arduino-timer - library for delaying function calls

THIS VERSION IS A FORK OF https://github.com/contrem/arduino-timer AND ADDS A FUNCTION TO CANCEL A TASK.

Simple non-blocking timer library for calling functions **in / at / every / cancel ** specified units of time. Supports millis, micros, time rollover, and compile time configurable number of tasks.

Use It

Include the library and create a Timer instance.

#include <timer.h>

auto timer = timer_create_default();

Or using the Timer constructors for different task limits / time resolution

Timer<10> timer; // 10 concurrent tasks, using millis as resolution
Timer<10, micros> timer; // 10 concurrent tasks, using micros as resolution

Call timer.tick() in the loop function

void loop() {
    timer.tick();
}

Make a function to call when the Timer expires

bool function_to_call(void *argument /* optional argument given to in/at/every */) {
    return true; // to repeat the action - false to stop
}

Call function_to_call in delay units of time (unit of time defaults to milliseconds).

timer.in(delay, function_to_call);
timer.in(delay, function_to_call, argument); // or with an optional argument for function_to_call

Call function_to_call at a specific time.

timer.at(time, function_to_call);
timer.at(time, function_to_call, argument); // with argument

Call function_to_call every interval units of time.

timer.every(interval, function_to_call);
timer.every(interval, function_to_call, argument); // with argument

Be fancy with lambdas

timer.in(1000, [](void*) -> bool { return false; });
timer.in(1000, [](void *argument) -> bool { return argument; }, argument);

API

/* Constructors */
/* Create a timer object with default settings - millis resolution, TIMER_MAX_TASKS (=16) task slots */
Timer<> timer_create_default(); // auto timer = timer_create_default();

/* Create a timer with max_tasks slots and time_func resolution */
Timer<size_t max_tasks = TIMER_MAX_TASKS, unsigned long (*time_func)(void) = millis> timer;
Timer<> timer; // Equivalent to: auto timer = timer_create_default()
Timer<10> timer; // Timer with 10 task slots
Timer<10, micros> timer; // timer with 10 task slots and microsecond resolution

/* Signature for handler functions */
bool handler(void *argument);

/* Timer Methods */
/* Ticks the timer forward - call this function in loop() */
void tick();

/* Calls handler with opaque as argument in delay units of time */
unsigned long  in(unsigned long delay, handler_t handler, void *opaque = NULL);

/* Calls handler with opaque as argument at time */
unsigned long  at(unsigned long time, handler_t handler, void *opaque = NULL);

/* Calls handler with opaque as argument every interval units of time */
unsigned long  every(unsigned long interval, handler_t handler, void *opaque = NULL);

/* Cancel a task before it gets executed */
bool cancel(unsigned long task_id);

NOTE: at, in, every return a task_id

Installation

Check out the instructions from Arduino.

OR copy src/timer.h into your project folder (you won't get managed updates this way).

Examples

Found in the examples/ folder.

The simplest example, blinking an LED every second (from examples/blink):

#include <timer.h>

auto timer = timer_create_default(); // create a timer with default settings

bool toggle_led(void *) {
  digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN)); // toggle the LED
  return true; // keep timer active? true
}

void setup() {
  pinMode(LED_BUILTIN, OUTPUT); // set LED pin to OUTPUT

  // call the toggle_led function every 1000 millis (1 second)
  timer.every(1000, toggle_led);
}

void loop() {
  timer.tick(); // tick the timer
}

LICENSE

Check the LICENSE file - 3-Clause BSD License

Notes

Currently only a software timer. Any blocking code delaying timer.tick() will prevent the timer from moving forward and calling any functions.

The library does not do any dynamic memory allocation.

The number of concurrent tasks is a compile time constant, meaning there is a limit to the number of concurrent tasks. The in / at / every functions return id 0 if the Timer is full.

Change the number of concurrent tasks using the Timer constructors. Save memory by reducing the number, increase memory use by having more. The default is TIMER_MAX_TASKS which is currently 16.