ESP32 Timer Interrupt ISR Causes Crash

In this tutorial, you'll learn about ESP32 Timer Interrupt ISR Causes Crash. We cover key concepts, practical examples, and best practices.

The Problem

ESP32 timer ISR crashes the system due to long operations or missing IRAM attributes.

Quick Fix

Wrong

void onTimer(void* arg) {
  Serial.println("Tick");  // Serial not safe in ISR!
}

Guru Meditation Error. Core panic. CPU halted.

Right

volatile bool timerFired = false;
void IRAM_ATTR onTimer(void* arg) {
  timerFired = true;
  timer_group_clr_intr_status_in_isr(TIMER_GROUP_0, TIMER_0);
  timer_ll_set_raw_counter_value(TIMER_GROUP_0, TIMER_0, 0);
}
void loop() {
  if (timerFired) {
    timerFired = false;
    Serial.println("Tick");  // Safe outside ISR
  }
}

Tick
Tick
Tick
(ISR fires every second without crashing)

Prevention

Declare ISR with IRAM_ATTR. Clear interrupt flag in ISR. Keep ISR minimal (set flag only). Handle data in main loop. Do NOT call Serial, delay, malloc, or WiFi in ISR.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