ทำไฟกะพริบโดยไม่ใช้ delay ด้วย millis

The millis function returns how many milliseconds your board has been running since it powered on. It is a free, always-counting stopwatch. ⏱️

Store millis in an unsigned long. The count grows huge over time, and a plain int would overflow in under a minute.

Instead of pausing, you remember the last time you acted, then keep checking how much time has passed since then on every loop.

Keep a variable like previousMillis to store when you last toggled the LED. You will compare it against the current time each pass.

Choose an interval, say 1000 milliseconds, as the gap between blinks. Acting only after this much time passes gives a steady rhythm.

Each loop, subtract previousMillis from the current millis. If the gap is at least your interval, it is time to act.

The instant you act, set previousMillis to the current time. This restarts the countdown so the next blink waits a full interval again.

Inside the timed block you simply toggle the LED, flipping it on if it was off and off if it was on, for a clean blink.

Between blinks the loop keeps spinning at full speed, free to read sensors or buttons. Nothing is ever frozen waiting.

After about 49 days millis wraps to zero, but the subtraction trick still gives the right gap, so your timing keeps working.

This millis pattern works for any repeating task, not just blinking. Change the interval and the action and you can schedule anything.

Why do we store the result of millis in an unsigned long?

You learned the millis pattern: remember the last time, check the elapsed gap, then act and reset. Now your board blinks while staying fully alert. 🎉