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STM32F103C8T6 Blue Pill Not Detected After Flashing MAX31855 SPI Sample Code

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‎2025-01-30 04:49 AM - last edited on ‎2025-01-30 04:55 AM by

Hello STM32 Community,

I am working with an STM32F103C8T6 ("Blue Pill") Original Chip and interfacing it with a MAX31855 thermocouple amplifier over SPI1. I used a sample program generated by ChatGPT, which initializes SPI1 and manually controls the CS pin using MOSI (PA7).

Programmer Used : Original STLINK-V3SET

 

Hello STM32 Community,

I am working with an STM32F103C8T6 ("Blue Pill") and interfacing it with a MAX31855 thermocouple amplifier over SPI1. I used a sample program generated by ChatGPT, which initializes SPI1 and manually controls the CS pin using MOSI (PA7).

Problem Statement:

The program works only on the first flash when I enter debug mode. As soon as i click on Play Button the board stops getting detected via ST-Link/V2 and cannot be reflashed anymore. I have tried with 2-3 different boards, but all of them stopped responding in the same manner.

What I Have Tried:

  1. Checked Hardware Connections:

    • MAX31855 Connections:
      • SCK → PA5
      • DO → PA6 (MISO)
      • CS → PA7 (MOSI, manually controlled)
    • MAX31855 is powered at 3.3V
    • SPI configured in Mode 1 (CPOL = 1, CPHA = 1)

  2. Tried Different Debuggers:

    • Used both ST-Link V3/V2 (clone and original) → No detection after first flash.
    • Tried USB-TTL for Serial Debugging → No response from board.

  3. Checked Boot Modes:

    • Tried Boot0 = 1 (DFU Mode) → No detection in STM32CubeProgrammer.
    • Tried Boot0 = 0 (Normal Mode) → Board still unresponsive.

  4. Tried Different Boards:

    • All boards worked fine initially but stopped working after flashing this particular MAX31855 program.

  5. Power Supply Checks:

    • Measured 3.3V Rail → Voltage remains stable.
    • Checked VDD and NRST Pins → No noticeable issues.

 

 

 

/* 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 */
#define CS_PIN     GPIO_PIN_7  // PA7 (MOSI used as CS)
#define CS_PORT    GPIOA
/* USER CODE END Includes */

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

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
float temperature = 0.0;
/* USER CODE END PD */

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

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
SPI_HandleTypeDef hspi1;

/* USER CODE BEGIN PV */
uint32_t MAX31855_Read(void) {
    uint8_t data[4] = {0, 0, 0, 0};
    uint32_t rawData = 0;

    // Pull CS low (start communication)
    HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_RESET);
    HAL_Delay(1);  // Short delay

    // Read 32-bit data
    HAL_SPI_Receive(&hspi1, data, 4, 100);

    // Pull CS high (end communication)
    HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);

    // Combine bytes into a single 32-bit variable
    rawData = ((uint32_t)data[0] << 24) |
              ((uint32_t)data[1] << 16) |
              ((uint32_t)data[2] <<   |
              ((uint32_t)data[3]);

    return rawData;
}

/**
 * @brief Get temperature from MAX31855.
 */
float MAX31855_GetTemperature(void) {
    uint32_t rawData = MAX31855_Read();

    // Check for fault
    if (rawData & 0x00010000) {
       // printf("Fault detected!\n");
        return -999.0;  // Error value
    }

    // Extract temperature (bits 31-18)
    int16_t tempData = (rawData >> 18) & 0x3FFF;

    // Convert to float (each bit = 0.25°C)
    if (tempData & 0x2000) {  // Check negative sign
        tempData |= 0xC000;  // Sign extend
    }

    return (float)tempData * 0.25;
}
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_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_SPI1_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

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

    /* USER CODE BEGIN 3 */
	  temperature = MAX31855_GetTemperature();
	  HAL_Delay(1000);
  }
  /* USER CODE END 3 */
}

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

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  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_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief SPI1 Initialization Function
  *  None
  * @retval None
  */
static void MX_SPI1_Init(void)
{

  /* USER CODE BEGIN SPI1_Init 0 */

  /* USER CODE END SPI1_Init 0 */

  /* USER CODE BEGIN SPI1_Init 1 */

  /* USER CODE END SPI1_Init 1 */
  /* SPI1 parameter configuration*/
  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES_RXONLY;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_128;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN SPI1_Init 2 */

  /* USER CODE END SPI1_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_GPIOD_CLK_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 */

 

 

 

 

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