On Tue, Mar 24, 2009 at 04:03:36PM -0300, Ronaldo Nunez wrote: > Hi folks, > > I tried to TX a FM modulated signal using USRP2 BasicTX. > The signal was a 440 Hz sinusoid, and the carrier 1 MHz. > I used the signal generator and fm modulator blocks provided by GNURadio. > > When I tx it the follow message appeared on the screen: > > USRP2::Tx_RAW: FIXME: short packet: 1 item (32 bytes) > > Sometimes the item number changes to 4 or 8... > What that mean? > > I took a look at the usrp2_impl.cc (last revision) and i couldn't > identify any problem... > > Any suggestion is welcome. > Regards, > > Ronaldo
Hi Ronaldo, There's a bug in the on-the-wire format for the USRP2 where we're not currently transmitting the valid length of the packet. With ethernet, the minimum packet size is 64-bytes, and there are some times where the host code is naively fragmenting the received samples in a way that produces a packet that is too short for ethernet. I've opened ticket:378 on this. It will be properly fixed when we rework the on-the-wire format as part of the VRT work, but I think there's an intermediate step that can avoid most cases of the problem happening. I'm not sure that I can find time to fix this in time for 3.2.0, but if you'd like to take a look at it, we'd love a patch for it. What needs to happen is that the loop in usrp2_impl.cc(tx_raw) that fragments the nitems items needs to be a little smarter about breaking the items into ethernet frames. Each piece needs to be between 9 and U2_MAX_SAMPLES samples long. (9 works out to the smallest number of samples that plus the headers ends up being >= 64 bytes). Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
