Connecting Arduino with Pixhawk


I have designed a 4wd robot chassis and need to control it using a Pixhawk. The setup I have is a Pixhawk 2.4.8 and an arduino based motor controller. I need to get data from Pixhawk. Kindly suggest on the following:

  1. There is an Arduino based motor controller with both I2C and UART ports. However I prefer using I2C since there is only one UART port on Arduino Uno. Should I use I2C or UART?
  2. How to send signals from the Pixhawk to Arduino to drive the motors?
  3. This the first time I am connecting the two. Are there any libraries to communicate between the two?
  4. What setup should I make in Mission Planner for the setup?

Kindly Help!

Anyone has any idea on this?