I2C and Telemetry ports

I’m currently working on a project where we are using 2 piwhawks and some external sensors connected through the I2C port, and no matter what we tried we are not able to make the logging of the data.
We read some manuals, forums, etc, and we already tried using QGroundControl and Mission Planner to get the data but apparently the information is not being transmitted.
We also connected the external sensors to an Arduino board, and then tried to connect the Arduino to the Pixhawk through the telemetry port and start the transmission but nothing seems to work, so I’m pretty sure that I’m making some mistakes in the configuration.
Can anybody tell me what I’m doing wrong?