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+/*

+    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,

+                 2011,2012,2013 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/>.

+

+                                      ---

+

+    A special exception to the GPL can be applied should you wish to distribute

+    a combined work that includes ChibiOS/RT, without being obliged to provide

+    the source code for any proprietary components. See the file exception.txt

+    for full details of how and when the exception can be applied.

+*/

+

+/**

+ * @defgroup USB USB Driver

+ * @brief   Generic USB Driver.

+ * @details This module implements a generic USB (Universal Serial Bus) driver

+ *          supporting device-mode operations.

+ * @pre     In order to use the USB driver the @p HAL_USE_USB option

+ *          must be enabled in @p halconf.h.

+ *

+ * @section usb_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=Helvetica, fontsize=8, fixedsize="true",

+          width="0.9", height="0.9"];

+    edge [fontname=Helvetica, fontsize=8];

+

+    stop  [label="USB_STOP\nLow Power"];

+    uninit [label="USB_UNINIT", style="bold"];

+    ready [label="USB_READY\nClock Enabled"];

+    selected [label="\nUSB_SELECTED\naddress\nassigned"];

+    active [label="\nUSB_ACTIVE\nconfiguration\nselected"];

+

+    uninit -> stop [label=" usbInit()", constraint=false];

+    stop -> stop [label="\nusbStop()"];

+    stop -> ready [label="\nusbStart()"];

+    ready -> stop [label="\nusbStop()"];

+    ready -> ready [label="\n\nusbStart()"];

+    ready -> ready [label="\nSUSPEND/WAKEUP\n>event_cb<"];

+    ready -> selected [label="\nSET_ADDRESS\n>event_cb<"];

+    selected -> stop [label="\nusbStop()"];

+    selected -> ready [label="\nUSB RESET\n>event_cb<"];

+    selected -> selected [label="\nSUSPEND/WAKEUP\n>event_cb<\n\nValid EP0 Message\n>requests_hook_cb<\n\nGET DESCRIPTOR\n>get_descriptor_cb<"];

+    selected -> active [label="\nSET_CONF(n)\n>event_cb<"];

+    active -> stop [label="\nusbStop()"];

+    active -> selected [label="\nSET_CONF(0)\n>event_cb<"];

+    active -> active [label="\nSUSPEND/WAKEUP\n>event_cb<\n\nValid EP0 Message\n>requests_hook_cb<\n\nGET DESCRIPTOR\n>get_descriptor_cb<\n\nEndpoints Activity\n >in_cb< or >out_cb<"];

+    active -> ready [label="\nUSB RESET\n>event_cb<"];

+  }

+ * @enddot

+ * @else

+ * @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];

+

+    stop  [label="USB_STOP\nLow Power"];

+    uninit [label="USB_UNINIT", style="bold"];

+    ready [label="USB_READY\nClock Enabled"];

+    selected [label="\nUSB_SELECTED\naddress\nassigned"];

+    active [label="\nUSB_ACTIVE\nconfiguration\nselected"];

+

+    uninit -> stop [label=" usbInit()", constraint=false];

+    stop -> stop [label="\nusbStop()"];

+    stop -> ready [label="\nusbStart()"];

+    ready -> stop [label="\nusbStop()"];

+    ready -> ready [label="\n\nusbStart()"];

+    ready -> ready [label="\nSUSPEND/WAKEUP\n>event_cb<"];

+    ready -> selected [label="\nSET_ADDRESS\n>event_cb<"];

+    selected -> stop [label="\nusbStop()"];

+    selected -> ready [label="\nUSB RESET\n>event_cb<"];

+    selected -> selected [label="\nSUSPEND/WAKEUP\n>event_cb<\n\nValid EP0 Message\n>requests_hook_cb<\n\nGET DESCRIPTOR\n>get_descriptor_cb<"];

+    selected -> active [label="\nSET_CONF(n)\n>event_cb<"];

+    active -> stop [label="\nusbStop()"];

+    active -> selected [label="\nSET_CONF(0)\n>event_cb<"];

+    active -> active [label="\nSUSPEND/WAKEUP\n>event_cb<\n\nValid EP0 Message\n>requests_hook_cb<\n\nGET DESCRIPTOR\n>get_descriptor_cb<\n\nEndpoints Activity\n >in_cb< or >out_cb<"];

+    active -> ready [label="\nUSB RESET\n>event_cb<"];

+  }

+ * @enddot

+ * @endif

+ *

+ * @section usb_2 USB Operations

+ * The USB driver is quite complex and USB is complex in itself, it is

+ * recommended to study the USB specification before trying to use the

+ * driver.

