digitalWrite HIGH และ LOW

Your pin is set to OUTPUT, but it is still silent. To actually switch it on or off, you use one new command: digitalWrite. ✨

A digital pin lives in just two states. It is either fully on, called HIGH, or fully off, called LOW. There is nothing in between.

Writing HIGH pushes the pin up to roughly 5 volts. That voltage flows through your LED and lights it. HIGH is the on signal.

Writing LOW drops the pin back to 0 volts. With no voltage to push current, the LED goes dark. LOW is the off signal.

digitalWrite needs two things: which pin to change, and the state to set. So you pass a pin and then either HIGH or LOW.

You set a pin's mode once, but you can change its state any time. Put digitalWrite in loop() to switch the LED on demand.

To blink, you simply alternate. Drive the pin HIGH, then drive it LOW, and the LED toggles between glowing and dark.

Run HIGH then LOW with nothing between and the LED flickers far too fast for your eyes. You need a pause, which comes next lesson.

HIGH and LOW are just friendly names. Under the hood they equal 1 and 0, so digitalWrite(pin, 1) does the same as HIGH.

digitalWrite changes a pin but never reports it. To check what an output pin is doing, you track the state yourself in a variable.

The onboard LED needs no parts, but an external one can pull too much current. Always protect it with a resistor, covered soon.

Your LED is connected and the pin is OUTPUT. How do you turn it off?

You now control a pin with digitalWrite, using HIGH for on and LOW for off. Next you will add timing so the blink is actually visible. 🎉