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Re: [Discuss-gnuradio] Using USRP from multiple applications simultaneou

From: John Gilmore
Subject: Re: [Discuss-gnuradio] Using USRP from multiple applications simultaneously
Date: Sun, 01 May 2005 15:02:40 -0700

The current software was designed to let you run one transmit
application and one receive application at the same time.  If that
doesn't work, please report exactly what happens when you try.

Yes, that's not optimal in a 4-daughterboard, 8-antenna system, but
it's what we have right now.  The problem is that because of the USB
interface chip, they all have to share a single USB endpoint back to
the host.  Our hardware isn't smart about how to share the bandwidth
among various applications.  The FPGA's "mux" lets us move one or more
channels in each direction, but due to FPGA programming and buffering
limitations, they all have to be using the same data rate over the USB

Whatever more-complicated muxing we may come up with to allow
arbitrary settings on different daughterboards will almost certainly
blow the "zero copying" model you guys are prematurely optimizing.
SOMEBODY in the library or kernel will have to tease those data
streams apart so the separate applications can access them without
interfering with each other.

So glad you brought both topics up together...  :-)


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