I have been working on support of tag handling for the USRP source and
sink blocks in gr-uhd. I will be adding some test and example code, but
if anyone cares to experiment, see my uhd_features branch on jblum.git
http://gnuradio.org/cgit/jblum.git/log/?h=uhd_features
Rather than describe, its easier to paste these excerpts from the docs:
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RX Stream tagging:
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The following tag keys will be produced by the work function:
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- pmt::pmt_string_to_symbol(“rx_time”)
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The timstamp tag value is a pmt tuple of the following:
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(uint64 seconds, and double fractional seconds).
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A timestamp tag is produced at start() and after overflows.
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TX Stream tagging:
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The following tag keys will be consumed by the work function:
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- pmt::pmt_string_to_symbol(“tx_sob”)
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- pmt::pmt_string_to_symbol(“tx_eob”)
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- pmt::pmt_string_to_symbol(“tx_time”)
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The sob and eob (start and end of burst) tag values are pmt booleans.
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When present, burst tags should be set to true (pmt::PMT_T).
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The timstamp tag value is a pmt tuple of the following:
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(uint64 seconds, and double fractional seconds).
-Josh