How do you have vex cortex work with arudino?

I am trying to have vex cortex and arudino work to gather for example, I want my vex to do the driving and have the arudino tell the vex to stop driving when detecting a wall from the arudino. Just a simple command for the vex robot.

In general, Cortex supports many analog and digital sensors that work with Arduino, like the ultrasonic sensor, so you could simply connect them directly to the Cortex without a need for Arduino.

However, if you must have Arduino for some reason, then you could use Cortex UART serial port for communication.

These two threads have relevant discussion, pinouts, and code examples: