Hardcrash on Fruit Jam with I2C pin finding script

[FoamyGuy]

Adafruit CircuitPython 10.0.0-beta.0 on 2025-07-15; Adafruit Fruit Jam with rp2350b

With this code which is embedded in I2C page of many learn guides:

import board
import busio
from microcontroller import Pin


def is_hardware_i2c(scl, sda):
    try:
        p = busio.I2C(scl, sda)
        p.deinit()
        return True
    except ValueError:
        return False
    except RuntimeError:
        return True


def get_unique_pins():
    exclude = [
        getattr(board, p)
        for p in [
            # This is not an exhaustive list of unexposed pins. Your results
            # may include other pins that you cannot easily connect to.
            "NEOPIXEL",
            "DOTSTAR_CLOCK",
            "DOTSTAR_DATA",
            "APA102_SCK",
            "APA102_MOSI",
            "LED",
            "SWITCH",
            "BUTTON",
            "ACCELEROMETER_INTERRUPT",
            "VOLTAGE_MONITOR",
            "MICROPHONE_CLOCK",
            "MICROPHONE_DATA",
            "RFM_RST",
            "RFM_CS",
            "RFM_IO0",
            "RFM_IO1",
            "RFM_IO2",
            "RFM_IO3",
            "RFM_IO4",
            "RFM_IO5",
            "TFT_I2C_POWER",
            "NEOPIXEL_POWER",
        ]
        if p in dir(board)
    ]
    pins = [
        pin
        for pin in [getattr(board, p) for p in dir(board)]
        if isinstance(pin, Pin) and pin not in exclude
    ]
    unique = []
    for p in pins:
        if p not in unique:
            unique.append(p)
    return unique


for scl_pin in get_unique_pins():
    for sda_pin in get_unique_pins():
        if scl_pin is sda_pin:
            continue
        if is_hardware_i2c(scl_pin, sda_pin):
            print("SCL pin:", scl_pin, "\t SDA pin:", sda_pin)

It results in hard crash, seemingly always after the same pair of pins:

Auto-reload is off.
code.py output:
SCL pin: board.A1        SDA pin: board.A0
SCL pin: board.A1        SDA pin: board.A4
SCL pin: board.A1        SDA pin: board.BUTTON1
SCL pin: board.A1        SDA pin: board.BUTTON2
SCL pin: board.A1        SDA pin: board.CKN
SCL pin: board.A1        SDA pin: board.D1N
SCL pin: board.A1        SDA pin: board.D8
SCL pin: board.A1        SDA pin: board.I2S_DIN
SCL pin: board.A1        SDA pin: board.MISO
SCL pin: board.A1        SDA pin: board.SDA
SCL pin: board.A3        SDA pin: board.A2
SCL pin: board.A3        SDA pin: board.D0N
SCL pin: board.A3        SDA pin: board.D10
SCL pin: board.A3        SDA pin: board.D2N
SCL pin: board.A3        SDA pin: board.D6
SCL pin: board.A3        SDA pin: board.ESP_CS
SCL pin: board.A3        SDA pin: board.ESP_RESET
SCL pin: board.A3        SDA pin: board.I2S_BCLK
SCL pin: board.A3        SDA pin: board.SCK
SCL pin: board.A3        SDA pin: board.SDIO_DATA2
SCL pin: board.A3        SDA pin: board.USB_HOST_DATA_MINUS

[11:33:11.633] Disconnected
[11:33:12.634] Connected
Auto-reload is off.
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Hard fault: memory access or instruction error.
Please file an issue with your program at github.com/adafruit/circuitpython/issues.
Press reset to exit safe mode.

Press any key to enter the REPL. Use CTRL-D to reload.

I found that if I add USB_HOST_DATA_MINUS to the exclude list then it does not hard crash and is able to successfully complete the pin search.

[dhalbert]

I don't have my Fruit Jam yet (tomorrow, probably). I tested your exact program on a Metro RP2350B running 10.0.0-beta.0 and beta.2, and it did not hard-crash. I then loaded the Fruit Jam firmware on it, both beta.0 and beta.2, and it did also not crash in either case. So this is a bit strange.

