Hi Jesse,
This is a little subtle but bear with me.
When you read from the serial port and get a string, you ARE READING HEX!
I am guessing what you really want is an array of bytes that you can act on directly.
Wether it is an array of bytes or a string the data is the same. What is different is the representation.
The "type cast" (found on the advanced >>> data manipulation pallette) will let you change the represenation of your data.
You wire the data you want to change the representation of to the left input and a "type" into the top input. The "type" just tells LV what representation you want.
So...
drop a "type cast" on your diagram and wire the string to the left input. Wire a byte array to the top, and you are now free to work with t
he bytes using any number system you want (including HEX).
I hope this help,
Ben