The XIAO RP2350 is Seeed's take on the Raspberry Pi Pico 2's chip, shrunk into the same 21 x 17.8mm form factor as the rest of the XIAO line. It's the most GPIO-generous board in the XIAO family by a wide margin -- 19 exposed GPIOs, against the 11 that every ESP32-based XIAO board offers -- because the RP2350 simply has more pins to spare and no radio silicon competing for header space.
Like the plain Raspberry Pi Pico 2, there's no wireless on this board at all -- no WiFi, no Bluetooth. What it does carry over from the RP2350 is the chip's unusual dual-architecture design: switchable between dual Arm Cortex-M33 cores and dual Hazard3 RISC-V cores in software, plus hardware security features like TrustZone and secure boot that neither the original RP2040 nor any ESP32-based XIAO board has.
This guide covers the board's full pin layout, its 19 usable GPIOs, the ADC and PWM behavior inherited directly from the RP2350, and the practical differences that set it apart from every other board in the XIAO lineup.
GPIO Pins and Numbering
Nineteen usable GPIOs on the header -- the most of any board in the XIAO line, and enough headroom that pin-budget pressure, the constant concern on the 11-pin ESP32-based XIAO boards, mostly disappears here.
// Arduino-style
pinMode(D0, OUTPUT);
digitalWrite(D0, HIGH);
# MicroPython
from machine import Pin
led = Pin(0, Pin.OUT)
led.value(1)
UART Over USB
Worth flagging since it trips people coming from other RP2350 boards: the XIAO RP2350's USB connection is a pure software USB stack running on the chip itself -- it doesn't use any GPIO pin. The board's physical UART pins are separate, wired to D6 (TX) and D7 (RX) on the front header, and function as a genuine hardware UART peripheral independent of the USB connection.
Dual-Architecture Boot Selection
The same RP2350 feature covered on the plain Pico 2 -- switching between Arm Cortex-M33 and Hazard3 RISC-V cores -- carries over here unchanged, and doesn't affect GPIO numbering or pin function at all either way.
ADC and PWM
The RP2350's ADC carries over with the same 12-bit resolution as the Pico 2, spread across several of the board's GPIOs -- fewer analog channels than the 19 total digital-capable pins, since ADC capability is still fixed in silicon to a specific subset.
from machine import ADC
sensor = ADC(0) # example ADC-capable pin — check your board's diagram
reading = sensor.read_u16()
PWM follows the same slice-based architecture as any RP2350 board -- GPIOs are grouped into slices sharing a base frequency, with independent duty cycles per channel within a slice. Nearly every GPIO supports PWM output; the practical constraint is avoiding slice conflicts when a project assigns several simultaneous PWM signals.
from machine import Pin, PWM
servo = PWM(Pin(1))
servo.freq(50)
servo.duty_u16(4000)
I2C, SPI, and Serial
The board exposes the RP2350's standard I2C0/I2C1 and SPI0/SPI1 peripherals across its 19 GPIOs, following the same flexible pin-to-peripheral mapping every RP2350 board shares -- any compatible pin pair can be assigned to a given bus in software rather than being hardwired to one fixed location.
from machine import I2C, Pin
i2c = I2C(0, sda=Pin(4), scl=Pin(5))
In the Arduino environment specifically, "Serial" on this board actually covers three distinct interfaces once the native USB stack is factored in alongside the physical UART -- worth knowing before assuming Serial and Serial1 map the way they do on a simpler board.
Hardware Security and Dual Architecture
The same RP2350 features covered on the plain Pico 2 carry over here unchanged: TrustZone-based secure/non-secure partitioning, signed boot support, and the ability to switch between Arm Cortex-M33 and Hazard3 RISC-V cores at boot. On a board this compact, aimed partly at production use in space-constrained designs, the security features are arguably more relevant here than on a purely hobbyist full-size Pico 2.
How the XIAO RP2350 Compares
| Board | Chip | Usable GPIO | Wireless | Battery charging | Best for |
|---|---|---|---|---|---|
| XIAO ESP32C3 | ESP32-C3 | 11 | WiFi 4, BLE 5.0 | Yes | Compact WiFi/BLE sensor projects |
| XIAO ESP32C6 | ESP32-C6 | 11 | WiFi 6, BLE 5.3, 802.15.4 | Yes | Compact Matter/Thread projects |
| XIAO RP2350 | RP2350 | 19 | None | Yes | GPIO-heavy compact projects, no wireless needed |
| Raspberry Pi Pico 2 | RP2350 | 26 | None | No | Same chip, more GPIO, larger board |
The XIAO RP2350 sits in a genuinely different niche than its ESP32-based XIAO siblings -- it's the pick when a project is space-constrained and GPIO-hungry and has no wireless requirement at all, a combination the ESP32-based XIAO boards can't cover given their 11-pin limit.