Could you re-test with beta.2, just in case?

[FoamyGuy]

It does still occur for me under 10.0.0-beta.2.

However I have noticed another weird quirk about it. If I run the code with USB_HOST_DATA_MINUS in the exclude list and let it finish, then modify the code to remove USB_HOST_DATA_MINUS from the list and Ctrl-C / Ctrl-D it seems to run without the hard crash and complete successfully including printing some pin pairs that have USB_HOST_DATA_MINUS.

All testing on REV C hardware.

[samblenny]

Possible this isn't relevant, but just in case... I got a different I2C safe mode thing yesterday on my Fruit Jam rev B (error message about missing pull ups). That one seemed to be caused by leaving my HDMI capture card plugged into the Fruit Jam (I2C EDID EEPROM) without having the capture card plugged into its own USB power source. Apparently the capture card was loading the I2C pins and confusing the CircuitPython core.

Have you checked to see if reproducing your issue has any sensitivity to whatever peripherals may be connected to the board?

[FoamyGuy]

This did originally occur while the Fruit Jam was connected via HDMI to my capture card (though fully powered and connected to computer), and actually an AHT20 connected via STEMMA cable as well.

I removed the AHT20 before the test on beta-2, and have unplugged the HDMI cable now as well, and confirmed I still the same hard crash with nothing else plugged in to the fruit jam beyond the USB C cable powering it and providing serial console.

[samblenny]

I was able to reproduce this on my Fruit Jam rev B by running your code above on 10.0.0-beta.2. Serial output made it this far before the board reset and I got a "disk not ejected properly" error from macOS:

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
SCL pin: board.A1        SDA pin: board.A0
SCL pin: board.A1        SDA pin: board.A4
SCL pin: board.A1        SDA pin: board.BUTTON1
SCL pin: board.A1        SDA pin: board.BUTTON2
SCL pin: board.A1        SDA pin: board.CKN
SCL pin: board.A1        SDA pin: board.D1N
SCL pin: board.A1        SDA pin: board.D8
SCL pin: board.A1        SDA pin: board.I2S_DIN
SCL pin: board.A1        SDA pin: board.MISO
SCL pin: board.A1        SDA pin: board.SDA
SCL pin: board.A1        SDA pin: board.SD_MISO
SCL pin: board.A3        SDA pin: board.A2
SCL pin: board.A3        SDA pin: board.D0N
SCL pin: board.A3        SDA pin: board.D10
SCL pin: board.A3        SDA pin: board.D2N
SCL pin: board.A3        SDA pin: board.D6
SCL pin: board.A3        SDA pin: board.ESP_CS
SCL pin: board.A3        SDA pin: board.ESP_RESET
SCL pin: board.A3        SDA pin: board.I2S_BCLK
SCL pin: board.A3        SDA pin: board.SCK
SCL pin: board.A3        SDA pin: board.SD_SCK
SCL pin: board.A3        SDA pin: board.SDIO_DATA2
SCL pin: board.A3        SDA pin: board.USB_HOST_DATA_MINUS

After reset, the board came up with the 3 yellow blinks on the neopixel thing.
When I reconnected to the serial monitor, it said:

Auto-reload is off.
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Hard fault: memory access or instruction error.
Please file an issue with your program at github.com/adafruit/circuitpython/issues.
Press reset to exit safe mode.

Press any key to enter the REPL. Use CTRL-D to reload.

[samblenny]

Does this reproduce on a Metro RP2350 if you connect a USB hub breakout to the USB host header?

[FoamyGuy]

I connected a CH334F and tried all permutations of: Metro PSRAM / NO PSRAM, Metro firmware / Fruit Jam firmware. All on beta-2. None of them hard crashed running the same code.

[samblenny]

Huh... that's weird. What else would be different about the two boards? Maybe the Fruit Jam's I2S DAC, the AirLift C6, or the IR receiver?