Your Pico talks to hardware through a series of pins along both its edges. Most of these pins work as a General-Purpose Input/Output (GPIO) pin, meaning they can be programmed to act as either an input or an output and have no fixed purpose of their own. Some pins have extra features and alternative modes for communicating with more complicated hardware; others have a fixed purpose.

• GPIO Pins – These can be programmed to send or receive signals. They're used to turn things on or off or detect if a button has been pressed.
• Power Pins – Provide constant 3.3V or 5V power to components like sensors or displays.
• Ground (GND) Pins – Complete the circuit by connecting your components to the Pi's ground. The Raspberry Pi Pico's ground pins are 3, 8, 13, 18, 23, 28, 33, 38.

Types of Pins

3V3 - A source of 3.3V power, the same voltage your Pico runs at internally, generated from the VSYS input. This power supply can be switched on and off using the 3V3_EN pin above it, which also switches your Pico off.

VSYS (~2.5V) - A pin directly connected to your Pico’s internal power supply, which cannot be switched off without also switching Pico off.

VBUS - A source of 5V power taken from your Pico’s micro USB port, and used to power hardware which needs more than 3.3 V.

ADC - A GPIO pin which ends in ‘ADC’ and a number can be used as an analogue input as well as a digital input or output – but not both at the same time.

ADC_VREF - A special input pin which sets a reference voltage for any analogue inputs.

AGND - A special ground connection for use with the ADC_VREF pin.

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A reference guide to pinouts can be accessed directly in the Raspberry Pi OS. Open the command terminal and type pinout, then press enter.