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Library

Task Scheduler

Rating:

10

Author: Richard Lowe

Last Updated: 2016-02-25

Package Version: 1.1.0.5

Category: Timers (Real time clock)

Downloaded: 2915 times

Followed by: 6 users

License: MIT license  

This is a light Round Robin style task scheduler. You can define the maximum number of tasks and add those tasks to be ran at scheduled intervals. You will need to provide a clock source.

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Library Blog

Example of usage: 

Used STM32 Mini M4.  This example shows that with a 1 second timer and the scheduler blink the LED at the same rate.  

#include "scheduler.h"

#define ARM

sbit STAT at ODR13_GPIOC_ODR_bit;
sbit DATA at ODR12_GPIOC_ODR_bit;

void InitTimer()
{
#ifdef AVR
    // use 1/8 of system clock frequency
    TCCR0B |= (1<<CS01);
    // inital timer value = 0
    TCNT0 = 0x00;
    // enable Timer0 Overflow interrupt
    TIMSK0 |= (1<<TOIE0);
#endif
#ifdef ARM
    RCC_APB1ENR.TIM2EN = 1;
    TIM2_CR1.CEN = 0;
    TIM2_PSC = 1;
    TIM2_ARR = 60000;
    NVIC_IntEnable(IVT_INT_TIM2);
    TIM2_DIER.UIE = 1;
    TIM2_CR1.CEN = 1;
#endif
}

#ifdef ARM
void initCaliTimer()
{
    RCC_APB1ENR.TIM3EN = 1;
    TIM3_CR1.CEN = 0;
    TIM3_PSC = 1874;
    TIM3_ARR = 64000;
    NVIC_IntEnable(IVT_INT_TIM3);
    TIM3_DIER.UIE = 1;
    TIM3_CR1.CEN = 1;

}
#endif

void task1()
{
    UART_Write_Text("1 Second has passed\n");
    STAT = ~STAT;                            // Toggle STAT LED

}

void task2()
{
    UART_Write_Text("5 Seconds has passed\n");

}

void main()
{
#ifdef AVR
    asm sei;
    UART1_Init(38400);
    UART_Write_Text("System Startup\n");
#endif
    schedulerInit();
    addTask(0, task1, SECONDS_1);
    addTask(1, task2, SECONDS_5);
    InitTimer();
#ifdef ARM
    initCaliTimer();
    // configure DATA and STAT pins as output
    GPIO_Digital_Output(&GPIOC_BASE, _GPIO_PINMASK_12 | _GPIO_PINMASK_13);
    STAT = 0;                                  // turn OFF the STAT LED
    DATA = 1;                                  // turn OFF the DATA LED
    UART1_Init(115200);
    Delay_ms(10);
    EnableInterrupts();
    UART1_Write_Text("System Startup\n");
#endif

    while(1) {
        dispatchTasks();
    }
}

#ifdef AVR
void Timer0Overflow_ISR() iv IVT_ADDR_TIMER0_OVF ics ICS_AUTO {
    schedulerClock();
}
#endif
#ifdef ARM
void Timer2_interrupt() iv IVT_INT_TIM2 {
    TIM2_SR.UIF = 0;
    schedulerClock();
}

void Timer3_interrupt() iv IVT_INT_TIM3 {
    TIM3_SR.UIF = 0;
    DATA = ~DATA;                            // Toggle DATA LED
}

#endif

This version adds some flexibility in your clock source.  When initialized, use any clock from 10ms to 1000ms ( must be % 2 ), no 545 values.


Tasks can be run every 1 second up to 45 days.


Also added a stop and start.  Some weird behavior could have happened with very fast MCU's where the tasks started counting down before the dispatch was called.  This would have rolled the period over making it run 45 days from initialization.  When ready, call task_scheduler_start() and that issue is avoided.

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