How to get FDCAN working on STM32G0B1 microcontrollers

[adarsh_k_96]

I have an STM32G0B1CBT6 board and am trying to get CANFD / FDCAN working. I have STM32CubeIDE code that works, but I am unable to get it to work with Arduino. Here is my code; any help is appreciated.

CubeIDE code

/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2025 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
FDCAN_HandleTypeDef hfdcan1;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_FDCAN1_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/* MCU Configuration--------------------------------------------------------*/

/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();

/* USER CODE BEGIN Init */

/* USER CODE END Init */

/* Configure the system clock */
SystemClock_Config();

/* USER CODE BEGIN SysInit */

/* USER CODE END SysInit */

/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_FDCAN1_Init();
/* USER CODE BEGIN 2 */

if (HAL_FDCAN_Start(&hfdcan1) != HAL_OK) {
Error_Handler();
}


/* USER CODE END 2 */

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
HAL_Delay(1000);
/* USER CODE END WHILE */
FDCAN_TxHeaderTypeDef TxHeader;
uint8_t TxData[8] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88};

TxHeader.Identifier = 0x321;
TxHeader.IdType = FDCAN_STANDARD_ID;
TxHeader.TxFrameType = FDCAN_DATA_FRAME;
TxHeader.DataLength = FDCAN_DLC_BYTES_8;
TxHeader.ErrorStateIndicator = FDCAN_ESI_ACTIVE;
TxHeader.BitRateSwitch = FDCAN_BRS_OFF;
TxHeader.FDFormat = FDCAN_CLASSIC_CAN;
TxHeader.TxEventFifoControl = FDCAN_NO_TX_EVENTS;
TxHeader.MessageMarker = 0;

if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, TxData) != HAL_OK) {
Error_Handler();
} else {

}

/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}

/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

/** Configure the main internal regulator output voltage
*/
HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);

/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV1;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}

/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;

if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
}

/**
* @brief FDCAN1 Initialization Function
*  None
* @retval None
*/
static void MX_FDCAN1_Init(void)
{

/* USER CODE BEGIN FDCAN1_Init 0 */

/* USER CODE END FDCAN1_Init 0 */

/* USER CODE BEGIN FDCAN1_Init 1 */

/* USER CODE END FDCAN1_Init 1 */
hfdcan1.Instance = FDCAN1;
hfdcan1.Init.ClockDivider = FDCAN_CLOCK_DIV1;
hfdcan1.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;
hfdcan1.Init.AutoRetransmission = ENABLE;
hfdcan1.Init.TransmitPause = DISABLE;
hfdcan1.Init.ProtocolException = DISABLE;
hfdcan1.Init.NominalPrescaler = 2; //hfdcan1.Init.NominalPrescaler = 4;
hfdcan1.Init.NominalSyncJumpWidth = 1;
hfdcan1.Init.NominalTimeSeg1 = 13;
hfdcan1.Init.NominalTimeSeg2 = 2;
hfdcan1.Init.DataPrescaler = 1;
hfdcan1.Init.DataSyncJumpWidth = 1;
hfdcan1.Init.DataTimeSeg1 = 1;
hfdcan1.Init.DataTimeSeg2 = 1;
hfdcan1.Init.StdFiltersNbr = 0;
hfdcan1.Init.ExtFiltersNbr = 0;
hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN FDCAN1_Init 2 */

/* USER CODE END FDCAN1_Init 2 */

}

/**
* @brief GPIO Initialization Function
*  None
* @retval None
*/
static void MX_GPIO_Init(void)
{
/* USER CODE BEGIN MX_GPIO_Init_1 */

/* USER CODE END MX_GPIO_Init_1 */

/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOA_CLK_ENABLE();

/* USER CODE BEGIN MX_GPIO_Init_2 */

/* USER CODE END MX_GPIO_Init_2 */
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}

#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
*  file: pointer to the source file name
*  line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

Arduino Code

#include "stm32g0xx_hal.h"
#include "stm32g0xx_hal_fdcan.h"

