/*
 * This file is part of the libopencm3 project.
 *
 * Copyright (C) 2013 Frantisek Burian <BuFran@seznam.cz>
 * Copyright (C) 2013-2015 Piotr Esden-Tempski <piotr@esden.net>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <libopencm3/cm3/common.h>
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/f4/rng.h>

static void rcc_setup(void)
{
	rcc_clock_setup_pll(&rcc_hse_8mhz_3v3[RCC_CLOCK_3V3_168MHZ]);

	/* Enable GPIOG clock for onboard leds. */
	rcc_periph_clock_enable(RCC_GPIOG);

	/* Enable rng clock */
	rcc_periph_clock_enable(RCC_RNG);
}

static void rng_setup(void)
{
	/* Enable interupt */
	/* Set the IE bit in the RNG_CR register. */
	RNG_CR |= RNG_CR_IE;
	/* Enable the random number generation by setting the RNGEN bit in
	   the RNG_CR register. This activates the analog part, the RNG_LFSR
	   and the error detector.
	*/
	RNG_CR |= RNG_CR_RNGEN;
}

static void gpio_setup(void)
{
	/* Setup onboard led */
	gpio_mode_setup(GPIOG, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE,
			GPIO13 | GPIO14);
}

/* Tried to folow the guidelines in the stm32f4 user manual.*/
static uint32_t random_int(void)
{
	static uint32_t last_value;
	static uint32_t new_value;

	uint32_t error_bits = 0;
	error_bits = RNG_SR_SEIS | RNG_SR_CEIS;
	while (new_value == last_value) {
		/* Check for error flags and if data is ready. */
		if (((RNG_SR & error_bits) == 0) &&
		    ((RNG_SR & RNG_SR_DRDY) == 1)) {
			new_value = RNG_DR;
		}
	}
	last_value = new_value;
	return new_value;
}


int main(void)
{
	int i, j;
	rcc_setup();
	gpio_setup();
	rng_setup();

	while (1) {
		uint32_t rnd;
		rnd = random_int();

		for (i = 0; i != 32; i++) {
			if ((rnd & (1 << i)) != 0) {
				gpio_set(GPIOG, GPIO13);
			} else {
				gpio_clear(GPIOG, GPIO13);
			}
			/* Delay */
			for (j = 0; j != 5000000; j++) {
				__asm__("nop");
			}
		}
	}
}