Hi Mughees,
Doing actual PWM off of the AUX (also called GPIO) would probably be challenging, especially without customizing the USRP RIO FPGA at all. Without FPGA modification, you have a limited amount of control over the pins. Assuming you're using LabVIEW, the LabVIEW USRP drive has a couple VIs in instr.lib/niUSRP called Get/Set GPIO Attribute you use to control the GPIO pins. I'd suggest reviewing Ettus' documentation for details on actually using them: http://files.ettus.com/manual/page_gpio_api.html.
On the FPGA side, though, you can access the AUX I/O ports as an FPGA resource, and would probably be able to accomplish something along the lines of PWM, but there aren't any examples showing anything like this. I'm also not sure what kind of update rates you could realistically achieve.
If you wanted to dig into this more it'd be best to make a new thread dedicated to this topic. This initial thread is over a year old and not really discussing this topic.
Regards,
Cason
NI Applications Engr.
Cassandra Longley
Senior Technical Support Engineer - FlexRIO, High Speed Serial and VRTS
