core/systick/systick.c

   1 /**************************************************************************/
   2 /*!
   3     @file     systick.c
   4     @author   K. Townsend (microBuilder.eu)
   5     @date     22 March 2010
   6     @version  0.10
   7
   8     @section DESCRIPTION
   9
  10     Controls the 24-bit 'system tick' clock, which can be used as a
  11     generic timer or to control time sharing with an embedded real-time
  12     operating system (such as FreeRTOS).
  13
  14     @section Example
  15
  16     @code
  17     #include "core/cpu/cpu.h"
  18     #include "core/systick/systick.h"
  19
  20     void main (void)
  21     {
  22       cpuInit();
  23
  24       // Start systick timer with one tick every 10ms
  25       systickInit(10);
  26
  27       while(1)
  28       {
  29       }
  30     }
  31     @endcode
  32
  33     @section LICENSE
  34
  35     Software License Agreement (BSD License)
  36
  37     Copyright (c) 2010, microBuilder SARL
  38     All rights reserved.
  39
  40     Redistribution and use in source and binary forms, with or without
  41     modification, are permitted provided that the following conditions are met:
  42     1. Redistributions of source code must retain the above copyright
  43     notice, this list of conditions and the following disclaimer.
  44     2. Redistributions in binary form must reproduce the above copyright
  45     notice, this list of conditions and the following disclaimer in the
  46     documentation and/or other materials provided with the distribution.
  47     3. Neither the name of the copyright holders nor the
  48     names of its contributors may be used to endorse or promote products
  49     derived from this software without specific prior written permission.
  50
  51     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  52     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  53     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  54     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  55     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  56     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  57     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  58     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  59     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  60     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  61 */
  62 /**************************************************************************/
  63
  64 #include "systick.h"
  65
  66 #ifdef CFG_SDCARD
  67 #include "drivers/fatfs/diskio.h"
  68 volatile uint32_t fatTicks = 0;
  69 #endif
  70
  71 volatile uint32_t systickTicks = 0;             // 1ms tick counter
  72 volatile uint32_t systickRollovers = 0;
  73
  74 /**************************************************************************/
  75 /*!
  76     @brief Systick interrupt handler
  77 */
  78 /**************************************************************************/
  79 void SysTick_Handler (void)
  80 {
  81   systickTicks++;
  82
  83   // Increment rollover counter
  84   if (systickTicks == 0xFFFFFFFF) systickRollovers++;
  85
  86   #ifdef CFG_SDCARD
  87   fatTicks++;
  88   if (fatTicks == 10)
  89   {
  90     fatTicks = 0;
  91     disk_timerproc();
  92   }
  93   #endif
  94 }
  95
  96 /**************************************************************************/
  97 /*!
  98     @brief      Configures the systick timer
  99
 100     @param[in]  ticks
 101                 The number of clock cycles between each tick of the
 102                 systick timer. for example, 'CFG_CPU_CCLK / 1000' =
 103                 1 millisecond.  This value must not exceed 0x00FFFFFF.
 104 */
 105 /**************************************************************************/
 106 static uint32_t systickConfig(uint32_t ticks)
 107 {
 108   // Check if 'ticks' is greater than maximum value
 109   if (ticks > SYSTICK_STRELOAD_MASK)
 110   {
 111     return (1);
 112   }
 113
 114   // Reset counter
 115   systickTicks = 0;
 116
 117   // Set reload register
 118   SYSTICK_STRELOAD  = (ticks & SYSTICK_STRELOAD_MASK) - 1;
 119
 120   // Load the systick counter value
 121   SYSTICK_STCURR = 0;
 122
 123   // Enable systick IRQ and timer
 124   SYSTICK_STCTRL = SYSTICK_STCTRL_CLKSOURCE |
 125                    SYSTICK_STCTRL_TICKINT |
 126                    SYSTICK_STCTRL_ENABLE;
 127
 128   return (0);
 129 }
 130
 131 /**************************************************************************/
 132 /*!
 133     @brief      Initialises the systick timer
 134
 135     @param[in]  delayMs
 136                 The number of milliseconds between each tick of the systick
 137                 timer.
 138
 139     @note       The shortest possible delay is 1 millisecond, which will
 140                 allow fine grained delays, but will cause more load on the
 141                 system than a 10mS delay.  The resolution of the systick
 142                 timer needs to be balanced with the amount of processing
 143                 time you can spare.  The delay should really only be set
 144                 to 1 mS if you genuinely have a need for 1mS delays,
 145                 otherwise a higher value like 5 or 10 mS is probably
 146                 more appropriate.
 147 */
 148 /**************************************************************************/
 149 void systickInit (uint32_t delayMs)
 150 {
 151   systickConfig ((CFG_CPU_CCLK / 1000) * delayMs);
 152 }
 153
 154 /**************************************************************************/
 155 /*!
 156     @brief      Causes a blocking delay for 'delayTicks' ticks on the
 157                 systick timer.  For example: systickDelay(100) would cause
 158                 a blocking delay for 100 ticks of the systick timer.
 159
 160     @param[in]  delayTicks
 161                 The number of systick ticks to cause a blocking delay for
 162
 163     @Note       This function takes into account the fact that the tick
 164                 counter may eventually roll over to 0 once it reaches
 165                 0xFFFFFFFF.
 166 */
 167 /**************************************************************************/
 168 void systickDelay (uint32_t delayTicks)
 169 {
 170   uint32_t curTicks;
 171   curTicks = systickTicks;
 172
 173   // Make sure delay is at least 1 tick in case of division, etc.
 174   if (delayTicks == 0) delayTicks = 1;
 175
 176   if (curTicks > 0xFFFFFFFF - delayTicks)
 177   {
 178     // Rollover will occur during delay
 179     while (systickTicks >= curTicks)
 180     {
 181       while (systickTicks < (delayTicks - (0xFFFFFFFF - curTicks)));
 182     }
 183   }
 184   else
 185   {
 186     while ((systickTicks - curTicks) < delayTicks);
 187   }
 188 }
 189
 190 /**************************************************************************/
 191 /*!
 192     @brief      Returns the current value of the systick timer counter.
 193                 This value is incremented by one every time an interrupt
 194                 fires for the systick timer.
 195 */
 196 /**************************************************************************/
 197 uint32_t systickGetTicks(void)
 198 {
 199   return systickTicks;
 200 }
 201
 202 /**************************************************************************/
 203 /*!
 204     @brief      Returns the current value of the systick timer rollover
 205                 counter. This value is incremented by one every time the
 206                 tick counter rolls over from 0xFFFFFFFF to 0.
 207 */
 208 /**************************************************************************/
 209 uint32_t systickGetRollovers(void)
 210 {
 211   return systickRollovers;
 212 }
 213
 214 /**************************************************************************/
 215 /*!
 216     @brief      Returns the approximate number of seconds that the
 217                 systick timer has been running.
 218 */
 219 /**************************************************************************/
 220 uint32_t systickGetSecondsActive(void)
 221 {
 222   uint32_t currentTick = systickTicks;
 223   uint32_t rollovers = systickRollovers;
 224   uint32_t secsActive = currentTick / (1000 / CFG_SYSTICK_DELAY_IN_MS);
 225   secsActive += rollovers * (0xFFFFFFFF / (1000 / CFG_SYSTICK_DELAY_IN_MS));
 226
 227   return secsActive;
 228 }
 229