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/Makefile

@@ -0,0 +1,16 @@
+KNOWN_EXAMPLES = gpio-output
+
+ifneq ($(filter $(EXAMPLE),$(KNOWN_EXAMPLES)),)
+  CONTIKI_PROJECT = $(EXAMPLE)
+else
+  CONTIKI_PROJECT = help
+endif
+
+all: $(CONTIKI_PROJECT)
+
+CONTIKI = ../..
+include $(CONTIKI)/Makefile.include
+
+help:
+	@echo -e "\nSet the variable EXAMPLE to one of the following Galileo-specific examples:"
+	@for EXAMPLE in $(KNOWN_EXAMPLES); do echo $$EXAMPLE; done

examples/galileo/README

@@ -0,0 +1,25 @@
+Galileo Specific Examples
+=======================
+
+This directory contains galileo-specific example applications to illustrate
+how to use galileo APIs.
+
+In order to build a application, you should set the EXAMPLE environment
+variable to the name of the application you want to build. For instance, if
+you want to build gpio-output application, run the following command:
+$ make TARGET=galileo EXAMPLE=gpio-output
+
+============
+=   GPIO   =
+============
+
+GPIO Output
+===========
+
+This application shows how to use the GPIO driver APIs to manipulate output
+pins. This application sets the GPIO 4 pin as output pin and toggles its
+state at every half second.
+
+For a visual effect, you should wire shield pin IO1 to a led in a protoboard.
+Once the application is running, you should see a blinking LED.
+

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();
+}