Core adafruit_bus_device is incompatible with Debug_I2C

[FoamyGuy]

CircuitPython version and board name

Adafruit CircuitPython 10.1.2-16-ga2532bd537-dirty on 2026-03-04; Adafruit Fruit Jam with rp2350b

Code/REPL

import adafruit_lis3dh
import board
import digitalio

from adafruit_debug_i2c import DebugI2C

i2c = DebugI2C(board.I2C())
int1 = digitalio.DigitalInOut(board.D8)
accelerometer = adafruit_lis3dh.LIS3DH_I2C(i2c, address=0x19, int1=int1)

print(accelerometer.acceleration)

for i in range(2):
    print(accelerometer.acceleration)

Behavior

Raises this exception when the driver that Debug_I2C instance is passed to attempts to create I2CDevice

code.py output:
Traceback (most recent call last):
  File "code.py", line 34, in <module>
  File "/lib/adafruit_tcs3430.py", line 258, in __init__
AttributeError: 'DebugI2C' object has no attribute 'probe'

Like from this line: https://github.com/adafruit/Adafruit_CircuitPython_TCS3430/blob/887075088e92cabdd165c9ddbe127f8a98c786dc/adafruit_tcs3430.py#L279 (line numbers differ because I had different version of driver on device)

Description

No response

Additional information

I think Debug_I2C was made for the python implementation of adafruit_bus_device and perhaps never updated for the core implementation, or perhaps the core implementation is missing something internally that the python one has.

If I force the driver to use the python implementation by changing the name of the library directory and import code like this:

from adafruit_bus_device_py import i2c_device

Then it succeeds and does print all of the debugging traffic.

[tannewt]

Does it work if you add probe() to DebugI2C?

[FoamyGuy]

I'm not really sure what should be inside the implementation of probe() I tried adding a blank function to DebugI2C:

    def probe(self):
        pass

And it raises a different exception that points to the same line where I2CDevice gets created:

ode.py output:
Traceback (most recent call last):
  File "code.py", line 35, in <module>
  File "/lib/adafruit_tcs3430.py", line 258, in __init__
TypeError: function takes 1 positional arguments but 2 were given

Code done running.

Interestingly I don't think DebugI2C has a probe attribute even when using the python implementation of adafruit_bus_device. I tested with the python implementation subb'd in and printed the fields with:

i2c = DebugI2C(board.I2C())
print(dir(i2c))

It prints this list which does not contain probe but somehow gets past the I2CDevice init that raises the exception when core implementation is used

['__class__', '__enter__', '__exit__', '__init__', '__module__', '__qualname__', '__dict__', 'deinit', 'readfrom_into', 'scan', 'try_lock', 'unlock', 'writeto', 'writeto_then_readfrom', '_i2c', '_writeto_then_readfrom']

[FoamyGuy]

I have realized that board.I2C() is the object that actually does have probe(). And of course it has it regardless of whether python or core implementation of adafruit_bus_device is used.

I think the thing causing the difference in behavior is that the core implementation is seemingly trying to load the method probe() here:

circuitpython/shared-module/adafruit_bus_device/i2c_device/I2CDevice.c

Line 45 in 39597dc

mp_load_method(self->i2c, MP_QSTR_probe, dest);

But the python implementation doesn't seem to use that function. It has a private __probe_for_device() function, but inside it just directly reads/writes the bus. It does not appear to use probe() function specifically
https://github.com/adafruit/Adafruit_CircuitPython_BusDevice/blob/69ebda79d40d0e74c01e4f1aa293f219b8c7e086/adafruit_bus_device/i2c_device.py#L159-L178

I was able to get DebugI2C to work successfully by adding probe() function to it that defers to the I2C object probe() function.

self.probe = self._i2c.probe

I'll PR that change and close this once it's merged.