/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
                 2011 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @defgroup EXT EXT Driver
 * @brief   Generic EXT Driver.
 * @details This module implements a generic EXT (EXTernal) driver.
 * @pre     In order to use the EXT driver the @p HAL_USE_EXT option
 *          must be enabled in @p halconf.h.
 *
 * @section ext_1 Driver State Machine
 * The driver implements a state machine internally, not all the driver
 * functionalities can be used in any moment, any transition not explicitly
 * shown in the following diagram has to be considered an error and shall
 * be captured by an assertion (if enabled).
 * @if LATEX_PDF
 * @dot
  digraph example {
    size="5, 7";
    rankdir="LR";

    node [shape=circle, fontname=Sans, fontsize=8, fixedsize="true", width="0.9", height="0.9"];
    edge [fontname=Sans, fontsize=8];

    uninit [label="EXT_UNINIT", style="bold"];
    stop  [label="EXT_STOP\nLow Power"];
    active [label="EXT_ACTIVE"];

    uninit -> stop [label="extInit()"];
    stop -> stop [label="\nextStop()"];
    stop -> active [label="\nextStart()"];
    active -> stop [label="\nextStop()"];
    active -> active [label="\nextStart()"];
  }
 * @enddot
 * @else
 * @dot
  digraph example {
    rankdir="LR";

    node [shape=circle, fontname=Sans, fontsize=8, fixedsize="true", width="0.9", height="0.9"];
    edge [fontname=Sans, fontsize=8];

    uninit [label="EXT_UNINIT", style="bold"];
    stop  [label="EXT_STOP\nLow Power"];
    active [label="EXT_ACTIVE"];

    uninit -> stop [label="extInit()"];
    stop -> stop [label="\nextStop()"];
    stop -> active [label="\nextStart()"];
    active -> stop [label="\nextStop()"];
    active -> active [label="\nextStart()"];
  }
 * @enddot
 * @endif
 *
 * @section ext_2 EXT Operations.
 * This driver abstracts generic external interrupt sources, a callback
 * is invoked when a programmable transition is detected on one of the
 * configured channels. Several channel modes are possible.
 * - <b>EXT_CH_MODE_DISABLED</b>, channel not used.
 * - <b>EXT_CH_MODE_RISING_EDGE</b>, callback on a rising edge.
 * - <b>EXT_CH_MODE_FALLING_EDGE</b>, callback on a falling edge.
 * - <b>EXT_CH_MODE_BOTH_EDGES</b>, callback on a both edges.
 * .
 * @ingroup IO
 */