Pico W Pinout and Wiring Guide

🔌 Raspberry Pi Pico W Pinout Guide - Complete Reference

🔌 What You'll Learn:

📊 Understand all 40 pins on the Pico W
🔧 Know which pins are for GPIO, ADC, PWM, I2C, SPI, UART
⚡ Learn power pin limitations (3.3V = 300mA max)
⚠️ Avoid common wiring mistakes (3.3V logic only!)

📊 Important Pin Functions

GP0, GP1: UART0 - Serial communication (TX/RX)
GP2, GP3: I2C1 (SDA/SCL) - I2C sensors (BME280, etc.)
GP4, GP5: SPI0 - SPI devices, displays
GP6-GP9: PWM - Servo control, LED dimming
GP10-GP13: SPI1 - SD cards, additional SPI sensors
GP14-GP15: PWM - Motor control, LEDs, buzzers
GP26-GP28: ADC pins - Analog sensors (soil moisture, light, pH) - ONLY these 3!
GP22: Onboard LED (built-in LED control)
GP23, GP24, GP25: Used by WiFi - avoid using these

💡 ADC Pins are LIMITED!

Only GP26, GP27, GP28 can read analog signals (0-3.3V → 0-65535). All other GPIO are digital only (0 or 1). For multiple analog sensors, use these 3 pins or add an external ADC.

🔌 Power Pins

3.3V (pin 36): Output for sensors (max 300mA total)
5V (pin 40): Input from USB or external 5V power supply
VSYS (pin 39): 1.8-5.5V input for battery operation
GND: Multiple ground pins available (pins 3, 8, 13, 18, 23, 28, 33, 38)
RUN (pin 36): Reset pin - pull low to reset

⚠️ CRITICAL WARNINGS:

3.3V LOGIC ONLY: Pico W uses 3.3V - NEVER connect 5V to GPIO pins!

ADC pins are GP26, GP27, GP28 ONLY (pins 31, 32, 34)

GP23, GP24, GP25 are used by WiFi - avoid using them

3.3V pin max current: 300mA total (sensors + onboard)

VSYS range: 1.8-5.5V (can use single 18650 battery directly!)

🔌 Common Sensor Wiring Examples

Soil Moisture Sensor (Analog)

Pico W → Soil Moisture Sensor 3.3V (pin 36) → VCC GND (pin 38) → GND GP26 (pin 31) → AO (Analog Output)

DHT22 (Digital)

Pico W → DHT22 3.3V (pin 36) → VCC GND (pin 38) → GND GP0 (pin 1) → DATA (with 10kΩ pull-up to 3.3V)

Relay Module (Digital Output)

Pico W → Relay Module 3.3V (pin 36) → VCC GND (pin 38) → GND GP1 (pin 2) → IN (Control pin)

I2C Sensor (BME280)

Pico W → BME280 3.3V (pin 36) → VCC GND (pin 38) → GND GP2 (pin 4) → SDA GP3 (pin 5) → SCL

💡 Quick Reference - Best Pins For:

Analog sensors (soil, light, pH): GP26, GP27, GP28 (ONLY these!)

I2C Devices (BME280, OLED): GP2 (SDA), GP3 (SCL)

UART/Serial (GPS, debugging): GP0 (TX), GP1 (RX)

Simple buttons/LEDs: Any free GPIO except GP23-25

Relays/Pumps: Any free GPIO (use external 5V power)

🎯 Key Takeaways:

✅ 40 total pins: 26 GPIO, 3 ADC, 8 GND, power pins

✅ ADC pins: GP26, GP27, GP28 only (pins 31, 32, 34)

✅ 3.3V output max 300mA - enough for 2-3 sensors

✅ VSYS (pin 39) accepts 1.8-5.5V - perfect for 18650 battery

✅ Avoid GP23, GP24, GP25 (reserved for WiFi)

💡 Key Takeaways:

Apply these concepts directly to your farm or project.

Take notes on important details for the quiz.

Use the button below to track your progress.

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