How to get raw incoming I2C packet on Arduino Portenta?

[GrandPete]

ok that is much clear.
But sorry I didn't know a module may have more than one adress (at the same time) excluding the special "call every one on the line" operation.

There is a I2C scanner function, surely in example for wire library or other. I try to find a proper link and edit my post.

You compile the sketch on your master and let it play (with wiring ok between master and slave). It will call every possible I2C adress and wait for a response, then print on serial monitor the results.
Could be a good idea to test.

EDIT: one example of I2C scanner quoted in this forum

I2c scanner prints I and sht20 not working

im trying to use sht20 sensor for my project but it only works sometimes and not consistently sometimes it will and then the serial monitor will not work and freeze. i tried to use i2c scanner but it only prints I // -------------------------------------- // i2c_scanner // // Version 1 // This program (or code that looks like it) // can be found in many places. // For example on the Arduino.cc forum. // The original author is not know. // Version 2, Juni 2012, Using Arduino 1.0.1 //…

https://gist.github.com/tfeldmann/5411375