[Discuss-gnuradio] Dynamic flow graph control

[Nazmul Islam]

Hello,

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.lock()                                                                   
                tb.reconf1()                                                         # Flowgraph gets locked & reconfigured and unlocked
                tb.unlock()                                                         # Now, data is going to the null sink. I don't need this data
                sleep(5)
                 .................                                                # 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.lock()
                tb.reconf2()                                       # File sink is getting reconnected so that I can collect the data in the next run                      
                tb.unlock()

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.

Thanks,

Nazmul


-- 
Muhammad Nazmul Islam

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