I´m using LowPower.h and PinChangeInt.h libraries to put my Arduino into the sleep mode every 8 seconds and then it wakes up, modifies a counter and it goes to sleep again, but also I need to wake it up when a button is pressed asynchronously.

I´ve reached to wake up the Arduino every 8 seconds using LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF) and, in other code, I´ve also reached to wake it up while it sleeps indefinitely with LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF) but I can´t combine that periodical awakening with the asynchronous awakening.

Here is my code:

void setup(){


    //Pines declaration

    loopsToSend = setTimeToSend();  //

    //The three async buttons 
    PCintPort::attachInterrupt(4, readOpinion,RISING);
    PCintPort::attachInterrupt(5, readOpinion,RISING);
    PCintPort::attachInterrupt(6, readOpinion,RISING);

void loop(){

    if(loops < loopsToSend ){

        byte opinionValue = readOpinion(); //This method must awake the Arduino ASYNC to give a value to the opinionValue var, write the result in the file and go to sleep 

        if(opinionValue != 0){
            Serial.println("Button pressed!");

            //Writing result in a file
        //Go to sleep 8 seconds
        LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
        opinionValue = 0;
    else {

        if(opiniones > 0){
            //Send file using GSM module
            loops = 0;

Can anyone help me? Thanks

  • Only the INT0 (pin2) and INT1 (pin3) pins can wake the arduino from SLEEP_MODE_PWR_DOWN. So I don't know how the buttons could have worked in the first place. Are you sure the uC was really sleeping?
    – Gerben
    Commented Nov 25, 2016 at 14:39
  • But I´m using the PinChangeInt.h to use any pin to generate the interrupt and it works.
    – cpinamtz
    Commented Nov 25, 2016 at 14:44
  • @Gerben According to Nick Gammons How do interrupts work on the Arduino Uno and similar boards? refference Q/A and the comments bellow, it woks (I've tested it). The External Interrupts in all modes and PinChange interrupts too.
    – KIIV
    Commented Nov 25, 2016 at 18:15
  • This is an exact duplicate of arduino.stackexchange.com/q/31659/17196
    – Ghanima
    Commented Apr 29, 2017 at 12:38

1 Answer 1


This one works for me:

#include <PinChangeInterrupt.h>
#include <LowPower.h>

// I want to know when it was interrupted by PCINT:
volatile byte flag = 0;
void handler() {
    flag = 1;

void setup() {
  pinMode(A0, INPUT_PULLUP);
  attachPCINT(digitalPinToPCINT(A0), handler, CHANGE);

void loop() {
  Serial.println("entering powerDown sleep mode");
  Serial.flush(); // wait for sending all data 

  LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);

  if (flag == 1) {
    flag = 0;
    Serial.println("Pin change interrupt");
  } else {

However if you use RISING (or FALLING), it also wakes up from the sleep when pin changes back to the oposite state (and it'll be reported as Timeout).

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