Thanks to both :) @ajb2k3 : as written also by @felmue I want to power all my system with 3.3V so there won't be around any 5V at all ! Of course I need to check the specific schematic in order to understand what to bypass, but my question was if the white enclosure of M5Stack modules (like the I2C hub, or the heart rate sensor) can be easily open - without damaging / breaking them - or not (is there something like a screw?). Any clue about that? thanks!