Hello daniel Paiva.
Yes it's possible to use the serial port of the controller cRIO-9012 to communicate with your third party instruments and to do that please take a look at the links below.
The first one will teach you how to install the necessary software to enable this connection. Remember that you need to have installed the NI-Serial and VISA drivers to perform this communiction on your development computer, to then find those items in the software installation proccess in the cRIO controller. After realize the software installation, go to the second link and take a look at the chapter 8 to understand how to use the serial port.
http://www.ni.com/gettingstarted/setuphardware/compactrio/pt/controllersoftware.htm
http://www.ni.com/pdf/products/us/fullcriodevguide.pdf
I hope this helps you to develop your application and any other further questions feel free to ask.
Regards.
Marcio Soares
Applications Engineer
National Instruments Brasil
www.ni.com/suporte