STM32 Unique ID – Retrieve Device Electronic Signature

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Overview

In this tutorial, you will learn how to retrieve the STM32 Unique ID, also known as the Device Electronic Signature, using the HAL_GetUID function. This identifier is available on most STM32 MCUs and provides a unique value for each device, although the method may vary slightly across different families.

The STM32 Unique ID is particularly useful when you need to differentiate between multiple boards, such as in client/server applications or distributed systems where each device must be uniquely identified.

The full STM32 Unique ID is 96 bits in length, which can be difficult to manage directly. In many cases, it is useful to reduce this value to a smaller representation, such as 32 bits, using a hashing technique. In this tutorial, we will demonstrate how to scale the 96-bit ID into a more manageable form using a simplified version of the CityHash algorithm, which is included with the provided source code listings.

Below is a list of return values from the HAL_GetUIDwX() function. There are 3 functions available to provide this information:

  • HAL_GetUIDw0();
  • HAL_GetUIDw1();
  • HAL_GetUIDw2();

The following are the return values provided by the above 3 functions:

  • UID[31:0]: X & Y coordinates on the wafer expressed in BCD format
  • UID[39:32]: WAF_NUM[7:0] Wafer number (8-bit unsigned number)
  • UID[63:40]: LOT_NUM[23:0] Lot number (ASCII encoded)
  • UID[95:64]: LOT_NUM[55:24] Lot number (ASCII encoded)
Table Of Contents
  1. Overview
  2. Schematic
  3. Pinouts & Configurations
  4. Code Walkthrough

Schematic

In this particular tutorial, there really isn’t specific hardware settings or a schematic. This tutorial primarily shows the code that is pertinent for gathering and utilizing the Unique Device Serial Information.

Pinouts & Configurations

None of the Pins or Configurations settings really matter in this tutorial. Defaults can be used and that will suffice.

Code Walkthrough

main.h

C
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.h
  * @brief          : Header for main.c file.
  *                   This file contains the common defines of the application.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 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 */

/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __MAIN_H
#define __MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "stm32l4xx_hal.h"

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

/* USER CODE END Includes */

/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */

/* USER CODE END ET */

/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */

/* USER CODE END EC */

/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */

/* USER CODE END EM */

/* Exported functions prototypes ---------------------------------------------*/
void Error_Handler(void);

/* USER CODE BEGIN EFP */

/* USER CODE END EFP */

/* Private defines -----------------------------------------------------------*/

/* USER CODE BEGIN Private defines */

/* USER CODE END Private defines */

#ifdef __cplusplus
}
#endif

#endif /* __MAIN_H */

main.c

The highlighted code is all that is needed to be able to get a hashed uint32_t value of the 96 bits to make it a truly unique and a manageable serial number. This code can be placed into it’s own function, because it is stand-a-lone.

C
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 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"
#include "string.h"
#include "stm32_uidhash.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 ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(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 */
  /* USER CODE BEGIN 2 */

	uint32_t uid[3] = {0x00};
	char buff[12];

	uid[0] = HAL_GetUIDw0();
	uid[1] = HAL_GetUIDw1();
	uid[2] = HAL_GetUIDw2();

	memcpy(&buff[8], &uid[0], 4);
	memcpy(&buff[4], &uid[1], 4);
	memcpy(&buff[0], &uid[2], 4);

	uint32_t uuid = Hash32Len5to12((const char *) &buff, 12);
	
	char hashedUUID[80];
	sprintf(hashedUUID, "0x%8.8lx", uuid);

  /* USER CODE END 2 */

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

    /* 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
  */
  if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
  RCC_OscInitStruct.MSIState = RCC_MSI_ON;
  RCC_OscInitStruct.MSICalibrationValue = 0;
  RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 40;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  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_4) != HAL_OK)
  {
    Error_Handler();
  }
}

/* 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 */

stm32_uidhash.h

C
#ifndef INC_STM32_UIDHASH_H_
#define INC_STM32_UIDHASH_H_

#include "main.h"

uint32_t Hash32Len5to12(const char *s, size_t len);

#endif /* INC_STM32_UIDHASH_H_ */

stm32_uidhash.c

Some of this code was taken from other algorithms, such at MurmurHash Also, special thanks to this site: Generating 32-bit STM32 Unique ID

C
#include <stdio.h>
#include <string.h>

#include "stm32_uidhash.h"

// Magic numbers for 32-bit hashing.  Copied from Murmur3.
static const uint32_t c1 = 0xcc9e2d51;
static const uint32_t c2 = 0x1b873593;

static uint32_t UNALIGNED_LOAD32(const char *p) {
  uint32_t result;
  memcpy(&result, p, sizeof(result));
  return result;
}

static uint32_t Fetch32(const char *p) {
  return UNALIGNED_LOAD32(p);
}

static uint32_t Rotate32(uint32_t val, int shift) {
  // Avoid shifting by 32: doing so yields an undefined result.
  return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
}

// A 32-bit to 32-bit integer hash copied from Murmur3.
static uint32_t fmix(uint32_t h)
{
  h ^= h >> 16;
  h *= 0x85ebca6b;
  h ^= h >> 13;
  h *= 0xc2b2ae35;
  h ^= h >> 16;
  return h;
}

static uint32_t Mur(uint32_t a, uint32_t h) {
  // Helper from Murmur3 for combining two 32-bit values.
  a *= c1;
  a = Rotate32(a, 17);
  a *= c2;
  h ^= a;
  h = Rotate32(h, 19);
  return h * 5 + 0xe6546b64;
}

uint32_t Hash32Len5to12(const char *s, size_t len) {
  uint32_t a = (uint32_t)len, b = a * 5, c = 9, d = b;
  a += Fetch32(s);
  b += Fetch32(s + len - 4);
  c += Fetch32(s + ((len >> 1) & 4));
  return fmix(Mur(c, Mur(b, Mur(a, d))));
}

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