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Blink (Built-in LED)

Blink the built-in LED on the ESP32-S3 WROOM. This is the "Hello World" of microcontroller programming.

New Concepts

  • Thonny
  • Python
  • ESP32 Microcontroller
  • Breadboard

Component List

Components

No external circuit required — this project is powered over USB and uses the LED built into the ESP32-S3 WROOM board (connected internally to GPIO2).

WROOM Board

Code

File: 01_first_examples/code/Blink.py

from time import sleep_ms
from machine import Pin

led = Pin(2, Pin.OUT)  # create LED object from pin2, Set Pin2 to output

while True:
    led.value(1)    # Turn LED On
    sleep_ms(1000)
    led.value(0)    # Turn LED Off
    sleep_ms(1000)

How to Run

Online (while connected to PC)

  1. Open Thonny and navigate to 01_first_examples/code/.
  2. Double-click Blink.py to open it.
  3. Click Stop/Restart backend and wait for the connection to be confirmed.
  4. Click Run current script — the LED starts blinking.

If you disconnect the USB cable or press Reset, the code stops. Use offline mode to persist it.

Code Explanation

In plain language the code:

  • Import the functions sleep_ms and Pin used in this project
  • Setup GPIO Pin 2 as output and assign it to the led variable
  • Loop forever
    • Turn LED On
    • Sleep for 1 second
    • Turn LED Off
    • Sleep for 1 second
# -- Setup --

# Import the functions `sleep_ms` and `Pin` used in this project
from time import sleep_ms
from machine import Pin

# Setup GPIO Pin 2 as output and assign it to the led variable
led = Pin(2, Pin.OUT)

# -- Program Loop --

# Loop forever
while True:
    led.value(1)    # Turn LED On
    sleep_ms(1000)  # Sleep for 1 second
    led.value(0)    # Turn LED Off
    sleep_ms(1000)  # Sleep for 1 second

DEFINITION - GPIO stands for General Purpose Input Output. So this pin can either send out a signal, as in this case, or read in a signal, for example to read a button press.

Key Concepts

  • Pin(id, mode) — creates a GPIO object. Pin.OUT sets it as an output.
  • led.value(0/1) — sets the pin LOW (0) or HIGH (1).
  • sleep_ms(ms) — pauses execution for the given number of milliseconds.
  • while True — infinite loop; runs forever until interrupted.
  • Python uses indentation (not braces) to define code blocks.

Further Exploration

Try the following:

  • Make the LED flash very fast
    • Can you make it flash so fast it looks like it is on all the time?
  • Make the LED on time different than the off time.

Back to Module

Adapted from Python_Tutorial.pdf Project 1.1