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Re: [Discuss-gnuradio] Problems with 2 RX

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] Problems with 2 RX
Date: Wed, 9 May 2007 09:41:07 -0700
User-agent: Mutt/1.5.9i

On Wed, May 09, 2007 at 09:27:11AM -0700, Dan Halperin wrote:
> Eric Blossom wrote:
> > On Wed, May 09, 2007 at 01:02:52PM +0200, Albert Rodriguez wrote:
> >> We're trying to receive two signals from two different RFX2400 in the
> >> same USRP. We've already read everything about setting the rx mux and
> <snip>
> > These lines:
> > 
> >>    r=src.tune(0,subdev1,freq)
> >>    r=src.tune(0,subdev2,freq)
> > 
> > Should be:
> > 
> >>    r=src.tune(0,subdev1,freq)
> >>    r=src.tune(1,subdev2,freq)
> > 
> > BTW, checking the return value is always a good idea ;)
> Can you explain this? I was under the impression that the first
> parameter to tune was which USRP board, and they're using the same USRP.

The first parameter to the CONSTRUCTOR is the USRP board.
In the call to tune, the first parameter is the channel that we want
to tune (in the code below from usrp.py, u is effectively self.  Ignore it.)

def tune(u, chan, subdev, target_freq):
    Set the center frequency we're interested in.

    @param u: instance of usrp.source_* or usrp.sink_*
    @param chan: DDC/DUC channel
    @type  chan: int
    @param subdev: daughterboard subdevice
    @param target_freq: frequency in Hz
    @returns False if failure else tune_result
    Tuning is a two step process.  First we ask the front-end to
    tune as close to the desired frequency as it can.  Then we use
    the result of that operation and our target_frequency to
    determine the value for the digital down converter.

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