from Hacker News

The worsening Raspberry Pi RP2350 E9 erratum situation

by irdc on 9/8/24, 9:33 AM with 19 comments

  • by iracigt on 9/8/24, 2:37 PM

    After this was published, RPi concluded the problem was a leakage current and updated the datasheet [1]. Roughly, a tiny trickle of electricity, about 100 microamps, flows out via the pin when it shouldn't. This can raise the voltage to around 2V unless you provide a path to drain it away.

    I've ordered one and am confident for anything I'd do it's not an issue. Usually any input I have is connected directly to the output of something else and that provides the path for the leakage current. If that isn't true, e.g. a button, then I'm using a pull-up and thus also not affected. Certain analog measurements could be affected, but again not if they have a low impedance (i.e. strong) source. The current is around 100 microamps so it's not stressing the source much.

    It's unfortunate that this is happening in the chip that so massively improved the low power sleep states. Designs needing wake from sleep on pin change with an active high / inactive high-z signal are not going to be good. That requires a strong external pulldown and will be constantly burning those 100ish microamps. That doesn't sound like much, but it's a lot of power for being asleep.

    Still I'm very excited for the improved CPU performance and even more RAM. Once mine arrives I'm going to see how much faster it can do some fixed point DSP than the RP2040.

    [1] https://github.com/raspberrypi/pico-feedback/issues/401#issu...

  • by irdc on 9/8/24, 9:35 AM

    See https://community.element14.com/products/raspberry-pi/f/foru... for some really wild scope traces demonstrating the soft latching problem (hat tip to Ian in the Hackaday comments section).

  • by jsheard on 9/8/24, 2:12 PM

    I wonder if the self-imposed deadline of announcing it at DEFCON caused them to rush validation more than they would have otherwise. If not for that then they could have quietly delayed the announcement until the next stepping was ready, and nobody would have been the wiser.

  • by 1-6 on 9/8/24, 2:34 PM

    RPi should have never gone public on the stock exchange.

  • by throwaway81523 on 9/8/24, 9:43 AM

    Ehh these were in stock at Adafruit a couple days ago and I decided not to order due to having no immediate use for them. I think I'll wait. The main bug I remember in the RP2040 was some mistake in the ADC causing precision loss. The RP2040 is ridiculously powerful for an MCU so I think most of us either can do without the RP2350 for a while, or really need a Linux board anyway.