On Tue, Jun 14, 2011 at 1:22 PM, <r...@ee.ucla.edu> wrote: > Hi, > > I have looked at the python examples tagging where a trigger signal is used > to insert "burst" tags at various stream sample locations. However, what I > would like to do is add a tag at the first sample of a packet. The tag will > be called "send_at_time" and will have a value of time at which to > send. Following questions arise (I am assuming the use of send_pkt() used in > examples in digital): > > 1. Is it possible to tag the first bit? For e.g. can I modify > "message_from_string" called in pkt.py (if I can find the source for it) > msg = gr.message_from_string(pkt,time_to_send) > > 2. If tagging bits is not easy to do, is there some property of stream > samples that indicates "first sample of a packet"? > > Thanks, > Ragh >
Ragh, Yes, the stream tagging system was designed pretty much exactly for this purpose. What you'll need to do is create a new GNU Radio block that looks for the start of packet, and when it finds it, adds a tag to the stream. Have a look at gnuradio-core/src/lib/runtime/qa_block_tags.cc for an idea of how the stream tags work (that is, how to add them to the stream and how to get them). Tom
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