August 7, 2025

RP2350 A4 Stepping: Why Raspberry Pi Pico’s Latest Upgrade Changes Everything

Raspberry Pi recently introduced the RP2350 A4 stepping, bringing critical enhancements to its flagship dual-core microcontroller. With security improvements, resolved hardware issues, and added features, the RP2350 A4 stepping isn't just another incremental update, it's transformative. But what exactly has changed, and how will it impact your Raspberry Pi Pico projects?

Let’s dive into the details.

What Is the RP2350 A4 Stepping?

The RP2350 A4 stepping is the latest iteration of Raspberry Pi's powerful dual-core MCU, designed to correct significant hardware and security issues identified in earlier versions (particularly the A2 stepping). This update provides comprehensive improvements, delivering both enhanced security and optimized hardware performance, making it a must-have upgrade for serious developers and embedded systems designers alike.

If you're connecting the RP2350 to retro computing hardware, there's good news: after extensive testing, the RP2350 is now officially 5V tolerant!

Can My Current Pico Projects Run on the New A4 Stepping?

Absolutely! Because A4 is a pin-compatible, drop-in replacement, your existing Pico designs work right away, often with nothing more than a rebuild on the latest SDK. Here are four examples you can migrate today:

Pico Smart Automation Controller – A DIY home-automation hub that enables intelligent control for sensors, relays, and devices.
Pico Macro Keyboard – A customizable USB HID keypad a.k.a macro pad built using the Raspberry Pi Pico 2.
Avocaudio – Tiny Community Audio Board – A tinyML board designed for extensive audio data collection across various tinyML applications.
Raspberry Pi Pico 2 Shield Template – A ready-made “shield” PCB that mirrors the exact footprint and pin order of the Pico 2, much like an Arduino shield.

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How Can I Tell If I Have the A2 or A4 Stepping?

You can identify the stepping version from the marking on the top surface of the chip, as illustrated below.

Do Pinouts Change with the RP2350 A4 Stepping?

No, great news for hardware engineers! The pin configuration and layout of the RP2350 A4 stepping remain identical to earlier versions, making it a perfect drop-in replacement. You can upgrade existing hardware designs without any modifications to your PCB layouts.

Below, I've included a detailed pinout mapping for quick reference.

GPIO Pins

Name	QFN-60	QFN-80	Type	Power Domain	Description
GPIO0	2	77	Digital IO (FT)	IOVDD	User IO
GPIO1	3	78	Digital IO (FT)	IOVDD	User IO
GPIO2	4	79	Digital IO (FT)	IOVDD	User IO
GPIO3	5	80	Digital IO (FT)	IOVDD	User IO
GPIO4	7	1	Digital IO (FT)	IOVDD	User IO
GPIO5	8	2	Digital IO (FT)	IOVDD	User IO
GPIO6	9	3	Digital IO (FT)	IOVDD	User IO
GPIO7	10	4	Digital IO (FT)	IOVDD	User IO
GPIO8	12	6	Digital IO (FT)	IOVDD	User IO
GPIO9	13	7	Digital IO (FT)	IOVDD	User IO
GPIO10	14	8	Digital IO (FT)	IOVDD	User IO
GPIO11	15	9	Digital IO (FT)	IOVDD	User IO
GPIO12	16	11	Digital IO (FT)	IOVDD	User IO
GPIO13	17	12	Digital IO (FT)	IOVDD	User IO
GPIO14	18	13	Digital IO (FT)	IOVDD	User IO
GPIO15	19	14	Digital IO (FT)	IOVDD	User IO
GPIO16	27	16	Digital IO (FT)	IOVDD	User IO
GPIO17	28	17	Digital IO (FT)	IOVDD	User IO
GPIO18	29	18	Digital IO (FT)	IOVDD	User IO
GPIO19	31	19	Digital IO (FT)	IOVDD	User IO
GPIO20	32	20	Digital IO (FT)	IOVDD	User IO
GPIO21	33	21	Digital IO (FT)	IOVDD	User IO
GPIO22	34	22	Digital IO (FT)	IOVDD	User IO
GPIO23	35	23	Digital IO (FT)	IOVDD	User IO
GPIO24	36	25	Digital IO (FT)	IOVDD	User IO
GPIO25	37	26	Digital IO (FT)	IOVDD	User IO
GPIO26_ADC0	40		Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO27_ADC1	41		Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO28_ADC2	42		Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO29_ADC3	43		Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO26		27	Digital IO (FT)	IOVDD	User IO
GPIO27		28	Digital IO (FT)	IOVDD	User IO
GPIO28		36	Digital IO (FT)	IOVDD	User IO
GPIO29		37	Digital IO (FT)	IOVDD	User IO
GPIO30		38	Digital IO (FT)	IOVDD	User IO
GPIO31		39	Digital IO (FT)	IOVDD	User IO
GPIO32		40	Digital IO (FT)	IOVDD	User IO
GPIO33		42	Digital IO (FT)	IOVDD	User IO
GPIO34		43	Digital IO (FT)	IOVDD	User IO
GPIO35		44	Digital IO (FT)	IOVDD	User IO
GPIO36		45	Digital IO (FT)	IOVDD	User IO
GPIO37		46	Digital IO (FT)	IOVDD	User IO
GPIO38		47	Digital IO (FT)	IOVDD	User IO
GPIO39		48	Digital IO (FT)	IOVDD	User IO
GPIO40_ADC0		49	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO41_ADC1		52	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO42_ADC2		53	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO43_ADC3		54	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO44_ADC4		55	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO45_ADC5		56	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO46_ADC6		57	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input
GPIO47_ADC7		58	Digital IO / Analog	IOVDD / ADC_AVDD	User IO or ADC input