FDCAN_HandleTypeDef hfdcan1;
FDCAN_HandleTypeDef* phfdcan1 = &hfdcan1;
FDCAN_HandleTypeDef* phfdcan2 = nullptr;

void My_Error_Handler(){
while(1){};
}

void MX_FDCAN1_Init() {
hfdcan1.Instance = FDCAN1;
hfdcan1.Init.ClockDivider = FDCAN_CLOCK_DIV1;
hfdcan1.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;
hfdcan1.Init.AutoRetransmission = ENABLE;
hfdcan1.Init.TransmitPause = DISABLE;
hfdcan1.Init.ProtocolException = DISABLE;
hfdcan1.Init.NominalPrescaler = 2;
hfdcan1.Init.NominalSyncJumpWidth = 1;
hfdcan1.Init.NominalTimeSeg1 = 13;
hfdcan1.Init.NominalTimeSeg2 = 2;
hfdcan1.Init.DataPrescaler = 1;
hfdcan1.Init.DataSyncJumpWidth = 1;
hfdcan1.Init.DataTimeSeg1 = 1;
hfdcan1.Init.DataTimeSeg2 = 1;
hfdcan1.Init.StdFiltersNbr = 0;
hfdcan1.Init.ExtFiltersNbr = 0;
hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;

if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK) {
My_Error_Handler();
}
}

void setup() {
HAL_Init();
MX_FDCAN1_Init();

if (HAL_FDCAN_Start(&hfdcan1) != HAL_OK) {
My_Error_Handler();
}
}

void loop() {
delay(1000);

FDCAN_TxHeaderTypeDef TxHeader;
uint8_t TxData[8] = { 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88 };

TxHeader.Identifier = 0x321;
TxHeader.IdType = FDCAN_STANDARD_ID;
TxHeader.TxFrameType = FDCAN_DATA_FRAME;
TxHeader.DataLength = FDCAN_DLC_BYTES_8;
TxHeader.ErrorStateIndicator = FDCAN_ESI_ACTIVE;
TxHeader.BitRateSwitch = FDCAN_BRS_OFF;
TxHeader.FDFormat = FDCAN_CLASSIC_CAN;
TxHeader.TxEventFifoControl = FDCAN_NO_TX_EVENTS;
TxHeader.MessageMarker = 0;

if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, TxData) != HAL_OK) {
My_Error_Handler();
}
}

[mƎALLEm]

Hello @adarsh_k_96 and welcome to the ST community,

---

@adarsh_k_96 wrote:

I have an STM32G0B1CBT6 board 

---

STM32G0B1CBT6 is a MCU not an board. So what board are you using? ST board? custom board? please show image of the board or a link to an image of it. What do you mean by "is not working?"

Are you establishing a complete CAN bus with two nodes and each one having a CAN transceiver?

[adarsh_k_96]

I should have been more specific.
I'm using a custom board with the mentioned microcontroller and a TJA1051 CAN transceiver connected to pins PA12 and PA11. The board uses the internal clock since there's no external crystal. Currently, no other CAN nodes are connected. I'm monitoring the pin states with a logic analyzer. When I run the code using CubeIDE, I see changes on the pins, but when I run the Arduino code, the pins remain inactive, even though the MCU is running and successfully toggling an LED.

[mƎALLEm · Accepted solution]

Hello,

---

@adarsh_k_96 wrote:

Currently, no other CAN nodes are connected. I'm monitoring the pin states with a logic analyzer. 

---

Hello,

You cannot do that in Normal mode.

hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;

This is the minimum hardware required to establish a CAN bus:

You need at least another node on the bus for the acknowledgement mechanism. CAN is not UART or SPI to use it in stand alone.

Use External loopback mode instead, where you can use one node in stand alone and monitor the Tx pin.

Hope that helps.

[adarsh_k_96]

But why does it work when I run the code in CubeIDE, which also uses FDCAN normal mode? I can see the pin toggling, and the logic analyzer shows the correct values. On the other hand, with the Arduino code, the pin doesn't even switch at all.

I'm not concerned about the ACK bit or whether the transmission is successful/acknowledged — I just want some activity on that pin so I can take from there.

The main issue is that there's no toggling happening on the pin in the Arduino setup.

[mƎALLEm]

I don't know how you judjed it's working with CubeIDE and what kind of test you did. You cannot use Normal mode in stand alone. Please use loopback mode instead. For Arduino environment question you can contact them on their forums: https://forum.arduino.cc/

The acknowledge bit is set by hardware when a node receives a correct frame. You don't have to set any bit. But in normal mode the acknowledgement bit is sent by the receiver, since you don't have a receiver on the bus, the acknowledgement mechanism is broken. That's why you cannot use Normal mode in your situation.