A Surprise Hardware Bug in Raspberry Pi's RP2350 Leads to Unexpected Pull-Down Behavior

Raspberry Pi has confirmed a bug in the new RP2350 microcontroller family, which causes pins to freeze outputting 2.15V when configured as inputs using the internal pull-down resistors — tied, it seems, to changes made by a vendor to an off-the-shelf fault tolerant pad IP block.

“[I] found a silicon bug,” Dangerous Prototypes’ Ian Lesnet explains of the issue, which has been confirmed as an erratum in Raspberry Pi’s official documentation for the newly-launched dual-architecture RP2350 microcontroller family. “When a GPIO [General-Purpose Input/Output] pin is an input with the pull-down resistor enabled, it acts like a bus hold. We use the pull-down on the button, which connects to 3.3V when pressed. During the self-test pressing the button works, but then it never goes low again, it sits at 2.15V…”