Wed May 06 2026
Got excited about a Raspberry Pi Pico starter kit. Started with LED blink, then added button control and learned about pull-up resistors.
Written by: Cesar
2 min read
All this Shelly business got me excited about playing with a Raspberry Pi Pico starter kit I purchased a while back.
I decided to fire up the old Thonny IDE and try the simple hello world example: blinking the on-board LED on GPIO25.
from machine import Pin
import utime
led_onboard = Pin(25, Pin.OUT)
while True:
led_onboard.value(1)
utime.sleep(1)
led_onboard.value(0)
utime.sleep(1)Works perfectly. LED blinks on, off, on, off. Dead simple.
Then I decided to connect a physical button and make it control the LED:
from machine import Pin
import time
led = Pin(25, Pin.OUT)
button = Pin(14, Pin.IN, Pin.PULL_UP)
while True:
if button.value() == 0:
print("Pressed!")
led.toggle()
else:
print("Released")
time.sleep(0.5)All was going pretty well. This also worked on the first try — button press toggles the LED.
Then I looked at what a pull-up resistor actually does. This is where things clicked.
Without a pull-up resistor: the pin floats. It has no definite voltage reading. Is it high? Is it low? Unstable. Unreliable.
With a pull-up resistor: the reading is stable. The pin reads as 1 (HIGH) by default. When you ground it (press the button), it reads as 0 (LOW). Clear signal. No noise.
That’s why the code uses Pin.PULL_UP — it tells the Pico to use the internal pull-up resistor so the button press is clean and reliable.
Then I started on another small project and that’s when things got interesting.
More to come.
Why this matters: From Shelly smart switches to Raspberry Pi Pico microcontrollers, the fundamentals are the same: GPIO pins, voltage logic, button debouncing, state management. Once you understand one, the others make sense fast.