LCD version of the Mandelbrot example

This version is the ASCII one but uses the LCD display
that is attached to the board for a more colorful result.

This example also zooms into a more "interesting" place in the set so
the display stays interesting during the full 100 generations.

examples/stm32/f4/stm32f429i-discovery/mandelbrot-lcd/clock.c

@@ -0,0 +1,88 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+ * Copyright (C) 2011 Stephen Caudle <scaudle@doceme.com>
+ * Copyright (C) 2012 Daniel Serpell <daniel.serpell@gmail.com>
+ * Copyright (C) 2015 Piotr Esden-Tempski <piotr@esden.net>
+ * Copyright (C) 2015 Chuck McManis <cmcmanis@mcmanis.com>
+ *
+ * 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 <stdio.h>
+#include <ctype.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/cm3/systick.h>
+#include <libopencm3/cm3/nvic.h>
+#include "clock.h"
+
+void clock_setup(void)
+{
+	rcc_clock_setup_hse_3v3(&hse_8mhz_3v3[CLOCK_3V3_168MHZ]);
+
+	/* set up the SysTick function (1mS interrupts) */
+	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
+	STK_CVR = 0;
+	systick_set_reload(rcc_ahb_frequency / 1000);
+	systick_counter_enable();
+	systick_interrupt_enable();
+}
+
+/* simple millisecond counter */
+static volatile uint32_t system_millis;
+static volatile uint32_t delay_timer;
+
+/*
+ * Simple systick handler
+ *
+ * Increments a 32 bit value once per millesecond
+ * which rolls over every 49 days.
+ */
+void sys_tick_handler(void)
+{
+	system_millis++;
+	if (delay_timer > 0) {
+		delay_timer--;
+	}
+}
+
+/*
+ * Simple spin loop waiting for time to pass
+ *
+ * A couple of things to note:
+ * First,  you can't just compare to
+ * system_millis because doing so will mean
+ * you delay forever if you happen to hit a
+ * time where it is rolling over.
+ * Second, accuracy is "at best" 1mS as you
+ * may call this "just before" the systick hits
+ * with a value of '1' and it would return
+ * nearly immediately. So if you need really
+ * precise delays, use one of the timers.
+ */
+void
+msleep(uint32_t delay)
+{
+	delay_timer = delay;
+	while (delay_timer);
+}
+
+uint32_t
+mtime(void)
+{
+	return system_millis;
+}