There is an example on our web site that converts Decimal/Hexidecimal to its ASCII Character. You can find with the following path (I also attached them):
ni.com>>Technical Support>>Advanced Search...Check the Example Programs box and search for "decimal convert ascii"
If this is not what you are looking for, there are several example programs and resources available I suggest searching. Good Luck!
Best Regards,
Chris D
Applications Engineer
Nationl Instruments