# RP2350 A4 Stepping: Why Raspberry Pi Pico’s Latest Upgrade Changes Everything RP2350 A4 fixes GPIO bug, hardens security, adds 5 V tolerance and on-chip flash. See why every Pico project should migrate. Written by [Jharwin Barrozo](https://www.flux.ai/jharwinbarrozo) Published Aug 2025 - 8 min read [![](https://www.flux.ai/p/assets/blogs/rp2350-a4-stepping/main.webp)](#) ## 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: 1. [Pico Smart Automation Controller](https://www.flux.ai/vasy_skral/pico-smart-automation-controller-nextpcb-1-4-layer-standard-constraints) – A DIY home-automation hub that enables intelligent control for sensors, relays, and devices. 2. [Pico Macro Keyboard](https://www.flux.ai/flux/pico-macro-keyboard) – A customizable USB HID keypad a.k.a macro pad built using the Raspberry Pi Pico 2. 3. [Avocaudio – Tiny Community Audio Board](https://www.flux.ai/collinsemasi/avocaudio-a-tinyml-community-board-v1) – A tinyML board designed for extensive audio data collection across various tinyML applications. 4. [Raspberry Pi Pico 2 Shield Template](https://www.flux.ai/jharwinbarrozo/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. ### Discover Featured Projects A curated collection of PCB and hardware projects crafted by our talented Flux community. [ explore MORE projects ](https://www.flux.ai/p/projects) ### 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. [![rp2350A2 and rp2350A4 comparison](https://www.flux.ai/p/assets/blogs/rp2350-a4-stepping/rp2350a2-rp2350a4-comparison.webp)](#) ### 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. [![rp2350A and rp2350b pin mapping](https://www.flux.ai/p/assets/blogs/rp2350-a4-stepping/Raspberry-Pi-RP2350-Pin-Diagram.webp)](#) #### 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: 1. **Update your Pico SDK** to version 2.1.0 or newer (recommended: 2.2.0). 2. **Rebuild your firmware** using the latest SDK to ensure compatibility and utilize new security features. 3. **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](https://www.flux.ai/p/projects?categories=raspberrypi) 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. [ explore MORE projects ](https://www.flux.ai/p/projects) Let’s start building Build your big idea together with Flux. All you need to do is describe what you want to make, or what problem you want to solve. Flux will work with you to make it a reality. ![Close-up photo of a PCB made with Flux, with an ESP32 module, buttons, and a microSD slot.](https://www.flux.ai/p/assets/blogs/miscellaneous/sidebar-cta-pcb.webp) [Try it Free](https://www.flux.ai/signup) ## More in Component & Platform Guides [ ![A 3d model of arduino uno board](https://www.flux.ai/p/assets/blogs/arduino-getting-started/main.webp) ### Arduino Uno Basics: Beginner's Guide to Getting Started 15 Min Read](https://www.flux.ai/p/blog/arduino-uno-basics-beginners-guide-to-getting-started)[ ![ESP32 Board with its pinout label and diagram, each pin label and function on different colors](https://www.flux.ai/p/assets/blogs/esp32-pinout/main.webp) ### ESP32 Pinout Guide: Everything You Need to Know 11 Min Read](https://www.flux.ai/p/blog/esp32-pinout-everything-you-need-to-know)[ ![A raspberry pi 3B and zero boards laid out together showing graphical GPIO pinout](https://www.flux.ai/p/assets/blogs/raspberry-pi-guide/main.webp) ### Raspberry Pi Pinouts: A Comprehensive Guide 8 Min Read](https://www.flux.ai/p/blog/raspberry-pi-pinouts-a-comprehensive-guide)[ ![An arduino uno microcontroller board with its sketch code on Arduino IDE being used as background in a monitor.](https://www.flux.ai/p/assets/blogs/arduino-code-guide/main.webp) ### Arduino Code for Beginners: How to Write Your First Sketch 8 Min Read](https://www.flux.ai/p/blog/arduino-code-a-comprehensive-guide-for-beginners)[ ![Meet the Arduino Nano R4: Why Is This Tiny Upgrade So Big for Makers?](https://www.flux.ai/p/assets/blogs/arduino-nano-r4/main.webp) ### Meet the Arduino Nano R4: Why Is This Tiny Upgrade So Big for Makers? 6 Min Read](https://www.flux.ai/p/blog/meet-the-arduino-nano-r4-why-is-this-tiny-upgrade-so-big-for-makers)[ ![A microcontroller board with the words Arduino Pro Micro on it.](https://www.flux.ai/p/assets/blogs/arduino-pro-micro/main.webp) ### What is Arduino Pro Micro: a Comprehensive Introduction for Novices 5 Min Read](https://www.flux.ai/p/blog/what-is-arduino-pro-micro-a-comprehensive-introduction-for-novices)[ ![Schematic diagram of arduino uno board with all of its passive and active components](https://www.flux.ai/p/assets/blogs/arduino-uno-schematic-diagram/main.webp) ### Arduino Uno Schematic Diagram: A Comprehensive Guide 8 Min Read](https://www.flux.ai/p/blog/arduino-uno-schematic-diagram)[ ![Side by side comparison of the 3 powerful and most common Arduino microcontroller boards; Arduino Mega 2560, Arduino Uno and Arduino Micro.](https://www.flux.ai/p/assets/blogs/arduino-mega-uno-micro/main.webp) ### Arduino Mega vs. Uno