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From: | Sean Nowlan |
Subject: | Re: [Discuss-gnuradio] Async Messages for Tx Timestamps |
Date: | Mon, 8 Apr 2013 19:19:51 -0400 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130329 Thunderbird/17.0.5 |
On 04/08/2013 04:45 PM, Jordan Otomo wrote:
I'm a bit confused by what you mean when you say you're transmitting continuously in a packet-based application. Are the packets back-to-back in your sample stream? Or are you stuffing a bunch of zero samples in between packets? That isn't the cleanest way to do it. It would be better to use start-of-burst ("tx_sob") and end-of-burst ("tx_eob") tags if you're using gnuradio.Hi, I have a packet-based application where it would be useful to know exactly when each packet has been successfully radiated by the USRP (N200). It seems that UHD and gr-uhd already provide similar functionality for receiving asynchronous messages when a burst has been successfully transmitted (EVENT_CODE_BURST_ACK). However, in my application, I'm transmitting continuously and don't use end_of_burst tags. Would it be possible for the USRP to post messages to the event queue when it has transmitted a sample with a generic tag attached? If not, will I experience an interruption of my signal or any latency if I insert end_of_burst tags into my continuous stream of samples? Your advice is greatly appreciated.
Gnuradio end-of-burst tags will signal UHD firmware to bring down the TX chain. The tag gets converted into a flag in a metadata struct. This struct is sent with an 1-sample buffer of samples when send(...) is called in gr_uhd_usrp_sink. (See line 376 and thereabouts here: http://gnuradio.org/cgit/gnuradio.git/tree/gr-uhd/lib/gr_uhd_usrp_sink.cc).
Thanks! Jordan _______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Hope this helps! --sean
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