core/wdt/wdt.c

   1 /**************************************************************************/
   2 /*!
   3     @file     wdt.c
   4     @author   K. Townsend (microBuilder.eu)
   5     @date     22 March 2010
   6     @version  0.10
   7
   8     @section DESCRIPTION
   9
  10     Sets up the watchdog timer (WDT).  The WDT allows you to monitor
  11     whether the device is still executing properly.  If the watchdog
  12     isn't 'fed' within a pre-determined delay, it will raise an interrupt
  13     allowing you to decide if you want to reset the device, etc.
  14
  15     @code
  16     #include "core/cpu/cpu.h"
  17     #include "core/wdt/wdt.h"
  18     ...
  19     cpuInit();
  20
  21     // Initialise wdt with no reset on timeout
  22     wdtInit(false);
  23
  24     // Pat the watchdog (to start the timer)
  25     wdtFeed();
  26
  27     while (1)
  28     {
  29       // Keep the watchdog happy by regularly feeding it
  30       wdtFeed();
  31     }
  32     @endcode
  33
  34     @section LICENSE
  35
  36     Software License Agreement (BSD License)
  37
  38     Copyright (c) 2010, microBuilder SARL
  39     All rights reserved.
  40
  41     Redistribution and use in source and binary forms, with or without
  42     modification, are permitted provided that the following conditions are met:
  43     1. Redistributions of source code must retain the above copyright
  44     notice, this list of conditions and the following disclaimer.
  45     2. Redistributions in binary form must reproduce the above copyright
  46     notice, this list of conditions and the following disclaimer in the
  47     documentation and/or other materials provided with the distribution.
  48     3. Neither the name of the copyright holders nor the
  49     names of its contributors may be used to endorse or promote products
  50     derived from this software without specific prior written permission.
  51
  52     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  53     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  54     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  55     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  56     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  57     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  58     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  59     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  60     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  61     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  62 */
  63 /**************************************************************************/
  64
  65 #include "wdt.h"
  66
  67 #define WDT_FEED_VALUE          (0x003FFFFF)
  68
  69 volatile uint32_t wdt_counter;
  70
  71 /**************************************************************************/
  72 /*!
  73     IRQ Handler when the watchdog times out.  Any actions that you wish
  74     to take when a timeout occurs should be called from here.
  75 */
  76 /**************************************************************************/
  77 void WDT_IRQHandler(void)
  78 {
  79   /* Clear the time-out interrupt flag */
  80   WDT_WDMOD &= ~WDT_WDMOD_WDTOF;
  81   wdt_counter++;
  82 }
  83
  84 /**************************************************************************/
  85 /*!
  86     Setup the clock for the watchdog timer.  The default setting is 250kHz.
  87 */
  88 /**************************************************************************/
  89 static void wdtClockSetup (void)
  90 {
  91   /* Watchdog Configuration */
  92   /* Freq. = 0.5MHz, div = 2: WDT_OSC = 250kHz  */
  93   SCB_WDTOSCCTRL = SCB_WDTOSCCTRL_FREQSEL_0_5MHZ |
  94                    SCB_WDTOSCCTRL_DIVSEL_DIV2;
  95
  96   /* Set clock source (use WDT oscillator) */
  97   SCB_WDTCLKSEL = SCB_WDTCLKSEL_SOURCE_WATCHDOGOSC;
  98   SCB_WDTCLKUEN = SCB_WDTCLKUEN_UPDATE;
  99   SCB_WDTCLKUEN = SCB_WDTCLKUEN_DISABLE;
 100   SCB_WDTCLKUEN = SCB_WDTCLKUEN_UPDATE;
 101
 102   /* Wait until updated */
 103   while (!(SCB_WDTCLKUEN & SCB_WDTCLKUEN_UPDATE));
 104
 105   /* Set divider */
 106   SCB_WDTCLKDIV = SCB_WDTCLKDIV_DIV1;
 107
 108   /* Enable WDT clock */
 109   SCB_PDRUNCFG &= ~(SCB_PDRUNCFG_WDTOSC);
 110 }
 111
 112 /**************************************************************************/
 113 /*!
 114     Initialises the watchdog timer and sets up the interrupt.
 115 */
 116 /**************************************************************************/
 117 void wdtInit (bool reset)
 118 {
 119   /* Setup the WDT clock */
 120   wdtClockSetup();
 121
 122   /* Enable AHB clock to the WDT domain. */
 123   SCB_SYSAHBCLKCTRL |= SCB_SYSAHBCLKCTRL_WDT;
 124
 125   wdt_counter = 0;
 126
 127   /* Enable the WDT interrupt */
 128   NVIC_EnableIRQ(WDT_IRQn);
 129
 130   /* Set timeout value (must be at least 0x000000FF) */
 131   WDT_WDTC = WDT_FEED_VALUE;
 132
 133   /* Enable the watchdog timer (without system reset) */
 134   WDT_WDMOD = WDT_WDMOD_WDEN_ENABLED |
 135               reset ? WDT_WDMOD_WDRESET_ENABLED : WDT_WDMOD_WDRESET_DISABLED ;
 136 }
 137
 138 /**************************************************************************/
 139 /*!
 140     Feeds the watchdog to keep it from timing out.  Interrupts will be
 141     disabled while feeding the watchdog.
 142 */
 143 /**************************************************************************/
 144 void wdtFeed (void)
 145 {
 146   /* Pet the watchdog */
 147   __disable_irq();
 148   WDT_WDFEED = WDT_WDFEED_FEED1;
 149   WDT_WDFEED = WDT_WDFEED_FEED2;
 150   __enable_irq();
 151 }
 152