galileo: Add GPIO output example

This patch introduces an example application to demonstrate how to use
GPIO driver APIs to manipulate output pins. The application sets the
GPIO 4 pin as output pin and toggles its state at every half second.

examples/galileo/gpio-output.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2015, Intel Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+
+#include "contiki.h"
+#include "sys/ctimer.h"
+
+#include "gpio.h"
+
+#define PIN 4 /* IO1 */
+
+static uint32_t value;
+static struct ctimer timer;
+
+PROCESS(gpio_output_process, "GPIO Output Process");
+AUTOSTART_PROCESSES(&gpio_output_process);
+/*---------------------------------------------------------------------------*/
+static void
+timeout(void *data)
+{
+  /* toggle pin state */
+  value = !value;
+  quarkX1000_gpio_write(PIN, value);
+
+  ctimer_reset(&timer);
+}
+/*---------------------------------------------------------------------------*/
+PROCESS_THREAD(gpio_output_process, ev, data)
+{
+  PROCESS_BEGIN();
+
+  quarkX1000_gpio_init();
+  quarkX1000_gpio_config(PIN, QUARKX1000_GPIO_OUT);
+
+  quarkX1000_gpio_clock_enable();
+
+  ctimer_set(&timer, CLOCK_SECOND / 2, timeout, NULL);
+
+  printf("GPIO output example is running\n");
+  PROCESS_YIELD();
+
+  quarkX1000_gpio_clock_disable();
+
+  PROCESS_END();
+}