Raspberry Pi 4 Pinout

Overview

The Raspberry Pi 4 is a full single-board computer, not a microcontroller: it boots Linux from an SD card or USB drive, rather than running a single compiled program. Its 40-pin GPIO header still works a lot like the boards elsewhere in these guides, 3.3V logic, I2C, SPI, UART and PWM are all here, just controlled from Python (or any language) running on top of a full OS instead of bare-metal firmware.

Getting started

Unlike the microcontroller boards in these guides, there’s no sketch to compile and upload, you flash an operating system image to an SD card once, then the Pi boots into it like a regular computer.

Hello World: blink an LED

The microcontroller equivalent of “Hello World”: GPIO17 toggles once a second. Wire an LED (with a resistor) to GPIO17 (physical pin 11), then run this directly on the Pi, no separate upload step needed.

from gpiozero import LED
from time import sleep

led = LED(17)  # GPIO17, physical pin 11
while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)

Run with: python3 blink.py. gpiozero ships preinstalled on Raspberry Pi OS.

Specifications

Official specifications for the Raspberry Pi 4 Model B.

Pinout diagram

The full 40-pin GPIO header.

GPIO quick reference

Physical pin numbers count around the header, BCM numbers are what Python libraries expect by default, the two don’t match.

Serial console (UART)

Useful for debugging headless boots, or talking to another serial device directly. Enable it in raspi-config first, it’s off by default.

Safety notes