Power Pins
| Pin | Function | Notes |
|---|---|---|
| 5V | Power input | Via USB-C |
| 3V3 | Regulated 3.3V output/input | Powers onboard logic and small peripherals |
| GND | Ground |
Like the rest of the XIAO line, an integrated battery management system is built in, letting a LiPo cell connect directly via a JST pad with onboard charge management -- useful given how many 19-GPIO projects on a board this size end up being genuinely portable builds.
Practical Pin Usage Tips
Take advantage of the larger pin budget compared to the ESP32-based XIAO boards. With 19 GPIOs instead of 11, there's real room to give separate peripherals their own dedicated buses instead of sharing pins out of necessity.
Remember the UART pins are separate hardware from USB. Unlike boards where the Serial Monitor and a physical UART share the same underlying peripheral, this board's D6/D7 UART is genuinely independent of the USB connection.
Confirm firmware targets the RP2350, not the RP2040. Same gotcha as the plain Pico 2 -- existing RP2040 code generally ports over, but needs rebuilding against the correct chip target.
Default to the Arm Cortex-M33 cores unless there's a specific reason to switch. Same as the Pico 2 -- library and tooling support for the Hazard3 RISC-V option is comparatively immature.
Consider this board specifically when a project needs both compact size and real GPIO count. If a design would otherwise be forced onto an 11-pin ESP32-based XIAO board purely for the small footprint, but doesn't actually need wireless, this board removes that compromise entirely.
Summary: XIAO RP2350 Pin Reference at a Glance
Seeed XIAO RP2350 · 21 x 17.8mm · RP2350, dual Arm Cortex-M33 (or Hazard3 RISC-V) · 19 usable GPIO · Hardware UART on D6/D7 · No wireless radio · Onboard LiPo charging · TrustZone security
Which Projects the XIAO RP2350 Actually Fits
A strong fit: a compact project that genuinely needs more than 11 GPIOs -- a small robotics controller juggling several motor drivers and sensors, a compact synthesizer or audio project using several PIO-driven outputs at once, or any build where a full-size Pico 2 simply wouldn't fit the enclosure.
A weaker fit: anything needing wireless connectivity (there's no path to add it on this specific board without an external module eating into the pin budget), or simple projects with modest GPIO needs where an ESP32-based XIAO board's built-in WiFi/BLE would add more value than this board's extra pin count.
PIO on a Compact Board
The RP2350's Programmable I/O subsystem -- three independent PIO blocks capable of running small custom hardware-timed programs alongside the main CPU cores -- carries over to this board fully intact despite the smaller footprint. That matters more here than it might seem: PIO is what lets a project drive WS2812 LED strips, implement a custom serial protocol, or generate precise waveforms without burning CPU cycles on tight timing loops, and having the chip's full PIO capability available on a board this size is a genuine advantage for compact projects that would otherwise need a separate timing-critical peripheral chip just to keep the main footprint small.
Quick Answers to Common XIAO RP2350 Pin Questions
How does this compare to the ESP32-based XIAO boards? Far more GPIO (19 versus 11), but no wireless radio at all -- a genuinely different trade-off, not a strict upgrade or downgrade.
Is this the same chip as the Raspberry Pi Pico 2? Yes, the same RP2350, just in the smaller XIAO form factor with fewer exposed pins than the Pico 2's 26.
Does the USB connection use a GPIO pin? No -- it's a pure software USB stack on the chip itself, separate from the physical D6/D7 UART pins.
Can I run this on battery power? Yes -- built-in LiPo charge management via a JST pad, same as the rest of the XIAO line.
Should I use the Arm or RISC-V cores? Arm Cortex-M33, for nearly every project -- it's what ships active by default and has meaningfully better library and tooling support right now.
Why would I pick this over a plain Raspberry Pi Pico 2? Purely for size -- the Pico 2 has more GPIO (26 versus 19) and no need for external battery hardware considerations, but the XIAO RP2350 is a fraction of the footprint.
Where to Go From Here
Once the 19-pin layout and the separate UART-versus-USB distinction feel familiar, the hardware security features are worth exploring next for anything meant to move past a one-off prototype toward a small production run. From there, if a project ends up needing WiFi or Bluetooth after all, an ESP32-based XIAO board runs a similar compact form factor with wireless built in -- just with fewer GPIOs to work with.