pxt-calliope/docs/reference/js/lessons/blink/activity.md

blink activity

Turn an LED on and off with forever

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@video td/videos/blink-0

Let's learn how to blink an LED.

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Have you ever tried to blink a flashlight at night? The concept is fairly simply: turn on the light, wait for a little, turn off the light, wait again, and repeat. That's exactly what we need to code to get a blinking LED.

Let's start by adding a line of code that turns on the LED at position 2, 2.

led.plot(2, 2) 

Run your script to make sure it's correct. Then, let's add code to pause 500 milliseconds and turn off the LED.

led.plot(2, 2)
basic.pause(500) 
led.unplot(2, 2) 

We've got the LED blinking once. Let's add another pause and turn on the LED again.

led.plot(2, 2)
basic.pause(500)
led.unplot(2, 2)
basic.pause(500) 
led.plot(2, 2) 

The current code works but it only blinks once! We are going to use a basic->forever loop and move the code inside it to repeat it forever. We've dropped the second led-plot line since we don't need it in the loop.

basic.forever(() => {
    led.plot(2, 2)
    basic.pause(500)
    led.unplot(2, 2)
    basic.pause(500)
})

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Excellent, you're ready to continue with the challenges!

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