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/*
* Copyright (C) 2014-2016 Freie Universitรคt Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu_stm32f4
* @{
*
* @file
* @brief Low-level random number generator driver implementation
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include "cpu.h"
#include "periph_conf.h"
#include "periph/hwrng.h"
/* only build if the CPU actually provides a RNG peripheral */
#ifdef RNG
void hwrng_init(void)
{
/* no need for initialization */
}
void hwrng_read(uint8_t *buf, unsigned int num)
{
unsigned int count = 0;
/* power on and enable the device */
periph_clk_en(AHB2, RCC_AHB2ENR_RNGEN);
RNG->CR = RNG_CR_RNGEN;
/* get random data */
while (count < num) {
/* wait for random data to be ready to read */
while (!(RNG->SR & RNG_SR_DRDY)) {}
/* read next 4 bytes */
uint32_t tmp = RNG->DR;
/* copy data into result vector */
for (int i = 0; i < 4 && count < num; i++) {
buf[count++] = (uint8_t)tmp;
tmp = tmp >> 8;
}
}
/* finally disable the device again */
RNG->CR = 0;
periph_clk_dis(AHB2, RCC_AHB2ENR_RNGEN);
}
#endif /* CPUID_LEN */
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