Appendix B
Appendix B: Pinout guide
A complete reference to every GPIO pin's functions on the Pico 2
Raspberry Pi Pico, Pico W, Pico 2, and Pico 2 W expose 26 of their microcontroller’s GPIO (general-purpose input/output) pins by routing them straight out to header pins on the board. GP0 to GP22 are digital only and GP26–28 are able to be used either as digital GPIO or as ADC (analogue-to-digital converter) inputs, selectable in software. Most of the GPIO pins also offer secondary functionality for SPI, I2C, or UART communication protocols. All GPIO pins may also be used with PWM (pulse-width modulation) — see Chapter 8, Temperature gauge for more details.
- VBUS is the micro USB input voltage, connected to micro USB port pin 1. This is nominally 5V (0V if the USB is not connected or not powered).
- VSYS is the main system input voltage, which can vary in the allowed range 1.8V to 5.5V, and which is used by the on-board SMPS (switch mode power supply) to generate the 3.3V for the RP2040 or RP2350 and its GPIO.
- 3V3_EN connects to the on-board SMPS enable pin, and is pulled high (to VSYS) via a 100 kΩ resistor. To disable the 3.3V (which also de-powers the RP2040), short this pin low.
- 3V3 is the main 3.3V supply to RP2040 or RP2350 and its IO, generated by the on-board SMPS. This pin can be used to power external circuitry (the maximum output current will depend on the RP2040 or RP2350 load and VSYS voltage, but you must keep the load on this pin less than 300 mA).
- ADC_VREF is the ADC power supply (and reference) voltage, and is generated on Pico by filtering the 3.3V supply. This pin can be used with an external reference if better ADC performance is required.
- AGND is the ground reference for GPIO26–29; there is a separate analogue ground plane running under these signals and terminating at this pin. If the ADC is not used or ADC performance is not critical, this pin can be connected to digital ground.
- RUN is the RP2040 or RP2350 enable pin, and has an internal (on-chip) pull-up resistor to 3.3V of about ~50 kΩ. Short this pin low to reset.
