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