STM32F303VET - issue in transmitting CAN messages

[GComes]

I am having an issue in transmitting CAN messages, my situation is the following:

There is an interrupt function for RX messages from CAN1, when a message is received, it sets a flag. 

The baud rate of the RX message is 10ms and they are being sent over the software PCAN.

struct
{
	volatile uint8_t transmit_data;
}Flags;



void can1_RxCallback()
{
	Flags.transmit_data = 1;
}

In the main function in the while-loop, this flag is compared, if it is high, it executes a code to transmit data over CAN-Bus.

	
while (1)
{
	if (1 == Flags.transmit_data)
	{
		tx_data();
	}
}

void tx_data(void)
{	
     //delay(1);  //Non interrupt delay in ms
	can_transmit(&can, CanMessObj[nr].MessageID, 0, (uint8_t *)CANTrxBuffer[nr].Data, CanMessObj[nr].Length);		
	Flags.transmit_data = 0; //Reset Flag
}


void can_transmit(can_Interface_t* canInterface, uint32_t Id, uint32_t ide, uint8_t data[8], uint8_t length)
{
	uint32_t mailbox;
	canInterface->txMsg.IDE = ide;
	canInterface->txMsg.StdId = Id;
	canInterface->txMsg.ExtId = Id;
	canInterface->txMsg.DLC = length;
	
	HAL_CAN_AddTxMessage(canInterface->canChannel, &canInterface->txMsg, data, &mailbox);
}

The issue is some TX messages are not being sent, however, when I add the 1 ms delay, it works perfectly. But I want to avoid using delay.

So, to understand if the problem was in the transmission baud rate, I implemented a Timer interrupt for each 1ms and set the flag there instead of in the CAN interrupt and commented out the "delay(1)" in the function tx_data().

In this configuration, all TX messages were sent correctly.

void TIM7_IRQHandler(void) 
{	
	Flags.transmit_data = 1;
}

As the Timer interrupt is 10x faster than the CAN interrupt, I concluded that the issue is not how often the CAN messages are being transmitted. However, at the current point, I have no idea what could be leading to this issue, basically, I just changed where the flag is being set, nothing else.

Someone could help me to understand what might be causing this issue for transmitting?
CAN baud rate is: 250Kb

MCU: STM32F303VET

For checking the CAN messages and transmitting the CAN messages to the MCU I am using the software PCAN

[SofLit]

Hello,

What is the status returned by HAL_CAN_AddTxMessage() ?

PS: there is no STM32F30EVET part number. Please check.

[GComes]

Hi @SofLit , thank you for the answer.

I updated the part number, the correct one is STM32F303VET.

The return from HAL_CAN_AddTxMessage() is always "HAL_OK"

[SofLit]

OK, 

Try to check for free Tx mailbox before sending:

uint32_t freeTxMbox;
.
.
do
{
  freeTxMbox = HAL_CAN_GetTxMailboxesFreeLevel(canInterface->canChannel);
}while(freeTxMbox == 0);
HAL_CAN_AddTxMessage(canInterface->canChannel, &canInterface->txMsg, data, &mailbox);

[GComes]

Hi @SofLit , the result is still the same.

Meanwhile, I was doing another test, I sent two TX messages, instead of one, as shown below:

void tx_data(void)
{	
     //delay(1);  //Non interrupt delay in ms
	can_transmit(&can, CanMessObj[1].MessageID, 0, (uint8_t *)CANTrxBuffer[1].Data, CanMessObj[1].Length);	
	can_transmit(&can, CanMessObj[2].MessageID, 0, (uint8_t *)CANTrxBuffer[2].Data, CanMessObj[2].Length);		
	Flags.transmit_data = 0; //Reset Flag
}

Adding the code sample you provided the first message CanMessObj[1] missed some messages, while the CanMessObj[2] sent all them.

In PCAN-View I had the following result

                          |   ID    |  Length  |    Count
CanMessObj[1] | 0x30  |      8       |      464

CanMessObj[2] | 0x31  |      6       |      1096 


Setting the flag in the Timer interrupt or adding the 1 ms delay, the counter for both messages was the same. 

[Karl Yamashita · Accepted solution]

Do you have Automatic Retransmission enabled?

[GComes]

Hi @Karl Yamashita

It was disabled. I have enabled it and it is working. Thank you!

[Karl Yamashita]

You're welcome. Glad you got it working.