Revised Raspberry Pi RP2350 A4 Stepping Exposes E9 Current Drain Glitch
The Raspberry Pi community has received good news regarding the RP2350 Microcontroller Unit (MCU). A significant issue, known as erratum 9 (E9), has been causing GPIO input buffer current leakage. This problem, characterised by an internal weak pull-up in the pins configured as input with input buffer enabled, has been causing substantial current leakage.
As of July 29, 2024, Raspberry Pi has addressed this issue with the release of the new A4 stepping of the RP2350 MCU. According to a Product Change Note from Raspberry Pi, the fix involves both hardware correction, implemented in an internal A3 stepping (not publicly released), and software (bootrom) fixes in the A4 stepping. This means that the new A4 chips now resolve the leakage problem without the need for external hardware workarounds like pull-down resistors.
Prior to the A4 stepping release, users had to mitigate this issue by adding external pull-down resistors or other workarounds to prevent excessive current leakage on input pins. However, with the updated silicon from the A4 stepping and the updated bootrom, these external measures are no longer necessary. The revised RP2350 datasheet dated July 29, 2024, confirms these fixes and updates regarding the issue.
In summary, the current solution to the RP2350 GPIO input leakage issue (E9) is to use the A4 stepping RP2350 MCU, which includes the necessary hardware and software fixes. For earlier defective steppings (A2), external pull-downs and other workaround circuits remain the method to control leakage until newer stepping chips are available.
This development marks a significant step forward for the Raspberry Pi community, offering a way to overcome the E9 bug without the need for complex workarounds. While the E9 saga may not be completely over, this update provides a clear path for those using the RP2350 MCU.
With the latest release of the A4 stepping RP2350 Microcontroller Unit (MCU) by Raspberry Pi, the issue of hacking (addressing) the erratum 9 (E9) causing GPIO input buffer current leakage in hardware technology is now significantly mitigated. Previously, users had to employ external hardware workarounds such as pull-down resistors to combat excessive current leakage, but with the updated A4 chips, these measures are no longer required.
