On TX, if you need your first sample to be valid and everything settled in the radio, you should zero pad ahead of it. If you need your last sample to go out clean, you should zero pad after it. In both cases, a few microseconds worth is usually fine. This flushes buffers and filters, but also gives physical devices like antenna switches to settle.
Matt On Thu, Oct 16, 2014 at 2:46 PM, David Halls <david.ha...@toshiba-trel.com> wrote: > > > -------- Original message -------- > From: Matt Ettus > Date:2014/10/16 22:42 (GMT+00:00) > To: John Malsbury > Cc: David Halls ,GNURadio > Subject: Re: [Discuss-gnuradio] Source Block - Flow Control > > > > On Thu, Oct 16, 2014 at 8:40 AM, John Malsbury < > jmalsbury.perso...@gmail.com> wrote: > >> I'm happy this is working for you, David. So do I understand >> correctly, that the adding tx_time finally made the MIMO case work? >> >> I'd never done burst transmission with multiple USRP outputs. I'm not >> totally surprised but I wasn't sure what would happen. >> >> Maybe someone from Ettus can comment on this? Since UHD is trying to do >> time alignment in the multi_usrp class, what happens to time alignemt in >> the non-continuous-streaming case if you *don't* include a tx_time tag? >> > > > Noncontinuous streaming means there is some amount of down time. If you > don't include tx_time tags, the device doesn't know when to start back up > again, so each antenna is going to start at a different time. > > Matt > > > That seemed exactly the kind of behaviour I saw where sync between the > two streams was lost. Matt, can you comment on whether I need to put dummy > padding items before the first burst? to flush buffers and is there a > delicate way to do this? > > > ------------------------------ > > NOTE: The information in this email and any attachments may be > confidential and/or legally privileged. This message may be read, copied > and used only by the intended recipient. If you are not the intended > recipient, please destroy this message, delete any copies held on your > system and notify the sender immediately. > > Toshiba Research Europe Limited, registered in England and Wales > (2519556). Registered Office 208 Cambridge Science Park, Milton Road, > Cambridge CB4 0GZ, England. Web: www.toshiba.eu/research/trl > > > > ------------------------------ > This email has been scanned for email related threats and delivered safely > by Mimecast. > For more information please visit http://www.mimecast.com > ------------------------------ >
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
