Inside the RP2350 A4 Revision: Key Bug Fixes and a Challenge for Developers
The world of embedded electronics is buzzing with anticipation for the Raspberry Pi RP2350, the powerful successor to the wildly popular RP2040 microcontroller. As with any new piece of complex silicon, the journey from initial design to mass production involves rigorous testing and refinement. The latest step in this journey is the A4 silicon revision, a critical update that addresses key bugs and brings the chip one step closer to its final, production-ready form.
For developers, engineers, and hobbyists eager to get their hands on this new hardware, understanding these revisions is crucial. Let’s dive into what the A4 update entails, the significant fixes it brings, and how the community is being called upon to ensure its robustness.
The Importance of Silicon Revisions
Creating a new microcontroller is an incredibly complex process. The first versions of a chip, often called “A0” or “A1” silicon, are engineering samples. While functional, they almost always contain minor flaws or deviations from the design specification, known as “errata.”
Through a meticulous process of internal testing and feedback from early partners, engineers identify and fix these bugs in subsequent hardware revisions. Each new version—A2, A3, and now A4—represents a more stable, reliable, and refined product. The A4 revision of the RP2350 signifies a major milestone in maturity, addressing several issues discovered in earlier samples.
Key Fixes in the RP2350 A4 Silicon
The A4 revision incorporates several important fixes that will improve performance, stability, and power efficiency. Here are some of the most notable improvements:
Enhanced USB Controller Stability: Early silicon samples sometimes exhibited intermittent issues with high-speed USB data transfers and device enumeration, particularly under heavy bus load. The A4 revision includes fixes to the USB controller’s physical layer (PHY) and protocol handling, resulting in significantly more reliable USB connectivity. This is a critical fix for applications relying on robust data logging or communication.
Improved ADC Linearity and Noise Reduction: For projects requiring precise analog measurements, the Analog-to-Digital Converter (ADC) is paramount. This update refines the ADC’s internal voltage references and sampling circuitry, leading to better linearity across the input range and reduced noise in measurements. This means more accurate sensor readings and more reliable data acquisition.
PIO State Machine Timing Corrections: The Programmable I/O (PIO) is one of the most powerful features of Raspberry Pi silicon, allowing developers to create custom hardware interfaces. The A4 revision corrects a subtle timing issue in the PIO state machines that could cause jitter in high-frequency custom protocols. This fix ensures more deterministic and reliable performance for demanding applications like custom video signal generation or high-speed peripheral emulation.
Optimized Power Gating for Deep Sleep: Efficient power management is essential for battery-powered devices. Earlier revisions had minor current leakage in certain deep sleep configurations. The A4 update resolves this by optimizing the chip’s power gating, ensuring that power consumption in low-power modes meets the design specifications. This allows for longer battery life in portable and remote applications.
A Challenge to the Community: Find the Final Flaws
With these major fixes in place, the RP2350 is now considered highly stable. However, real-world applications often push hardware to its limits in ways that controlled lab tests cannot.
To that end, Raspberry Pi is issuing a challenge to the broader developer community. By getting A4 silicon samples into the hands of more engineers and makers, the goal is to uncover any remaining, obscure bugs that only manifest under unique or extreme conditions. This “crowdsourced” approach to validation is invaluable for ensuring the final product is as flawless as possible.
Developers are encouraged to stress-test the hardware, focusing on edge cases:
- Running all peripherals simultaneously.
- Operating at the extremes of the specified temperature range.
- Implementing complex, high-frequency PIO protocols.
- Testing power state transitions under heavy core load.
How to Check Your Chip Revision
If you are fortunate enough to have an RP2350 sample, identifying its revision is straightforward. The revision is typically marked on the chip’s packaging. Furthermore, the chip’s revision ID can often be read from a dedicated system register using software, allowing your firmware to identify the hardware it’s running on and apply any necessary workarounds for older silicon.
The move to the A4 revision is a clear signal that the RP2350 is nearing the finish line. For anyone planning to build products with this next-generation microcontroller, this update provides confidence that the underlying hardware is becoming a stable and reliable platform for innovation.
Source: https://go.theregister.com/feed/www.theregister.com/2025/07/29/raspberry_pi_rp2350_update/
