ptScheduler - Library Documentation

ptScheduler is a non-preemptive task scheduler for Arduino supported microcontrollers that helps you to write non-blocking periodic tasks easily without using an RTOS.

This is the documentation for ptScheduler version 1.1.2. If you are using a different version, choose the version from left pane.

Pretty tiny Scheduler or ptScheduler is a non-preemptive task scheduler library for Arduino that helps you to write non-blocking, periodic tasks easily and effectively without using ordinary delay routines or using millis() function on your own.

Under the hood, ptScheduler uses the native millis() implementation of Arduino. The millis() function is a hardware timer based ISR that increments a global counter variable (unsigned integer) every millisecond.

When you create a new ptScheduler object, you can specify the time intervals and execution modes. All the class member variables and functions are public and therefore gives you full control over your tasks, allowing dynamically changing the behavior of the task.

To run a task, just enclose the call() function inside any conditional statements, either inside your infinite loop or inside a function. Every time you invoke the call() function, it checks if the elapsed time is larger than the preset interval. If yes, it will return true and cause the code under the conditional block to be executed once.

ptScheduler is good mainly for control applications that require periodic polling of sensors, GPIOs and other IO devices. ptScheduler tasks can coexist with preemptive tasks such as FreeRTOS tasks.

ptScheduler is an open source library developed by Vishnu Mohanan.

Visit GitHub page

Basic Usage

Here's a Hello World example. sayHello is a ptScheduler task initialized with 1000 millisecond time period. The corresponding call() function for sayHello is enclosed inside an if statement. The clause will be executed every 1 second, printing "Hello World" to the serial monitor. You can change this time period dynamically, or get the number of times the clause was executed.

#include "ptScheduler.h"

//create tasks
ptScheduler sayHello = ptScheduler(1000);

//setup function runs once
void setup() {
  Serial.begin(9600);
}

//infinite loop
void loop() {
  if (sayHello.call()) {  //executed every second
    Serial.println("Hello World");
  }

  //add other tasks and non-blocking code here
}

Here is a blink example. The blinkLed task is set to run every 500 milliseconds. The associated if clause will toggle the LED state every 500 milliseconds. Notice that the new task does interfere with timing of the sayHello task. Both tasks run only at their specific periods. On line 23 is a statement that will be executed continuously.

#include "ptScheduler.h"

//create tasks
ptScheduler sayHello = ptScheduler(1000);
ptScheduler blinkLed = ptScheduler(500);

//setup function runs once
void setup() {
  Serial.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
}

//infinite loop
void loop() {
  if (sayHello.call()) {  //executed every second
    Serial.println("Hello World");
  }
  
  if (blinkLED.call()) {
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));  //toggle LED
  }
  
  Serial.println(analogRead(A0));  //continuous task
}

Tutorial

A complete tutorial on ptScheduler is available at CIRCUITSTATE.