Issues with the Raspberry Pi Pico 2, Raspberry Pi RP2350 Deepen as Initiatives Hit By Erratum E9

Raspberry Pi’s new RP2350 microcontroller household continues to be the main target of appreciable troubleshooting this week, as builders more and more run into the side-effects of a design flaw often known as erratum RP2350-E9 — with the consequence that some are cancelling designs constructed across the new chip, a minimum of till a brand new stepping is launched with the fault mounted.

Raspberry Pi unveiled the RP2350, a quad-core dual-architecture successor to the favored RP2040 and its first half to function RISC-V cores, again in early August, having offered early entry to a variety of {hardware} companions to design their very own boards to sit down alongside the Raspberry Pi Pico 2. Sadly, all has not been clean with the system’s launch: the invention of a {hardware} fault, often known as erratum RP2350-E9, which causes general-purpose enter/output (GPIO) pins to “latch” at across the 2V mark has been the reason for appreciable consternation amongst designers and engineers.

“[I] discovered a silicon bug,” Harmful Prototypes’ Ian Lesnet defined of the difficulty, following his report of the identical to Raspberry Pi and its recording of the flaw as a proper erratum. “When a GPIO [General-Purpose Input/Output] pin is an enter with the pull-down resistor enabled, it acts like a bus maintain. We use the pull-down on the button, which connects to three.3V when pressed. Through the self-test urgent the button works, however then it by no means goes low once more, it sits at 2.15V…”

Lesnet had been working with the RP2350 for the Bus Pirate 5XL and Bus Pirate 6, constructing on his earlier RP2040-powered Bus Pirate 5 design. These, nevertheless, have now been shelved, a minimum of in the interim. “RP2350 primarily based Bus Pirate (6 & 5XL) manufacturing is paused,” he explains in an replace posted to Mastodon this week. “E9 errata seems extra expansive than reported in [the] datasheet, [and the] first batch of RP2350 Bus Pirates are in all probability DOA [Dead On Arrival]. RP2350 inputs appear to stay at ~2.1 volts with out pull-down/load of ~9k ohms/0.33mA.”

“BP makes use of pin pull-downs with open collector bus sorts as a result of it simplifies PIO [Programmable Input/Output] packages that run via 1.2-5 volt bidirectional buffers. I tried to appropriate for E9 primarily based on what was recognized on the time: by disabling pin pull-down and utilizing an exterior 100k pull-down resistor. Sadly, this in all probability wasn’t sufficient. As reported by […] others, the latch up would not appear restricted to when pull-downs are enabled. Any enter pin not held low with [a] ~9k resistor will stick at 2.1 volts after going excessive in a number of exams.

The issue, simpler to set off than the official erratum within the datasheet would counsel, has been confirmed by others together with CircuitPython core developer Dan Halbert and maker Tod Kurt, who has acknowledged that “I at the moment have a number of Pico-based initiatives that can’t use Pico 2/RP2350 due to this drawback” — whereas Agustín Gimenez Bernad has cancelled a work-in-progress effort to port his RP2040-based logic analyzer to the RP2350 as a direct results of the flaw. “In accordance with the official errata the lock solely occurs when the pull downs are enabled, you enter a excessive degree worth after which the GPIO begins outputting 2.1V,” he explains. “That does not sound too unhealthy however the actuality could be very completely different.”

“I have been testing it and even forcing the pulldowns to be disabled,” Bernad continues, “the PIO triggers the lock. On this state, the RP2350 is ineffective if it’s essential use the GPIOs to enter any knowledge. The one workaround offered is to disable the pins and allow them when you’ll learn and disable them after it to reset the pin standing, however as you may think about with the PIO that is unattainable, and even when it was doable the seize velocity can be diminished a lot that the analyzer can be completely ineffective. Sadly I need to cease the port to the Pico 2 till this example is solved.”

Raspberry Pi engineer James Hughes has issued temporary remark within the firm’s discussion board, confirming that the corporate is in discussions with the IP provider it blames for the fault within the chip — however, on the time of writing, the corporate was sticking with the outline of the flaw because it stands within the datasheet, and had not commented on the timing and even probability of a brand new stepping, which might resolve the issue in {hardware} moderately than in documentation.

events can monitor the progress of the investigation through the Raspberry Pi Pico GitHub Situation.