Re: [Discuss-gnuradio] Packet via USB

[Eric Blossom]

On Tue, Jan 08, 2008 at 04:10:46PM +0100, address@hidden wrote:
> Hi,
> I've observed that all URB allocated in the Tx side are correctly proccesed.
> For example:
> Data -> 25 Byte (from a mpg file)
> Total payload -> 80 Byte (Data + CRC + Padding + Header + ....)
> 
> Total Byte to transfer with a BPSK modulator -> 80 * 8 (bit of a char) * 6
> (sample per symbol) * 4 (Byte - IQ) -> 15360 Byte (multiple of 512 Byte).
> 
> All URB buffers used are multiple of 512.
> In fusb_ephandle_linux::submit_urb (fusb_linux.cc) i have inserted
> wait_for_completion () function from which I get these massages: URB list empy
> (All request).
> 
> I transmit such packets every 1 - 2 seconds (no stream data). But I can't see
> them on the Rx side using usrp_fft.py to observe the signal on the air. I can
> see some signal only occasionally. Is this problem reconducted to the Host PC
> side (maybe the Linux USB driver)?

The tx side seems OK.

usrp_fft doesn't (normally) process all incoming data, since it can't
keep up.  From your description, it looks like you are trying to
detect a very small burst sent once every 1 or 2 seconds. 

Try logging the rx samples to disk using usrp_rx_cfile.py and then
examine the file using octave.

Eric