Electron sleep causes stack overflow

Firmware
1

Why does my simple sleep test program give a stack overflow error (13 red flashes)? I’m trying to debug my electron not waking from sleeping.

#include "Particle.h"
#define AC_MONITOR_PIN D2

long sleepTime = 2;
Timer c(5000, runTimer);
int i = 0;

void setup() {
    Serial.begin(9600);
    c.start();
    pinMode(AC_MONITOR_PIN, INPUT_PULLDOWN);
    Serial.printf("starting, %d\n", millis());
    runTimer();
}

void loop() {
}

void runTimer() {
    Serial.printf("Tic %d %d\n", i, millis());
    i++;
    if (i > 2) {
        System.sleep(AC_MONITOR_PIN, RISING, sleepTime);
        Serial.println("wakeup");
    }
}
2

Software Timers run on their own thread which has only got a limited stack quota.
Just as an ISR needs to be kept small and fast, Software Timer callback should too.

A viable way out of this is to let the timer only set a flag and leave the “heavy lifting” to loop() which regularly checks the flag.

2 Likes
3

It doesn’t look like this is a stack quota issue. Instead the sleep process takes about 6 seconds to complete. During that time, the timer function continues to run. So when I put the “sleep” command in the timer function it gets called twice and looks like that may be causing the issue.

I fixed this by moving the sleep function out of the timer and setting a “sleepOnlyOnce” flag.

1 Like