220 lines
7.2 KiB
C
220 lines
7.2 KiB
C
/**************************************************************************/
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/*!
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@file systick.c
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@author K. Townsend (microBuilder.eu)
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@date 22 March 2010
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@version 0.10
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@section DESCRIPTION
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Controls the 24-bit 'system tick' clock, which can be used as a
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generic timer or to control time sharing with an embedded real-time
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operating system (such as FreeRTOS).
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@section Example
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@code
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#include "core/cpu/cpu.h"
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#include "core/systick/systick.h"
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void main (void)
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{
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cpuInit();
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// Start systick timer with one tick every 10ms
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systickInit(10);
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while(1)
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{
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}
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}
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@endcode
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@section LICENSE
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Software License Agreement (BSD License)
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Copyright (c) 2010, microBuilder SARL
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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3. Neither the name of the copyright holders nor the
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names of its contributors may be used to endorse or promote products
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derived from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
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DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**************************************************************************/
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#include "systick.h"
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volatile uint32_t systickTicks = 0; // 1ms tick counter
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volatile uint32_t systickRollovers = 0;
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void tick_wrapper(void);
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/**************************************************************************/
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/*!
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@brief Systick interrupt handler
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*/
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/**************************************************************************/
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void SysTick_Handler (void)
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{
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systickTicks++;
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// Increment rollover counter
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if (systickTicks == 0xFFFFFFFF) systickRollovers++;
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tick_wrapper();
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}
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/**************************************************************************/
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/*!
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@brief Configures the systick timer
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@param[in] ticks
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The number of clock cycles between each tick of the
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systick timer. for example, 'CFG_CPU_CCLK / 1000' =
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1 millisecond. This value must not exceed 0x00FFFFFF.
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*/
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/**************************************************************************/
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static uint32_t systickConfig(uint32_t ticks)
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{
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// Check if 'ticks' is greater than maximum value
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if (ticks > SYSTICK_STRELOAD_MASK)
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{
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return (1);
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}
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// Reset counter
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systickTicks = 0;
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// Set reload register
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SYSTICK_STRELOAD = (ticks & SYSTICK_STRELOAD_MASK) - 1;
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// Load the systick counter value
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SYSTICK_STCURR = 0;
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// Enable systick IRQ and timer
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SYSTICK_STCTRL = SYSTICK_STCTRL_CLKSOURCE |
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SYSTICK_STCTRL_TICKINT |
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SYSTICK_STCTRL_ENABLE;
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return (0);
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}
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/**************************************************************************/
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/*!
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@brief Initialises the systick timer
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@param[in] delayMs
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The number of milliseconds between each tick of the systick
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timer.
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@note The shortest possible delay is 1 millisecond, which will
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allow fine grained delays, but will cause more load on the
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system than a 10mS delay. The resolution of the systick
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timer needs to be balanced with the amount of processing
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time you can spare. The delay should really only be set
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to 1 mS if you genuinely have a need for 1mS delays,
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otherwise a higher value like 5 or 10 mS is probably
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more appropriate.
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*/
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/**************************************************************************/
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void systickInit (uint32_t delayMs)
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{
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systickConfig ((CFG_CPU_CCLK / 1000) * delayMs);
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}
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/**************************************************************************/
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/*!
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@brief Causes a blocking delay for 'delayTicks' ticks on the
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systick timer. For example: systickDelay(100) would cause
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a blocking delay for 100 ticks of the systick timer.
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@param[in] delayTicks
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The number of systick ticks to cause a blocking delay for
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@Note This function takes into account the fact that the tick
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counter may eventually roll over to 0 once it reaches
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0xFFFFFFFF.
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*/
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/**************************************************************************/
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void systickDelay (uint32_t delayTicks)
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{
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uint32_t curTicks;
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curTicks = systickTicks;
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// Make sure delay is at least 1 tick in case of division, etc.
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if (delayTicks == 0) delayTicks = 1;
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if (curTicks > 0xFFFFFFFF - delayTicks)
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{
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// Rollover will occur during delay
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while (systickTicks >= curTicks)
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{
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while (systickTicks < (delayTicks - (0xFFFFFFFF - curTicks)));
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}
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}
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else
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{
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while ((systickTicks - curTicks) < delayTicks);
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}
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}
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/**************************************************************************/
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/*!
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@brief Returns the current value of the systick timer counter.
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This value is incremented by one every time an interrupt
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fires for the systick timer.
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*/
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/**************************************************************************/
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uint32_t systickGetTicks(void)
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{
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return systickTicks;
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}
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/**************************************************************************/
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/*!
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@brief Returns the current value of the systick timer rollover
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counter. This value is incremented by one every time the
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tick counter rolls over from 0xFFFFFFFF to 0.
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*/
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/**************************************************************************/
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uint32_t systickGetRollovers(void)
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{
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return systickRollovers;
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}
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/**************************************************************************/
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/*!
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@brief Returns the approximate number of seconds that the
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systick timer has been running.
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*/
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/**************************************************************************/
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uint32_t systickGetSecondsActive(void)
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{
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uint32_t currentTick = systickTicks;
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uint32_t rollovers = systickRollovers;
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uint32_t secsActive = currentTick / (1000 / CFG_SYSTICK_DELAY_IN_MS);
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secsActive += rollovers * (0xFFFFFFFF / (1000 / CFG_SYSTICK_DELAY_IN_MS));
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return secsActive;
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}
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