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77 lines
1.8 KiB
C
77 lines
1.8 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser General
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* Public License v2.1. See the file LICENSE in the top level directory for more
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* details.
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*/
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/**
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* @ingroup driver_periph
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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/random.h"
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/* only compile this driver if enabled in the board's periph_conf.h */
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#if RANDOM_NUMOF
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/**
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* @name KEY needs to be written to the config register when en|disabling
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* random number generation
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*/
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#define KEY (0x524e4700)
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void random_init(void)
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{
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random_poweron();
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}
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int random_read(char *buf, unsigned int num)
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{
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/* cppcheck-suppress variableScope */
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uint32_t tmp;
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int count = 0;
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while (count < num) {
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/* wait until new value is generated -> takes up to 84 cycles */
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while (!(TRNG->TRNG_ISR & TRNG_ISR_DATRDY));
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/* read 4 byte of random data */
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tmp = TRNG->TRNG_ODATA;
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/* extract copy bytes to result */
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for (int i = 0; i < 4 && count < num; i++) {
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buf[count++] = (char)tmp;
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tmp = tmp >> 8;
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}
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}
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return count;
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}
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void random_poweron(void)
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{
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/* enable clock signal for TRNG module */
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PMC->PMC_PCER1 |= PMC_PCER1_PID41;
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/* enable the generation of random numbers */
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TRNG->TRNG_CR |= (KEY | TRNG_CR_ENABLE);
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}
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void random_poweroff(void)
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{
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/* disable the generation of random numbers */
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TRNG->TRNG_CR &= ~(KEY | TRNG_CR_ENABLE);
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/* disable clock signal for TRNG module */
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PMC->PMC_PCER1 &= ~(PMC_PCER1_PID41);
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}
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#endif /* RANDOM_NUMOF */
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