Getting USRP 2 valid IQ values

Here is what I have:
USRP2 + XCVR2450 to receive 2.4 GHz signals. The specs says it’s a 14
bit ADC.

I wrote a simple python block diagram which simply stores the interweave
IQ values to a binary file.

self._u = usrp2.source_16sc(options.interface, options.mac_addr)
self._sink = gr.file_sink(gr.sizeof_short*2, filename)

The program successfully runs, but I don’t see 14 values with two ‘00’
bits attached to I and Q bits. I should see the outputs of the ADC with
appended 0 bits to form 16 bits right? The values of I and Q doesn’t
seem to be correct.

I tried the 32 bit values:

self._u = usrp2.source_32fc(options.interface, options.mac_addr)
self._sink = gr.file_sink(gr.sizeof_gr_complex, filename)

I still see number for and IQ in the e-42 or so. If I do a fft on those
number, it does look like 2.4 GHz and I do see the packet bursts
indicative of 802.11 traffic.

My question is how do I get the 14 bit ADC values out of USRP2?

Thank you for your time.