[BradAMiller]

That's curious. The Vex code is identical to the FRC code, and all it does is call printf.

Here's a thought... Microchip upgraded their library at one point a few years ago and improved the printf support. It may be that you are using an older version of their library with printf on the Vex side.

You could get the source code (included with the C18 install) of the printf function and add it to your Vex project to make that work. But if you were just prototyping on Vex and the real program is working now, it may not matter.