[Discuss-gnuradio] how to set parameters for usrp_nbfm_ptt.py

[zhifeng chen]

Hi,
I just buy two sets of RFX900 a few days ago. now I can run usrp_siggen.py and usrp_fft.py normally now. But when I try to run usrp_nbfm_ptt.py for a full duplex test, I can hear nothing in both sides. I check the source code and find 
self.set_transmit(False) in the __init__ of ptt_graph, so I change it to self.set_transmit(True) in PC_A with microphone input and leave it False in PC_B with speaker output. Now there are some noise output in PC_B, but still don't have any voice ouput come from my input from microphone in PC_A. I am try to search in archives of this maillist and read the source codes by myself, but still have not find the answer. Could anyone help me for below question:
1. Do I need to change the usrp_nbfm_ptt source code to test RFX900? If so, how to change for simplex and duplex respectively?
2. I see rx_subdev_spec, tx_subdev_spec, audio_input and audio_output options may be detect by program automtically if we don'e spectify, is it right? I also find side A seems to be first priority if automatically detected, but why there are still signal input and output in side B at the same time?
3. How to set parameters in command line to run usrp_nbfm_ptt.py, my current setting is: ./usrp_nbfm_ptt.py -f 900e6 for both PC_A and PC_B.
4. after showup the gui, I can't move the sliders in the control panel, although there are sliders there. Is it normal?

Thank you very much!

Sincerely,
Zhifeng