Re: [Discuss-gnuradio] USRP Basics questions

[Josh Blum]

You want to probe the SMA connectors. The pins tx0-tx7 are digital 
control lines. If you see any signal on the control lines, it is 
probably very weak leakage from the DAC.

Somya Ajmera wrote:
> Hi Josh, on the  SMA connectors I had connected my transmit receive antennas. I 
> wanted to know if while transmitting and receiving signals using USRP sink and 
> source blocks, can I silmatenously probe any pin on the transmit/receive 
> daughter board inorder to see the signal out and in to USRP. Also I was trying 
> to make an OFDM system by implementing the following blocks:
>
> Random Source:---->OFDM Modulator:------------>USRP Sink
> [Minimum=0;                [ Modulation:8 QAM               [Unit Number=0
> Maximum=2;                 FFT Length=512                   Interpolation=400
> Num Samples=1M        Occupied tones: 200           Frequency=100M
> Repeat=Yes]                 CP Length: 128                    Gain=0
>                                       Pad for USRP=Yes              Side=Side A]
>                                       Payload length=0]
>
> After running this, when I probed pin tx0 - tx7 on the daughter board, I was 
> able to see some waveforms on the scope. But when I build the receiver system:
>
> USRP Source:----------->OFDM DeModulator:------------>FFT Sink
>
> [Unit Number=0                [ Modulation:8 QAM               
>
> Decimation=400                FFT Length=512                   
>
>  Frequency=100M              Occupied tones: 200          
>
> Gain=0                                CP Length: 128                    
>
> Side=Side A                                                   
>
> RX Antenna=RXA ]                                    
>
> I am get the following warning:
> "** (python:4085): WARNING **: IPP request failed with status 1030
>        Timeout "

You can ignore this, its just wxpython molesting your printers.

> and now if i probe the same pins on the daughter board, I am not able to see 
> any waveforms. Can you please help me to figure out this behaviour.
>
> Thanks & Rgards,
> Somya Ajmera