/*
    ChibiOS - Copyright (C) 2006..2018 Giovanni Di Sirio

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

/**
 * @defgroup SERIAL_USB Serial over USB Driver
 * @brief   Serial over USB Driver.
 * @details This module implements an USB Communication Device Class
 *          (CDC) as a normal serial communication port accessible from
 *          the device application.
 * @pre     In order to use the USB over Serial driver the
 *          @p HAL_USE_SERIAL_USB option must be enabled in @p halconf.h.
 *
 * @section usb_serial_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).
 * @dot
  digraph example {
    rankdir="LR";
    node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true",
          width="0.9", height="0.9"];
    edge [fontname=Helvetica, fontsize=8];

    uninit [label="SDU_UNINIT", style="bold"];
    stop [label="SDU_STOP\nLow Power"];
    ready [label="SDU_READY\nClock Enabled"];

    uninit -> stop [label=" sduInit()"];
    stop -> stop [label="\nsduStop()"];
    stop -> ready [label="\nsduStart()"];
    ready -> stop [label="\nsduStop()"];
    ready -> ready [label="\nsduStart()"];
    ready -> ready [label="\nAny I/O operation"];
  }
 * @enddot
 *
 * @ingroup HAL_COMPLEX_DRIVERS
 */
