Arduino library to use timer 2 with a configurable resolution. Based on MsTimer2 by Javier Valencia. It's called FlexiTimer2 because it's based on MsTimer2, but offers more flexibility, since it has a configurable timer resolution.

It works on:

• ATmega1280 (thanks to Manuel Negri).
• ATmega328 (thanks Jerome Despatis).
• ATmega48/88/168 and ATmega128/8.
• Atmega2560
• Teensy

Originally written by Wim Leers for the project associated with the "Mobile & Pervasive Computing" course at Hasselt University in Belgium.

Methods

FlexiTimer2::set(unsigned long units, double resolution, void (*f)())

this function sets a time on units time the resolution for the overflow. Each overflow, "f" will be called. "f" has to be declared void with no parameters. E.g. units=1, resolution = 1.0/3000 will call f 3000 times per second, whereas it would be called only 1500 times per second when units=2.

FlexiTimer2::set(unsigned long ms, void (*f)())

this function sets a time on ms (1/1000th of a second) for the overflow. Each overflow, "f" will be called. "f" has to be declared void with no parameters. Shorthand for calling the function above with resolution = 0.001.

FlexiTimer2::start()

enables the interrupt.

FlexiTimer2::stop()

disables the interrupt.

Source code

Code hosted on GitHub

License: LGPL (like MsTimer2)

Download:

• FlexiTimer2.zip
• FlexiTimer2.tgz

A fork is available here:

• a new version is available here

After downloading the zip file, rename the zip file something simple like "FlexiTimer2.zip". (The Arduino IDE sometimes chokes on zip files with dashes or other symbols in the file name).

Install it like any other Arduino library. (See http://arduino.cc/en/Guide/Libraries ). It should end up in the {arduino-path}/hardware/libraries/ folder.

Example (MsTimer2 compatibility)

This example is *identical* to the one for MsTimer2, but "Ms" has been replaced with "Flexi". Really, that's all you have to do to port your code, if you want to be prepared for more granular control, but don't need it yet.

// Toggle LED on pin 13 each second
#include <FlexiTimer2.h>

void flash() {
  static boolean output = HIGH;

  digitalWrite(13, output);
  output = !output;
}

void setup() {
  pinMode(13, OUTPUT);

  FlexiTimer2::set(500, flash); // 500ms period
  FlexiTimer2::start();
}

void loop() {
}

Important note

The line

FlexiTimer2::set(500, flash);

is equivalent with

FlexiTimer2::set(500, 1.0/1000, flash);

The latter configures a resolution of 1/1000th of a second, i.e.: 1 millisecond.

Example

In this example, we show how to use FlexiTimer2 to achieve sub-millisecond resolution for your interrupts.

The original author of FlexiTimer2 needed to simulate PWM over a 8x8 multiplexed grid of LEDs. Without going into detail on that, he needed 2880 interrupts per second to update the LEDs to be able to generate a decent range of colors.

#include <FlexiTimer2.h>

void simulatePWM() {
    // Add your code to simulate PWM here.
}

void setup() {
  FlexiTimer2::set(1, 1.0/2880, simulatePWM);
  FlexiTimer2::start();
}

void loop() {
}

Note that the PWM signals created by Timer 2 will become unusable while Flexitimer2 is using Timer 2.

On Arduino Uno, those are pins 3 and 11.

On Arduino Mega, those are pins 9 and 10.

Bugs

Report bugs in the issue queue.