About SDA Waveform in I3C Open-Drain Mode

[jad1]

Hello,

I am working on a NUCLEO-H503RB board and communicating with two LSM6DSO devices over an I3C bus operating in I2C Mixed Mode.

When the bus is running in Open-Drain mode, I observe the following waveform characteristics on the SDA line:

1. When SCL transitions from High to Low, SDA exhibits a momentary voltage drop.
2. During the SDA pull-up (charging) phase, the signal does not follow a smooth RC charging curve. Instead, it initially rises slowly and then suddenly jumps to a higher voltage level (VH).

SDA waveform during I3C communication

SDA waveform during I2C communication (Open-Drain mode)

Could anyone help explain the possible causes of these behaviors? Are they related to I3C/I2C bus characteristics, device handoff timing, pull-up configuration, parasitic capacitance, or measurement effects?

Any suggestions or insights would be greatly appreciated.

Thank you.

Best regards,

[mƎALLEm]

Hello,

What pull-up resistors value you set for SDA and SCL?