Hi,

I am experiencing I²C communication issues when using the DFRobot IIC-UART converter on a shared I²C bus. The issue appears as timeout errors or I/O error, and the bus stops responding. I'm using a Raspberry pi 5 as a master device.

I modified the Pyhton lib's init function, because I want to use a shared bus as a parameter to the constructor.

Setup and Connections

Raspberry Pi as I²C master (3.3V logic)

DFRobot IIC-UART converter connected via I²C

Pull-up resistors: 10kΩ on SDA/SCL

I²C speed: 50 kHz (also tested 400, 100 kHz)

Power supplied from external power supply (up to 5A)

Common ground

RST pin connected to 3v3

Observed Behavior

The I²C bus works initially but eventually becomes unresponsive.

If I disconnect the DFRobot IIC-UART converter, I can restart the I²C communication without rebooting, and the bus works fine.

If I reboot the Raspberry Pi, the issue does not occur again immediately, but occur after a few minutes (1-3 min), even if i dont even initialize the lib.

The issue persists across different I²C speeds (50 kHz, 400 kHz).

What I Have Tried

Running i2cdetect -y 1 shows multiple I²C addresses for the converter (as expected), but no conflicts.

Reducing I²C speed to 50 kHz and 10 kHz to handle potential clock stretching.

Adding stronger pull-up resistors (4.7Ω) instead of 10kΩ.

Disconnecting the converter resolves the issue.

Reloading the I²C driver (rmmod i2c_bcm2835 && modprobe i2c_bcm2835) sometimes helps temporary.

Questions

Has anyone encountered similar timeout issues with this module?

Could the converter be holding SDA LOW due to UART buffering?

Is there a known hardware or firmware issue when using this module on a shared I²C bus?

Would adding a GPIO-controlled reset circuit for the converter help?

Any insights or suggestions would be appreciated. Thanks in advance.

Thanks!