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+/*

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

+ * @brief   Generic GPT Driver.

+ * @details This module implements a generic timer driver. The timer can be

+ *          programmed in order to trigger callbacks after a specified time

+ *          period or continuously with a specified interval.

+ * @pre     In order to use the GPT driver the @p HAL_USE_GPT option

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

+ *

+ * @section gpt_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];

+

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

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

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

+    continuous [label="GPT_CONT..S\nContinuous\nMode"];

+    oneshot [label="GPT_ONESHOT\nOne Shot\nMode"];

+

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

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

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

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

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

+    ready -> continuous [label="\ngptStartContinuous()"];

+    continuous -> ready [label="\ngptStopTimer()"];

+    continuous -> continuous [label=">callback<"];

+    ready -> oneshot [label="\ngptStartOneShot()\ngptPolledDelay()"];

+    oneshot -> ready [label="\n>callback<\nor\nDelay Over"];

+  }

+ * @enddot

+ *

+ * @section gpt_2 GPT Operations.

+ * This driver abstracts a generic timer composed of:

+ * - A clock prescaler.

+ * - A main up counter.

+ * - A comparator register that resets the main counter to zero when the limit

+ *   is reached. A callback is invoked when this happens.

+ * .

+ * The timer can operate in three different modes:

+ * - <b>Continuous Mode</b>, a periodic callback is invoked until the driver

+ *   is explicitly stopped.

+ * - <b>One Shot Mode</b>, a callback is invoked after the programmed period

+ *   and then the timer automatically stops.

+ * - <b>Delay Mode</b>, the timer is used for inserting a brief delay into

+ *   the execution flow, no callback is invoked in this mode.

+ * .

+ * @ingroup IO

+ */