vs. Micro: Key Differences 6 Min Read](https://www.flux.ai/p/blog/what-is-the-real-difference-arduino-mega-vs-micro-vs-uno)[ ![Different packages or footprint of famous atmega328p microcontroller with its pinout](https://www.flux.ai/p/assets/blogs/atmega328p-still-top-choice/main.webp) ### Why Atmega328p is Still a Top Choice for Microcontroller Projects in 2023 8 Min Read](https://www.flux.ai/p/blog/why-atmega328p-is-still-a-top-choice-for-microcontroller-projects-in-2023)[ ![ESP32 Chip in a dark background: A powerful microcontroller with integrated Wi-Fi and Bluetooth, driving IoT innovation with seamless connectivity.](https://www.flux.ai/p/assets/blogs/esp32-history/main.webp) ### Exploring ESP32: from History to Application 3 Min Read](https://www.flux.ai/p/blog/exploring-esp32-from-history-to-application)[ ![3d rendered of an ESP8266 microcontroller board, showing its compact size with the Wi-Fi module, chip antenna, and GPIO pins clearly visible, ideal for embedding wireless internet connectivity into DIY electronics projects.](https://www.flux.ai/p/assets/blogs/everything-about-esp8266/main.webp) ### ESP8266 Pinout Guide: Complete GPIO Reference & IoT Project Tips 10 Min Read](https://www.flux.ai/p/blog/esp8266-pinout-everything-you-need-to-know)[ ![Attiny85 chip in two different packages viewed on top, also showing pinout diagram](https://www.flux.ai/p/assets/blogs/attiny85/main.webp) ### Introduction to the ATtiny85 Microcontroller 12 Min Read](https://www.flux.ai/p/blog/introduction-to-the-attiny85-microcontroller)[ ![STM32 microcontroller chip overview – Why choose STM32? Discover STM32F4 ARM-based processors, optimized for performance with USB OTG, SWD, and UART support](https://www.flux.ai/p/assets/blogs/stm32-things-you-need-to-know/main.webp) ### STM32: Things You Need to Know 10 Min Read](https://www.flux.ai/p/blog/stm32-things-you-need-to-know)[ ![Arduino Nano Guide](https://www.flux.ai/p/assets/blogs/arduino-nano-guide/main.webp) ### Arduino Nano Guide 10 Min Read](https://www.flux.ai/p/blog/arduino-nano-guide)[ ![A top view photo of raspberry pi zero 2 w board](https://www.flux.ai/p/assets/blogs/pi-zero-2w/main.webp) ### Raspberry Pi Zero 2 W Review: a Powerful and Affordable Mini Computer 9 Min Read](https://www.flux.ai/p/blog/raspberry-pi-zero-2-w-review-a-powerful-and-affordable-mini-computer)[ ![Photos of Raspberry Pi Pico 2 PCB board and its predecessor Raspberry Pi Pico boards laid out with a text suggesting their key differences](https://www.flux.ai/p/assets/blogs/pi-pico-vs-pi-pico-2/main.webp) ### Raspberry Pi Pico 2 vs Pico: Key Differences and Upgrades 8 Min Read](https://www.flux.ai/p/blog/whats-new-in-the-raspberry-pi-pico-2-a-showdown-with-the-original-raspberry-pi-pico)[ ![Choosing the Right Platform to Build Your Project](https://www.flux.ai/p/assets/blogs/choosing-the-right-microcontroller/main.webp) ### Choosing the Right Platform to Build Your Project 9 Min Read](https://www.flux.ai/p/blog/choosing-the-right-platform-to-build-your-project)[ ![Raspberry pi boards and arduino boards laid out side by side.](https://www.flux.ai/p/assets/blogs/arduino-vs-raspberry-pi/main.webp) ### Arduino vs. Raspberry Pi: Key Differences and Which to Choose 8 Min Read](https://www.flux.ai/p/blog/arduino-vs-raspberry-pi-comparison)[ ![ESP32 boards and Arduino boards side by side, highlighting the comparison between these popular IoT microcontroller platforms.](https://www.flux.ai/p/assets/blogs/esp32-vs-arduino/main.webp) ### ESP32 vs Arduino: Key Differences & Which to Choose? 8 Min Read](https://www.flux.ai/p/blog/esp32-vs-arduino)[ ![arduino board and text suggesting this is all about the arduino map () function](https://www.flux.ai/p/assets/blogs/arduino-map-function/main.webp) ### How to Use the Arduino map() Function: A Complete Guide 4 Min Read](https://www.flux.ai/p/blog/how-to-use-the-arduino-map-function-a-complete-guide)[ ![A simplified schematic diagram illustrates how pull-up and pull-down resistors are utilized in microcontroller applications](https://www.flux.ai/p/assets/blogs/pull-up-down-resistors/main.webp) ### Understanding Pull-up and Pull-down Resistors: A Guide for Arduino and Microcontrollers 7 Min Read](https://www.flux.ai/p/blog/understanding-pull-up-and-pull-down-resistors-a-guide-for-arduino-and-microcontrollers)[ ![What Is an Open Circuit? Causes, Examples, and Troubleshooting](https://www.flux.ai/p/assets/blogs/what-is-an-open-circuit/main.webp) ### What Is an Open Circuit? Causes, Examples, and Troubleshooting 10 Min Read](https://www.flux.ai/p/blog/what-is-an-open-circuit) See All (22) ## Let’s start building. Let’s build your idea together. All you need to do is describe what you want to make, or what problem you want to solve. Flux will work with you to make it a reality. [Try it Free](https://www.flux.ai/signup) ![Close-up of a Flux-designed printed circuit board](https://www.flux.ai/p/assets/homepage-v2/mission-visual.webp)