[Discuss-gnuradio] Small point but serious problem for me

[kaleem ahmad]

Hello everyone, 

I posted this question before but never get any response so I am posting it
again because it have become a serious problem for me and I am unable to
solve it. Because of it my entire project is delayed. I have read many posts
which address a similar problem but most of them were in 2006-2007 and I
could not find any clue to solve my problem.

Actually I want to implement an echo back or ping pong transmission system
(This is actually a small or starting part of a big project)

First I implemented two separate transmitt and receive flow graphs in two
separate transmit(), and receive() functions as mentioned in the following: 

Master Transceiver:

      Transmit()            Transmitt one data packet 
      Receive()             Wait in receive for the echoed back packet or
timeout 

Slave Transceiver:

      if (Receive()):             Always wait in receive 
             Transmit()            Transmitt back the received data packet 

But in this method I get an error 'cant open usb device....cant open USRP
0/1'

Then I found flowgraph.disconnect()/disconnect_all() methods and thought
that I should implement a single flowgraph which can dynamically connect
different blocks to transmit and then disconnect and connect with receive
blocks and so on... as follows (my perception):

while (true):
   connect(send blocks)
   disconnect_all()
   connect(receive blocks)
   disconnect_all()

Is it possible (I mean can I do exactly as above, or how can I implement
such a cyclic graph) and is there any example code which doing something
like this or otherwise can you please suggest me some way to do this. 

Please either suggest some solution to 'cant open usb device....cant open
USRP 0/1', or to this cyclic-reconfigurable graph.

Thanks 

Kaleem Ahmad 

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