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List:       usrp-users
Subject:    [USRP-users] USRP Source generates more tags than expected
From:       Lukas Haase via USRP-users <usrp-users () lists ! ettus ! com>
Date:       2019-12-16 17:08:08
Message-ID: trinity-88a878c2-c71a-4ced-a774-012a0c505ff1-1576516088747 () 3c-app-gmx-bap63
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Hi,

According to the manual, USRP Source generates tags whenever settings change (e.g. \
center frequency). I would like to use this for my frequency hopping system: A python \
code regularly changes the center frequency of the USRP Source (and Sink) block and \
then I use "rx_freq" tags to detect whenever a switch happened and patch together a \
packet.

I need to convert the sequential data due to hopping to a "parallel" data: For \
example, I hop between three frequencies than after the last frequency, I need to \
process the data for all three frequencies. Hence I need to know when the different \
switch occured.

However, using the "Tag Debug" block I see that for each tune request 6 tags are \
created. For example:

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 14537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 14537796  Source: file_meta_source0     Key: rx_time   Value: {1576453289 \
0.0988063}  Offset: 14537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 15537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 15537796  Source: file_meta_source0     Key: rx_time   Value: {1576453289 \
0.298806}  Offset: 15537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 16537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 16537796  Source: file_meta_source0     Key: rx_time   Value: {1576453289 \
0.498806}  Offset: 16537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 17537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 17537796  Source: file_meta_source0     Key: rx_time   Value: {1576453289 \
0.698806}  Offset: 17537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 18537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 18537796  Source: file_meta_source0     Key: rx_time   Value: {1576453289 \
0.898806}  Offset: 18537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------

----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
  Offset: 19537796  Source: file_meta_source0     Key: rx_freq   Value: 1.85e+09
  Offset: 19537796  Source: file_meta_source0     Key: rx_time   Value: {1576453290 \
0.0988063}  Offset: 19537796  Source: file_meta_source0     Key: rx_rate   Value: \
                5e+06
----------------------------------------------------------------------



I expected only one. Why are there six of them?


Thanks,
Luke





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