GPIO Setup & First Script

GPIO Pinout Overview

Every Raspberry Pi (since the Pi 2/Zero era) has a 40-pin GPIO header. Run this from an SSH session to print a labeled diagram for your specific board:

pinout

(part of the gpiozero package — already installed on Raspberry Pi OS). Key things to know:

• Pins are 3.3V logic, not 5V — see Safety Notes below.
• Physical pin numbers (1–40) differ from BCM GPIO numbers (e.g. physical pin 11 is GPIO17) — most Python libraries, including gpiozero, use BCM numbers.
• Dedicated 5V and 3.3V power pins and GND pins are broken out alongside the GPIO pins — check the pinout diagram before wiring anything.

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Enabling I2C / SPI

GPIO digital pins work with no extra setup. If your project uses an I2C or SPI sensor/display, enable the relevant interface first:

sudo raspi-config

Go to Interface Options, then enable I2C and/or SPI as needed. Reboot afterward.

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Installing gpiozero

gpiozero is the standard, beginner-friendly Python library for GPIO on Raspberry Pi OS — it's preinstalled on both the Desktop and Lite images. Confirm it's available:

python3 -c "import gpiozero; print(gpiozero.__version__)"

If it's missing (e.g. a minimal custom image), install it with:

sudo apt install python3-gpiozero

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Your First Script: Blink an LED

Wire an LED (with a current-limiting resistor, e.g. 330Ω) between GPIO17 (physical pin 11) and a GND pin, then create blink.py:

from gpiozero import LED
from time import sleep

led = LED(17)  # BCM GPIO17

while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)

Run it:

python3 blink.py

Press Ctrl+C to stop. The LED should turn on and off once per second.

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Safety Notes

• 3.3V logic only — Raspberry Pi GPIO pins are not 5V tolerant. Connecting a 5V signal directly to a GPIO pin can permanently damage the board. Use a logic-level shifter when working with 5V sensors/modules.
• Current limits — each GPIO pin can safely source/sink a limited current (a few mA per pin, tens of mA total across all pins combined, depending on the board). Never connect a motor, relay coil, or high-current LED directly to a GPIO pin — drive it through a transistor, MOSFET, or relay module instead.

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What's Next?

• Try JustFlash if you're also working with an Arduino/ESP32/ESP8266/Pico alongside your Pi
• Explore Basic Electronics fundamentals like resistors, LEDs, and breadboards

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