How can I run multiple separate loops independently from one another in Arduino IDE?

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Summary

Running multiple independent loops in Arduino is challenging due to the blocking nature of delay(). The provided code sequentially executes loops, causing LEDs to flash in sequence rather than concurrently. The root cause is the single-threaded execution model of Arduino, which halts all operations during delay().

Root Cause

  • Blocking delay(): The delay() function pauses the entire program, preventing concurrent execution.
  • Single-threaded execution: Arduino runs one task at a time, making true parallelism impossible without external libraries or hardware.

Why This Happens in Real Systems

  • Microcontroller limitations: Arduino Uno operates on a single core, executing instructions sequentially.
  • Lack of multitasking: Without an operating system, Arduino cannot context-switch between tasks.

Real-World Impact

  • Non-concurrent behavior: LEDs flash sequentially instead of independently.
  • Inefficient resource use: CPU remains idle during delay(), wasting processing power.

Example or Code

unsigned long previousBlueMillis = 0;
unsigned long previousGreenMillis = 0;
unsigned long previousRedMillis = 0;
const long blueInterval = 1000;
const long greenInterval = 500;
const long redInterval = 200;

void loop() {
  unsigned long currentMillis = millis();

  // Blue LED
  if (currentMillis - previousBlueMillis >= blueInterval) {
    previousBlueMillis = currentMillis;
    digitalWrite(bluLED, !digitalRead(bluLED));
  }

  // Green LED
  if (currentMillis - previousGreenMillis >= greenInterval) {
    previousGreenMillis = currentMillis;
    digitalWrite(grnLED, !digitalRead(grnLED));
  }

  // Red LED
  if (currentMillis - previousRedMillis >= redInterval) {
    previousRedMillis = currentMillis;
    digitalWrite(redLED, !digitalRead(redLED));
  }
}

How Senior Engineers Fix It

  • Replace delay() with millis(): Use non-blocking timing to check elapsed time without halting execution.
  • Leverage libraries: Use TaskScheduler or Ticker for pseudo-multitasking.
  • Optimize code: Minimize blocking operations and maximize efficiency.

Why Juniors Miss It

  • Overreliance on delay(): Beginners often use delay() without understanding its blocking nature.
  • Lack of timing alternatives: Unawareness of millis() for non-blocking timing.
  • Misunderstanding concurrency: Assuming Arduino supports true parallelism without external tools.

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