lwcs is as Lightweight Cooperative Scheduler for short.

Pros

• lightweight
• platform independent
• easy to use
• no dynamic memory allocation

Cons

• non-preemtive
• non Real-Time
• easy to break up things

lwcs is a portable, platform independent non-preemtive multitasking process sheduler. Cooperative means that no context switching is used, but instead, each process must voluntary yield control one to another and work in cooperation with each other. Process workflow is controlled by shceduler busy loop. This feature gives the biggest problem of cooperative sheduler - each process should not be blocking and do not use busy waiting on it own, state-machines could be used instead, if action on different events is required inside the process.

Usage example

Simply put lwcs.h and lwcs.c files in your working directory.

!!! Make sure every task is simple fast and non-blocking.

#include <led.h>
#include "lwcs.h"

static const uint32_t jiffiesInMilliSec = 1;
extern lwcs_Time getJiffies(void);

static const lwcs_Time BLINK_RED_LED_PERIOD = 500;
static const lwcs_Time BLINK_GREEN_LED_PERIOD = 900;

int blinkLedForever(void);
int blinkLedOnce(void);

void main(void) {
    lwcs_initialize(jiffiesInMilliSec, &getJiffies);

    lwcs_addTask(&blinkRedLedForever, BLINK_RED_LED_PERIOD);
    lwcs_addTask(&blinkGreenLedOnce, BLINK_GREEN_LED_PERIOD);

    lwcs_run();
}

int blinkLedForever() {
    LED_invert(LED_RED);

    // if task returns 0 then task is preserved in scheduler run list
    return 0;
}

int blinkLedOnce() {
    LED_invert(LED_GREEN);

    // if task returns -1 then task is removed from scheduler run list
    return -1;
}