[Foster]

I've had good luck connecting things to the serial ports. As noted above you need to take the VEX TX and put it to the other device RX.

I have a breakout box that puts an LED on the line and at low baud rates I can see the LED flicker as the characters go by.

When looking for characters from the Arduino (TX) port to the VEX input (RX) port check the USART status buffer. It will tell you if you got frame errors (bitrates wrong).

Good luck,
Foster