LaunchPad MSP430 pomodoro timer using Energia

I know a lot of people who bought the Texas Instruments MSP430 LaunchPad development kit but never really got into it. I’m one of them; the $4.30 purchase price was compelling, but the requirement to install a huge proprietary IDE (with its own embedded C dialect) was just too much.

For this reason, Energia is great. It’s a fork of the Wiring/Arduino development environment for the MSP430. Looks just like Arduino, but quite red:

The basics of the language are the same, although the pin names and functions are different from the Arduino. The basic board also has a red and a green LED, a user button, and the obligatory reset button.

Just to try out Energia, I wanted a useful project that only used the onboard hardware. I came up with a version of a pomodoro timer, similar to the one used in The Pomodoro Technique® time management method. The one I made has the following features:

  • 25 minute “green light” work period
  • 5 minute “red light” rest period
  • At the end of the rest period, the green and red lights flash. You can choose to restart the timer (with the reset button), or turn the lights off with the user button.
  • You can turn the timer off at any time with the user button, and restart it from zero with the reset button.

For me, this electronic version has several advantages over the wind-up official timer:

  • it doesn’t tick or ring distractingly
  • it’s cheaper than the real thing
  • it always resets to the same time.

It does have a couple of possible disadvantages, though:

  • it doesn’t give an indication of time left
  • it’s not very accurate, since it uses the MSP430’s internal oscillator. Mine seems to give an approximately 26 minute work period, with a rest time that’s proportionally longer.

Here’s the code (tested on a MSP-EXP430G2 board, version 1.4):


 launchpomodoro - simple task/rest timer for TMS430/Energia

 On reset: Green LED on for 25 minutes
 After 25 minutes: Red LED
 After 30 minutes: Flashing Red/Green LED (until reset)
 On button press: all lights off.

 scruss - 2012-10-15


// 25 minutes
#define ENDWORKTIME 1500000
// 30 minutes
#define ENDRESTTIME 1800000

unsigned long start=0;
int red=1; // for light flashing state at end of rest time
int green=0;

void setup() {
  pinMode(RED_LED, OUTPUT);
  pinMode(PUSH2, INPUT);
  digitalWrite(GREEN_LED, HIGH); // start work
  digitalWrite(RED_LED, LOW); // stop rest

void loop () {
  if ((millis()-start)>ENDWORKTIME) {
    digitalWrite(GREEN_LED, LOW); // stop work
    digitalWrite(RED_LED, HIGH); // start rest

  if ((millis()-start)>ENDRESTTIME) {
    flicker(); // warn that we've overrun

  if (digitalRead(PUSH2) == LOW) { // push quiet/off switch

void flicker() { // toggle LEDs and wait a bit
  digitalWrite(GREEN_LED, green);
  digitalWrite(RED_LED, red);

void off() { // appear to be off
  digitalWrite(GREEN_LED, LOW); // lights off
  digitalWrite(RED_LED, LOW);
  while (1) { // loop until reset

(or if you’d rather have the archived sketch:

It would be trivial to port this to Arduino, but you would need some external LEDs, resistors and a pushbutton.


  1. I’ve been using this a bit this week, and the timer runs almost exactly at 26 minutes at my office temperature. If you want it to be closer to 25/5 instead of 26/5.2, change the #define lines at the top to:

    #define ENDWORKTIME 1442308
    #define ENDRESTTIME 1730769

    Microcontroller clocks aren’t really designed for long duration timing, so even this might be a bit off. I’m going to keep using the original numbers. They keep the 5:1 work/rest ratio intact, and any more time spent fiddling with this kind of goes against good time management anyway.

  2. Thanks, Bernhard! I didn’t know about the new low-power sleep() function in Energia. I haven’t used it since 2012, long before this was added.

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