STM32H7S3L8H6 NUCLEO SPI Loopback Test Failing

shri7 · ‎2025-12-05

I’ve been trying to run an SPI loopback test, but my code gets stuck in the transmit function. The data never actually transmits, so the function waits indefinitely. When I checked the SPI clock pin with a logic analyzer, it remains low. I also verified the peripheral clock in the SFRs, and it shows that the SPI clock is enabled.

For the hardware setup, I connected MOSI to MISO with a jumper wire.

I’ve attached images and included the full code—please take a look and help me figure out what’s causing the issue. One more note: I’ve used the same configuration in previous projects and it worked fine, but now it suddenly doesn’t.

If the information I’ve provided isn’t clear or sufficient, I apologize—please let me know, and I can share more details.

/* 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 */
#include<stdio.h>
/* 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 ---------------------------------------------------------*/

SPI_HandleTypeDef hspi3;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
static void MX_GPIO_Init(void);
static void MX_SPI3_Init(void);
/* USER CODE BEGIN PFP */
uint8_t tx = 0xA5;
uint8_t rx = 0;


/* 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--------------------------------------------------------*/

  /* Update SystemCoreClock variable according to RCC registers values. */
  SystemCoreClockUpdate();

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

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_SPI3_Init();
  /* USER CODE BEGIN 2 */
  HAL_SPI_TransmitReceive(&hspi3, &tx, &rx, sizeof(tx), HAL_MAX_DELAY);

  HAL_Delay(1);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13, GPIO_PIN_SET);
	  HAL_Delay(1000);
	  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_7, GPIO_PIN_SET);
  }
  /* USER CODE END 3 */
}

/**
  * @brief SPI3 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_SPI3_Init(void)
{

  /* USER CODE BEGIN SPI3_Init 0 */

  /* USER CODE END SPI3_Init 0 */

  /* USER CODE BEGIN SPI3_Init 1 */

  /* USER CODE END SPI3_Init 1 */
  /* SPI3 parameter configuration*/
  hspi3.Instance = SPI3;
  hspi3.Init.Mode = SPI_MODE_MASTER;
  hspi3.Init.Direction = SPI_DIRECTION_2LINES;
  hspi3.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi3.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi3.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi3.Init.NSS = SPI_NSS_SOFT;
  hspi3.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_32;
  hspi3.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi3.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi3.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi3.Init.CRCPolynomial = 0x7;
  hspi3.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;
  hspi3.Init.NSSPolarity = SPI_NSS_POLARITY_LOW;
  hspi3.Init.FifoThreshold = SPI_FIFO_THRESHOLD_01DATA;
  hspi3.Init.MasterSSIdleness = SPI_MASTER_SS_IDLENESS_00CYCLE;
  hspi3.Init.MasterInterDataIdleness = SPI_MASTER_INTERDATA_IDLENESS_00CYCLE;
  hspi3.Init.MasterReceiverAutoSusp = SPI_MASTER_RX_AUTOSUSP_DISABLE;
  hspi3.Init.MasterKeepIOState = SPI_MASTER_KEEP_IO_STATE_DISABLE;
  hspi3.Init.IOSwap = SPI_IO_SWAP_DISABLE;
  hspi3.Init.ReadyMasterManagement = SPI_RDY_MASTER_MANAGEMENT_INTERNALLY;
  hspi3.Init.ReadyPolarity = SPI_RDY_POLARITY_HIGH;
  if (HAL_SPI_Init(&hspi3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN SPI3_Init 2 */

  /* USER CODE END SPI3_Init 2 */

}

/**
  * @brief GPIO Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  /* USER CODE BEGIN MX_GPIO_Init_1 */

  /* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_7, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13, GPIO_PIN_RESET);

  /*Configure GPIO pin : PB7 */
  GPIO_InitStruct.Pin = GPIO_PIN_7;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /*Configure GPIO pin : PD13 */
  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  /* 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.
  * @PAram  file: pointer to the source file name
  * @PAram  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 */

TDK · ‎2025-12-05

> When I checked the SPI clock pin with a logic analyzer, it remains low.

This will prevent SPI from working.

Initialize the SPI SCK pin as GPIO output and toggle it. Verify on a scope that it toggles.

If it isn't able to toggle, probably it is being tied low somewhere in your hardware. This is likely a hardware problem, not software.

Other possibilities are that you are not monitoring the pin you think you are, or you are not initializing the pin you think you are.

If you feel a post has answered your question, please click "Accept as Solution".

shri7 · ‎2025-12-05

Yes,The pin toggles even tried using a different spi