+ *

+ * @subsection usb_2_1 USB Implementation

+ * The USB driver abstracts the inner details of the underlying USB hardware.

+ * The driver works asynchronously and communicates with the application

+ * using callbacks. The application is responsible of the descriptors and

+ * strings required by the USB device class to be implemented and of the

+ * handling of the specific messages sent over the endpoint zero. Standard

+ * messages are handled internally to the driver. The application can use

+ * hooks in order to handle custom messages or override the handling of the

+ * default handling of standard messages.

+ *

+ * @subsection usb_2_2 USB Endpoints

+ * USB endpoints are the objects that the application uses to exchange

+ * data with the host. There are two kind of endpoints:

+ * - <b>IN</b> endpoints are used by the application to transmit data to

+ *   the host.<br>

+ * - <b>OUT</b> endpoints are used by the application to receive data from

+ *   the host.

+ * .

+ * The driver invokes a callback after finishing an IN or OUT transaction.

+ * States diagram for OUT endpoints in transaction mode:

+ * @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];

+

+    disabled [label="EP_DISABLED\nDisabled", style="bold"];

+    receiving [label="EP_BUSY\nReceiving"];

+    idle [label="EP_IDLE\nReady"];

+

+    disabled -> idle [label="\nusbInitEndpointI()"];

+    idle -> receiving [label="\nusbPrepareReceive()\nusbStartReceiveI()"];

+    receiving -> receiving [label="\nmore packets"];

+    receiving -> idle [label="\nreception end\n>out_cb<"];

+    receiving -> disabled [label="\nUSB RESET\nusbDisableEndpointsI()"];

+    idle -> disabled [label="\nUSB RESET\nusbDisableEndpointsI()"];

+  }

+ * @enddot

+ * <br><br>

+ * States diagram for IN endpoints in transaction mode:

+ * @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];

+

+    disabled [label="EP_DISABLED\nDisabled", style="bold"];

+    transmitting [label="EP_BUSY\nTransmitting"];

+    idle [label="EP_IDLE\nReady"];

+

+    disabled -> idle [label="\usbInitEndpointI()"];

+    idle -> transmitting [label="\nusbPrepareTransmit()\nusbStartTransmitI()"];

+    transmitting -> transmitting [label="\nmore packets"];

+    transmitting -> idle [label="\ntransmission end\n>in_cb<"];

+    transmitting -> disabled [label="\nUSB RESET\nusbDisableEndpointsI()"];

+    idle -> disabled [label="\nUSB RESET\nusbDisableEndpointsI()"];

+  }

+ * @enddot

+ * <br><br>

+ *

+ * @subsection usb_2_4 USB Callbacks

+ * The USB driver uses callbacks in order to interact with the application.

+ * There are several kinds of callbacks to be handled:

+ * - Driver events callback. As example errors, suspend event, reset event

+ *   etc.

+ * - Messages Hook callback. This hook allows the application to implement

+ *   handling of custom messages or to override the default handling of

+ *   standard messages on endpoint zero.

+ * - Descriptor Requested callback. When the driver endpoint zero handler

+ *   receives a GET DESCRIPTOR message and needs to send a descriptor to

+ *   the host it queries the application using this callback.

+ * - Start of Frame callback. This callback is invoked each time a SOF

+ *   packet is received.

+ * - Endpoint callbacks. Each endpoint informs the application about I/O

+ *   conditions using those callbacks.

+ * .

+ *

+ * @ingroup IO

+ */