thanks for your answer, but did you see my splitter on the pict? do you think this is not doing the job? for me I2C is a kind of bus and should work as this, no? maybe I'm totally wrong, but I use the same type of splitter on my Pixhawk, the difference is that it is connected directly to the I2C connector.
I have a message in MP Bad Lidar health, and 0 in the Range indicator, so I assume the connection part is ok, this is just with the serial protocol configuration that something must be wrong SERIAL_3 is for GPS and SERIAL_4 is for Frsky, so do I have to configure something specific for another SERIAL?