TaskSched

Overview

TaskSched is a cooperative multitasking scheduler for Arduino processors, designed as a simpler alternative to existing schedulers like TaskScheduler. It provides a flexible and efficient way to manage multiple tasks in Arduino projects, particularly tested on ESP32 and ESP8266 processors.

A cooperative task scheduler is a system that manages the execution of multiple tasks, but with a twist compared to a traditional scheduler. Here's the key difference:

Cooperative: In a cooperative scheme, tasks are responsible for voluntarily giving up control of the processor when they're done or need to wait for something. The scheduler simply provides a starting point and trusts the tasks to behave. This is in contrast to a preemptive scheduler, where the operating system can interrupt a running task and switch to another one.

Here's a breakdown of how cooperative scheduling works:

• The scheduler starts a task.
• The task runs until it finishes its work or needs to wait for something (like user input or data from another task).
• The task then signals the scheduler that it's done or needs to wait.
• The scheduler picks another task to run.

Pros and Cons:

• Pros: Simpler to implement, fewer system resources needed.
• Cons: Unpredictable behavior if tasks don't cooperate, can lead to unresponsive systems if a task gets stuck.

Use Cases:

• Often used in early operating systems or embedded systems with limited resources.
• Can be a good choice for specific situations where tasks have well-defined execution times and don't rely on external events heavily.
• Even with events that have an ideterminite delay such as waiting for a DHCP server to issue an IP, one task may start the connect and schedule another task to monitor for a response periodically.

Contents

• Main Features
• Installation
• Usage
  • Creating Tasks
  • Task Methods
  • Scheduler
• Examples
• API Reference
• Issues
• Contributing

Main Features

1. Periodic task execution: Tasks can be set to run at specified intervals, with times specified in milliseconds or seconds.
2. Task enable/disable support: Tasks can be dynamically enabled or disabled.
3. Iteration control: Tasks can be set to run for a specific number of iterations or indefinitely.
4. Immediate or delayed execution: Tasks can be scheduled to run immediately when enabled or wait for the interval to expire.
5. Task restart and parameter modification: Tasks can be restarted with original or new parameters (interval, callback function, etc.).
6. Flexible timing control: The scheduler can be run periodically in the main loop.

Installation

To install TaskSched, clone the repository:

git clone https://github.com/AverageGuy/tasksched.git

Or download the ZIP file.

Usage

Creating Tasks

Tasks are created using the Task constructor:

<Task *task =new Task(callback, interval, enabled, iterations, name, runImmediately);
Task *task = new Task(VoidCallBack, interval, enabled, iterations, name, runImmediately);

• TaskCallback: Function to be called (must accept a Task* parameter)
• VoidCallback: Function to be called (no parameter)
• interval: Time between calls milliseconds if integer
• enabled: Whether the task starts enabled
• iterations: Number of times to run (0 for infinite)
• name: Descriptive name for the task
• runImmediately: Whether to run immediately when enabled without waiting for interval to expire

Task Methods

Key methods for managing tasks: (https://averageguy.github.io/task-docs/classTask.html)

• enable(): Enable the task
• disable(): Disable the task
• restart(): Restart the task with original parameters
• setInterval(newInterval): Set a new interval
• setIterations(newIterations): Set a new iteration count
• isEnabled(): Check if the task is enabled
• isFirstIteration(): Check if it's the first iteration
• isLastIteration(): Check if it's the last iteration

Scheduler

The Sched class manages multiple tasks:

Task *task=new Task(runTest, 500, true, 6, "First", true);
Sched scheduler;
scheduler.addTask(task);
scheduler.begin();

void loop() {
    scheduler.run();
}

Key methods in the Sched class (https://averageguy.github.io/task-docs/classSched.html)

• enable(): Enable the scheduler
• disable(): Disable the scheduler
• begin(): Initialize the scheduler
• run(): Loop throught the tasks and run them one at a time, if they are scheduled.
• getSize(): Return the number of tasks in the run queue
• displayStatus(): Returns a String with info about some or all of the tasks in the queue.
• addTask(): Adds a task to the queue.
• isEnabled(): Returns a true if the scheduler is enabled or false if it is not.
• getTasks(): Returns a list of the tasks. See the example/SkedBlink2.ino file for examples of ways to use this list.

Examples

See the examples directory for basic examples of blinking an LED using TaskSched and others. Also look at the wiki. It has more examples and explanations.

API Reference

For detailed API documentation, please refer to the Doxygen-generated documentation https://averageguy.github.io/task-docs/

Issues

If you encounter any issues or have feature requests, please open an issue on the GitHub repository.

Contributing

Contributions to TaskSched are welcome. Please feel free to submit pull requests or open issues to discuss potential improvements.