Johnathan,

Thanks for the speedy response.

Is there any way I could use one USRP to both transmit and receive a
signal?  That is, I want to use benchmark_tx.py to send out a dbpsk
modulated signal and use benchmark_rx.py to receive this same signal.  Would
this be possible?  I'm using a FLEX400 daughterboard.  I actually have two
of them.

Thanks,
Jeffrey

On 8/9/07, Johnathan Corgan <[EMAIL PROTECTED]> wrote:
>
> Jeffrey Ung wrote:
>
> > I installed GNU Radio on an Intel OSX machine (with the help of
> > Michael Dickens (THANKS!)) and now I was wondering if it were
> > possible to specify which USB port the computer should use when
> > looking for the USRP.  I ask because I want to connect two USRPs to
> > the same computer and run on as a TX for dbpsk and the other as a RX
> > for dbpsk.  Is this even possible?  If so, how would I go about it?
>
> It is possible to plug two USRPs in to the USB.
>
> If you are writing your own software, you'll need to add the 'which'
> parameter to usrp.source_c() and usrp.sink_c():
>
> src1 = usrp.source_c(which=0)
> src2 = usrp.source_c(which=1)
>
> Unfortunately, many of the example programs are written to assume there
> is only one USRP, including the digital 'tunnel' program.  So you'll
> need to modify these to accept a new command line parameter.
>
> Now which USRP gets assigned #0 and #1 is dependent on the order they
> enumerate on the USB, first by bus, then by device.  This may be
> affected by which one is plugged in first or turned on first.
>
> It's possible, when writing your own code, to retrieve the serial number
> from the source_c object and use that to determine which actual hardware
> unit you've grabbed.
>
> The other caveat is that most motherboards share a single USB controller
> for all their ports.  So you're sharing the same 32 MB/s bandwidth
> across two USRPs now, effectively halving the maximum RF bandwidth you
> can work with if both USRPs are using the USB equally.
>
> --
> Johnathan Corgan
> Corgan Enterprises LLC
> http://corganenterprises.com
>
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