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[Discuss-gnuradio] About signal triggering

From: Wu Ting
Subject: [Discuss-gnuradio] About signal triggering
Date: Mon, 13 Feb 2012 10:58:08 +0900

Hi all,


I’m now using USRP N200 with LFRX daughterboard.


I’m trying to detect radio signals produced by lightning discharges. When lightning does not occur, the system just detect the signal but does not record data. When lightning happens, it triggers the system and the system starts to write data into a file.


Each triggered record comprises pre-trigger part and post-trigger part. For example, if lightning triggers the system at time 0, the triggered record should starts from time -100 ms to 900 ms. In other word, the system has to record some part of data before the trigger point.


I’m now using GNURadio to construct the software, but I’m really new to it. I’ve been working on it for two weeks. I’m now using vector_sink_x to store signal of each second, find the maximum of the vector and compare it with the trigger point, and if the maximum value is larger than the trigger point, use file_sink to record the data. However, this process seems to be slow.


One of my colleagues told me that usually such system provides pre-defined function for recording triggered signal, and the function can control pre-trigger time. But so far I have not found any related function or module. Does anyone know what function or module may be useful, or any example that may be similar, or any idea for recording triggered data?


Thanks in advance.



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