QSPI Pins

Name	QFN-60	QFN-80	Type	Power Domain	Reset	Description
QSPI_SD3	55	70	Digital IO	QSPI_IOVDD	Pull-Up	QSPI data
QSPI_SCLK	56	71	Digital IO	QSPI_IOVDD	Pull-Down	QSPI clock
QSPI_SD0	57	72	Digital IO	QSPI_IOVDD	Pull-Down	QSPI data
QSPI_SD2	58	73	Digital IO	QSPI_IOVDD	Pull-Up	QSPI data
QSPI_SD1	59	74	Digital IO	QSPI_IOVDD	Pull-Down	QSPI data
QSPI_SS	60	75	Digital IO	QSPI_IOVDD	Pull-Up	QSPI chip select / USB BOOTSEL

Crystal Oscillator Pins

Name	QFN-60	QFN-80	Type	Power Domain	Description
XIN	21	30	Analogue (XOSC)	IOVDD	Crystal oscillator; XIN may also be driven by a square-wave source
XOUT	22	31	Analogue (XOSC)	IOVDD	Crystal oscillator

Misc Pins

Name	QFN-60	QFN-80	Type	Power Domain	Reset	Description
RUN	26	35	Digital In (FT)	IOVDD	Pull-Up	Chip enable / reset_n
SWCLK	24	33	Digital In (FT)	IOVDD	Pull-Up	Serial Wire Debug clock
SWDIO	25	34	Digital IO (FT)	IOVDD	Pull-Up	Serial Wire Debug data

USB Pins

Name	QFN-60	QFN-80	Type	Power Domain	Description
USB_DP	52	67	USB IO	USB_QTP_VDD	USB Data +; 27 Ω series resistor required for USB operation

What’s New in the RP2350 A4 Stepping?

This stepping addresses several critical issues and introduces highly requested features:

GPIO Leakage Bug Fixed: Resolves the notorious RP2350 erratum 9, removing unwanted current leakage on GPIO pins. As a result, external resistors are no longer required to pull inputs low, though they may safely be retained in existing designs.
Enhanced Security: Addresses boot ROM exploits, OTP corruption, glitch vulnerabilities, and provides hardened AES encryption for secure applications.
Integrated Flash Versions: Introduction of RP2354A/B variants with built-in 2 MB flash, simplifying hardware design and lowering production complexity.
Official 5V GPIO Tolerance: Easier interfacing with legacy and retro-computing hardware without needing additional level shifting.

Why Does the A4 Stepping Matter to You?

Goodbye GPIO Leakage. No more worrying about external workarounds, your designs become simpler, cheaper, and more reliable.
Stronger Security from the Ground Up. Hardened security improvements protect your products from known vulnerabilities, ensuring safer deployments, particularly important in IoT, industrial, and sensitive embedded projects.
Simplified Hardware Design. The RP2354 integrated-flash variant significantly reduces design complexity, saving PCB space and manufacturing costs.
Wider Compatibility. Official support for 5 V GPIO levels unlocks compatibility with more devices, sensors, and legacy systems without extra complexity.

Will the A2 stepping be discontinued?

Raspberry Pi already stopped manufacturing the A2 stepping, shifted all production exclusively to A4, and removed remaining A2 inventory from distribution channels. The A4 stepping is a direct, drop-in replacement for A2, so you shouldn't encounter any issues transitioning to the newer version.

How Can You Upgrade to the RP2350 A4 Stepping?

Follow these simple steps to leverage the power of RP2350 A4 in your Raspberry Pi Pico projects:

Update your Pico SDK to version 2.1.0 or newer (recommended: 2.2.0).
Rebuild your firmware using the latest SDK to ensure compatibility and utilize new security features.
Switch to RP2350 A4 stepping hardware fully compatible with existing designs but with improved security and reliability.

Availability and Pricing

RP2350A/B A4 Stepping: Now widely available through official Raspberry Pi distributors.
RP2354 Integrated Flash Variants: Available soon at around $1.30 to $1.40 per chip, simplifying your designs and saving costs.

Final Thoughts

The RP2350 A4 stepping significantly upgrades the potential of Raspberry Pi Pico-based designs. Enhanced security, hardware reliability, simpler designs, and broad compatibility make this stepping a turning point for professional and hobbyist projects alike.

Explore our Featured Projects page to discover more Raspberry Pi projects and fresh ideas that will jump-start your next hardware prototype.

Discover Featured Projects

A curated collection of PCB and hardware projects crafted by our talented Flux community.

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Jharwin Barrozo

Jharwin is an electronics engineer mainly focused on satellites. He built his own ground station using Flux to monitor RF activities on the International Space Station. Find him on Flux @jharwinbarrozo

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