[stm32f429i-discovery] Added random blinking example.

examples/stm32/f4/stm32f429i-discovery/random/Makefile

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+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+##
+## 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/>.
+##
+
+BINARY = random
+
+LDSCRIPT = ../stm32f429i-discovery.ld
+
+include ../../Makefile.include
+

examples/stm32/f4/stm32f429i-discovery/random/README

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+------------------------------------------------------------------------------
+README
+------------------------------------------------------------------------------
+
+This example randomly blinks the GREEN LED on the ST STM32F429IDISCOVERY eval
+board.
+
+Board connections:
+------------------
+
+ <none required>
+

examples/stm32/f4/stm32f429i-discovery/random/random.c

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+/*
+ * This file is part of the libopencm3 project.
+ *
+ * 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_hse_3v3(&hse_8mhz_3v3[CLOCK_3V3_120MHZ]);
+
+	/* 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");
+			}
+		}
+	}
+}