100 lines
2.4 KiB
C
100 lines
2.4 KiB
C
/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2013 Frantisek Burian <BuFran@seznam.cz>
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* Copyright (C) 2013-2015 Piotr Esden-Tempski <piotr@esden.net>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <libopencm3/cm3/common.h>
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#include <libopencm3/stm32/rcc.h>
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#include <libopencm3/stm32/gpio.h>
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#include <libopencm3/stm32/f4/rng.h>
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static void rcc_setup(void)
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{
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rcc_clock_setup_hse_3v3(&rcc_hse_8mhz_3v3[RCC_CLOCK_3V3_168MHZ]);
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/* Enable GPIOG clock for onboard leds. */
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rcc_periph_clock_enable(RCC_GPIOG);
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/* Enable rng clock */
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rcc_periph_clock_enable(RCC_RNG);
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}
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static void rng_setup(void)
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{
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/* Enable interupt */
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/* Set the IE bit in the RNG_CR register. */
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RNG_CR |= RNG_CR_IE;
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/* Enable the random number generation by setting the RNGEN bit in
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the RNG_CR register. This activates the analog part, the RNG_LFSR
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and the error detector.
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*/
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RNG_CR |= RNG_CR_RNGEN;
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}
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static void gpio_setup(void)
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{
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/* Setup onboard led */
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gpio_mode_setup(GPIOG, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE,
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GPIO13 | GPIO14);
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}
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/* Tried to folow the guidelines in the stm32f4 user manual.*/
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static uint32_t random_int(void)
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{
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static uint32_t last_value;
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static uint32_t new_value;
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uint32_t error_bits = 0;
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error_bits = RNG_SR_SEIS | RNG_SR_CEIS;
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while (new_value == last_value) {
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/* Check for error flags and if data is ready. */
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if (((RNG_SR & error_bits) == 0) &&
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((RNG_SR & RNG_SR_DRDY) == 1)) {
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new_value = RNG_DR;
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}
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}
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last_value = new_value;
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return new_value;
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}
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int main(void)
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{
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int i, j;
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rcc_setup();
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gpio_setup();
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rng_setup();
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while (1) {
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uint32_t rnd;
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rnd = random_int();
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for (i = 0; i != 32; i++) {
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if ((rnd & (1 << i)) != 0) {
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gpio_set(GPIOG, GPIO13);
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} else {
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gpio_clear(GPIOG, GPIO13);
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}
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/* Delay */
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for (j = 0; j != 5000000; j++) {
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__asm__("nop");
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}
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}
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}
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}
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