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Re: [Discuss-gnuradio] Dynamic flow graph control

From: sreeraj r
Subject: Re: [Discuss-gnuradio] Dynamic flow graph control
Date: Tue, 7 Aug 2012 00:39:29 +0800 (SGT)

This might be happening because "gr.file_sink" is not closing the passed file handle until its destructed. I checked "gr_file_sink_base"'s source and various functions like open, close and unbuffered writes are supported. Try playing around with these(I haven't used these things yet).

http://www.reynwar.net/gnuradio/sphinx/gr/sink_blk.html (Check gr.file_sink section)
Sreeraj Rajendran

From: Nazmul Islam <address@hidden>
To: GNURadio Discussion List <address@hidden>
Sent: Monday, 6 August 2012 8:52 PM
Subject: Re: [Discuss-gnuradio] Dynamic flow graph control


I am trying to simplify my previous email for clarification. I am looking to resolve the following issue:

I have two flowgraphs:

1. USRP Source --> File Sink     #   self.file_sink = gr.file_sink(gr.sizeof_gr_complex*1, "Data.dat")
2. USRP Source --> Null Sink

I have defined both of them inside a class. I use unlock --> disconnect --> connect --> lock to switch from one flow graph to the other. When I connect USRP-->Null, I work on the stored data of "Data.dat" file. Thereafter, I want to clear the data of the "Data.dat" file. I use the following line of code to obtain my goal:


However, this command does not seem to erase the data of "Data.dat" file, i.e., when I run flow graph 1 again, the previous file does not get erased. The file size of "Data.dat" keeps growing with each run of flow graph.

How can I erase the contents of the file sink before I switch to flow graph #1?

Any suggestion will be very appreciated. Sorry for sending two emails on the same matter.



On Sun, Aug 5, 2012 at 6:46 PM, Nazmul Islam <address@hidden> wrote:

I have an application where I need to collect the data for 5 seconds from the USRP source and do offline processing for 5 seconds in a repeated manner. I am planning to use the lock & unlock features of the gnuradio to obtain my goals. The major part of my code is given below:

class SingleSource(grc_wxgui.top_block_gui):

self.source = .....                                                                            # Source block
self.throttle = ......                                                                           # throttle
self.file_sink = gr.file_sink(gr.sizeof_gr_complex*1, "Data.dat")            # File Sink
self.null_sink = ............                                                                   # Null sink

self.connect((self.source, 0), (self.throttle, 0))                                     
self.connect((self.throttle, 0), (self.sink, 0))

 def reconf1(self):
                self.disconnect((self.gr_throttle_0, 0),(self.gr_file_sink_0, 0))            # Disconnecting the throttle & the file sink
                self.connect((self.gr_throttle_0, 0), (self.gr_null_sink_0, 0))               # re-connecting the throttle & the null sink

 def reconf2(self):
                self.disconnect((self.gr_throttle_0, 0),(self.gr_null_sink_0, 0))             # disconnecting the throttle & the null sink
                self.connect((self.gr_throttle_0, 0),(self.gr_file_sink_0, 0))                 # re-connecting the throttle & the file sink


if __name__ == '__main__':

    tb = SingleSource()
        var = 1
        tb.start()                                                                                   # Flow graph starts
        for loop in range(0,2):
                sleep(5)                                                                     # Collects the data in the file sink
                tb.reconf1()                                                         # Flowgraph gets locked & reconfigured and unlocked
                tb.unlock()                                                         # Now, data is going to the null sink. I don't need this data
                 .................                                                # Offline processing
                open("SineData.dat",'w').close()                       # I WANT TO ERASE THE DATA IN THE FILE SINK AFTER PROCESSING
                                                                                    # SO THAT THE FILE SIZE DOES NOT BIGGER
                tb.reconf2()                                       # File sink is getting reconnected so that I can collect the data in the next run                     

Now, the problem is: the file size of "SineData.dat" should not grow with each loop since I am using open("SineData.dat",'w').close() . In each new loop, I expect the file to only contain the latest information and not the previous ones. However, I am finding that the file size keeps growing with each loop, i.e., the open("SineData.dat",'w').close() command is not working.

Any suggestion will be very appreciated.



Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.

Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.

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