_t messages = HAL_CAN_GetRxFifoFillLevel(&hcan, CAN_RX_FIFO0);
        if(messages > 0){
            if(HAL_CAN_GetRxMessage(&hcan, CAN_RX_FIFO0, &RxMessage_, RxData_) == HAL_OK){
            Indicate();             
        }
    }
}

much different to the old Library but it works very well I have not yet looked at the Interrupts and receiving with them but I am sure that they also work fine in the new version of the HAL_CAN Driver

Best Answer

Related Solutions

Electronic – STM32 DMA Transfer bridge between 2 uart ports

Electronic – STM32 HAL_CAN_Transmit always returns TIMEOUT (HAL_CAN_STATE_TIMEOUT)

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