examples/platform/stm32/common/STM32WB5MM-DK/Src/entropy_hardware_poll.c

/* USER CODE BEGIN Header */
/**
 ******************************************************************************
 * File Name          : entropy_hardware_poll.c
 * Description        : This file provides code for the entropy collector.
 * author 			  :MCD Application Team
 ******************************************************************************
 * @attention
 *
 * Copyright (c) 2019-2021 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 */

#include "main.h"
#include "stm32wbxx_hal.h"
#include "stm32wbxx_ll_hsem.h"
#include <string.h>

int mbedtls_hardware_poll(void * data, unsigned char * output, size_t len, size_t * olen);

int mbedtls_hardware_poll(void * data, unsigned char * output, size_t len, size_t * olen)
{
    HAL_StatusTypeDef status = HAL_OK;
    uint32_t random_number   = 0;
    /**
     * Static random Address
     * The two upper bits shall be set to 1
     * The lowest 32bits is read from the UDN to differentiate between devices
     * The RNG may be used to provide a random number on each power on
     */
    /* Get RNG semaphore */
    while (LL_HSEM_1StepLock(HSEM, 0))
        ;

    /* Enable RNG */
    __HAL_RNG_ENABLE(&hrng);

    /* Enable HSI48 oscillator */
    LL_RCC_HSI48_Enable();
    /* Wait until HSI48 is ready */
    while (!LL_RCC_HSI48_IsReady())
        ;

    if (HAL_RNG_GenerateRandomNumber(&hrng, &random_number) != HAL_OK)
    {
    }

    /* Disable HSI48 oscillator */
    LL_RCC_HSI48_Disable();

    /* Disable RNG */
    __HAL_RNG_DISABLE(&hrng);

    /* Release RNG semaphore */
    LL_HSEM_ReleaseLock(HSEM, 0, 0);
    ((void) data);
    *olen = 0;

    if ((len < sizeof(uint32_t)) || (HAL_OK != status))
    {
        return 0;
    }

    memcpy(output, &random_number, sizeof(uint32_t));
    *olen = sizeof(uint32_t);

    return 0;
}