/**
 * \file
 *
 * \brief SAM D20 External Interrupt Driver Quick Start
 *
 * Copyright (C) 2013 Atmel Corporation. All rights reserved.
 *
 * \asf_license_start
 *
 * \page License
 *
 * 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. The name of Atmel may not be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 4. This software may only be redistributed and used in connection with an
 *    Atmel microcontroller product.
 *
 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL 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.
 *
 * \asf_license_stop
 *
 */

/**
 * \page asfdoc_samd20_extint_callback_use_case Quick Start Guide for EXTINT - Callback
 *
 * In this use case, the EXTINT module is configured for:
 *  - External interrupt channel connected to the board LED is used
 *  - External interrupt channel is configured to detect both input signal edges
 *  - Callbacks are used to handle detections from the External Interrupt
 *
 * This use case configures a physical I/O pin of the device so that it is
 * routed to a logical External Interrupt Controller channel to detect rising
 * and falling edges of the incoming signal. A callback function is used to
 * handle detection events from the External Interrupt module asynchronously.
 *
 * When the board button is pressed, the board LED will light up. When the board
 * button is released, the LED will turn off.
 *
 * \section asfdoc_samd20_extint_callback_setup Setup
 *
 * \subsection asfdoc_samd20_extint_callback_setup_prereq Prerequisites
 * There are no special setup requirements for this use-case.
 *
 * \subsection asfdoc_samd20_extint_callback_setup_code Code
 * Copy-paste the following setup code to your user application:
 * \snippet qs_extint_callback.c setup
 *
 * Add to user application initialization (typically the start of \c main()):
 * \snippet qs_extint_callback.c setup_init
 *
 * \subsection asfdoc_samd20_extint_callback_setup_flow Workflow
 * -# Create an EXTINT module channel configuration struct, which can be filled
 *    out to adjust the configuration of a single external interrupt channel.
 *  \snippet qs_extint_callback.c setup_1
 * -# Initialize the channel configuration struct with the module's default
 *    values.
 *    \note This should always be performed before using the configuration
 *          struct to ensure that all values are initialized to known default
 *          settings.
 *
 *  \snippet qs_extint_callback.c setup_2
 * -# Adjust the configuration struct to configure the pin MUX (to route the
 *    desired physical pin to the logical channel) to the board button, and to
 *    configure the channel to detect both rising and falling edges.
 *  \snippet qs_extint_callback.c setup_3
 * -# Configure external interrupt channel with the desired channel settings.
 *  \snippet qs_extint_callback.c setup_4
 * -# Register a callback function \c extint_handler() to handle detections from
 *    the External Interrupt controller.
 *  \snippet qs_extint_callback.c setup_5
 * -# Enable the registered callback function for the configured External
 *    Interrupt channel, so that it will be called by the module when the
 *    channel detects an edge.
 *  \snippet qs_extint_callback.c setup_6
 * -# Define the EXTINT callback that will be fired when a detection event
 *    occurs. For this example, a LED will mirror the new button state on each
 *    detection edge.
 *  \snippet qs_extint_callback.c setup_7
 *
 *
 * \section asfdoc_samd20_extint_callback_main Use Case
 *
 * \subsection asfdoc_samd20_extint_callback_main_code Code
 * Copy-paste the following code to your user application:
 * \snippet qs_extint_callback.c main
 *
 * \subsection asfdoc_samd20_extint_callback_main_flow Workflow
 * -# External interrupt events from the driver are detected asynchronously; no
 *    special application \c main() code is required.
 */
