Posted on October 19, 2017 at 11:11
(note this is my first question on ST community If I can do anything to improve the question, please let me know).
Setup
I am using an STM32F103C8T6 (aka Blue Pill).
With the STM32Cube I set CAN_RX to PB8 and CAN_TX9 to PB9 (these are defaults/nonchangeable).
The generated CAN settings are:
hcan.Instance = CAN1;
hcan.Init.Prescaler = 16;
hcan.Init.Mode = CAN_MODE_NORMAL;
hcan.Init.SJW = CAN_SJW_1TQ;
hcan.Init.BS1 = CAN_BS1_4TQ;
hcan.Init.BS2 = CAN_BS2_5TQ;
hcan.Init.TTCM = DISABLE;
hcan.Init.ABOM = DISABLE;
hcan.Init.AWUM = DISABLE;
hcan.Init.NART = DISABLE;
hcan.Init.RFLM = DISABLE;
hcan.Init.TXFP = DISABLE;�?�?�?�?�?�?�?�?�?�?�?�?
Program
(removed STM HAL generated comments blocks)
int main(void)
{
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_CAN_Init();
/* USER CODE BEGIN 2 */
hcan.pRxMsg = &_rxMessage;
hcan.pTxMsg = &_txMessage;
_sFilterConfig.FilterActivation = ENABLE;
_sFilterConfig.FilterNumber = 0;
_sFilterConfig.FilterMode = CAN_FILTERMODE_IDMASK;
_sFilterConfig.FilterScale = CAN_FILTERSCALE_32BIT;
_sFilterConfig.FilterIdHigh = 0x0000;
_sFilterConfig.FilterIdLow = 0x0000;
_sFilterConfig.FilterMaskIdHigh = 0x0000;
_sFilterConfig.FilterMaskIdLow = 0x0000;
_sFilterConfig.FilterFIFOAssignment = 0;
_sFilterConfig.BankNumber = 14;
if (HAL_CAN_ConfigFilter(&hcan, &_sFilterConfig) != HAL_OK)
{
Error_Handler();
}
hcan.pTxMsg->StdId = 0x321;
hcan.pTxMsg->ExtId = 0x01;
hcan.pTxMsg->RTR = CAN_RTR_DATA;
hcan.pTxMsg->IDE = CAN_ID_STD;
hcan.pTxMsg->DLC = 2;
hcan.pTxMsg->Data[0] = 0;
while (1)
{
hcan.pTxMsg->Data[0]++;
if (HAL_CAN_Transmit(&hcan, 10) != HAL_OK)
{
Error_Handler();
}
HAL_Delay(1000);
if (HAL_CAN_Receive_IT(&hcan, CAN_FIFO0) != HAL_OK)
{
Error_Handler();
}
}
}�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
Loopback mode
When I use loopback mode:
hcan.Init.Mode = CAN_MODE_LOOPBACK
instead of Normal mode, I can transmit and receive messages (and the hcan shows the correct data in the received message).
Problem
However, in Normal mode (as shown in the code fragment above) I always get a timeout in the next command:
if (HAL_CAN_Transmit(&hcan, 10) != HAL_OK)
The function returns: HAL_CAN_STATE_TIMEOUT
All initialization seems to be ok (all functions return HAL_OK).
Analysis
What I tried was:
- Using another STM32: no difference
- Using another transceiver: no difference
- Played a bit with the SJW/BS1/BS2 time quantities: no difference
- Making sure the time quantities were equal
- Playing with different data values and filters: no difference
- Checked the output of PB9 (CAN transmit): it seems not to change at all (so this is a problem): no difference
- Removing the wire from GPIO PB9 (CAN Tx) to the TX of my CAN transceiver : no difference.
- Checking the Transmit is cancelled (which is needed and was an old bug, but has already been fixed by the HAL library I'm using).
Observations
- ESR is 111110000000000001010111, which means LEC[2:0] (see [Reference manual, page 682][1]), is 101 which is Bit dominant error
- BTR is 11101010000000001001111, which means bit 30 LKBM: Loop back Mode (debug) is 1, which is strange because in the setup I assigned CAN_MODE_NORMAL.
- Directly after the command, the State is HAL_CAN_STATE_TIMEOUT, the Lock is HAL_UNLOCKED, the ErrorCode is 0.
Questions
1. Why do I get a timeout? I'm having a hard time trying to find more to check what I already did. What bothers me is that the PB9 GPIO does not change, so I'm sure it's a software problem, but since there is no error code (it's 0) and initialization is OK, I'm getting out of clues.
Related question:
2. Am I in loopback mode or not (according to the Setup I put CAN_MODE_NORMAL, but the BTR bit 30: LKBM shows otherwise.
[1]:
http://www.st.com/content/ccc/resource/technical/document/reference_manual/59/b9/ba/7f/11/af/43/d5/CD00171pdf/files/CD00171pdf/jcr:content/translations/en.CD00171pdf
#can #stm32f103 #stm32cube
