Re: [Discuss-gnuradio] Dynamically changing parameters of a block

[kaleem ahmad]

Hi Eric,

Two nodes, each consists of one USRP and an RFX2400, are involved, one as a
Master(Transmit ... receive echoed version...Transmit new packet and so on)
and the other USRP is Slave (Receive...echo back the received packet). I am
creating 1 usrp source (for transmitting) and 1 usrp sink (for receiving)
for each node. 

I dont understand "You should be creating 1 each for each USRP and keep them
open the
entire time."

How can I keep both source and sink open all the time without using
disconnect/disconnect_all. Because when I am transmitting my source is a
file and my sink is usrp. At same USRP node when I am receiving my source is
usrp and my sink is a file. My problem is how can I construct a graph which
either keep both of these things open at a time or dynamically connect and
disconnect them.

Can you suggest me an example flow graph, or e.g can you comment that
something like following is correct way to handle it:

+++++++++++++++++++++++++++++
while(1):
       send()
       receive()
       delay(500ms)
---------------------------------------
send(fg):
     fg.connect(file_source, frammer, NRZ, modulation, gain, usrp)
-----------------------------------------
receive(fg):
     fg.disconnect_all()
     fg.connect(usrp, filter, de_modulation, correlation, file_sink)
     wait_for_timeout()
     fg.disconnect_all()
++++++++++++++++++++++++++++++++++++++++++

It is just an example flowgraph and soesnt matter if the correct blocks are
used, but the thing which I want to know is the order of connect() and
disconnect_all(), is it possible to have like this and will it work with
such delays.

Best Regards

Kaleem Ahmad

Eric Blossom wrote:
> 
> On Tue, Sep 30, 2008 at 02:09:47AM -0700, kaleem ahmad wrote:
>> 
>> Any suggestions!!!!!!!!!!!!!!!
> 
> How many usrps are involved in this?
> How many usrp sinks and sources are you creating?
> You should be creating 1 each for each USRP and keep them open the
> entire time. 
> 
> Eric
> 
> 
>> kaleem ahmad wrote:
>> > 
>> > Hi Eric and others,
>> > 
>> > I also have a similar problem, but it is not limited to 'gain control',
>> > Actually I want to implement an echo back or ping pong transmission
>> > system.
>> > 
>> > 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() method 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...
>> > 
>> > Is it possible and is there any example code which doing something like
>> > this or otherwise can you please suggest me some way to do this.
>> > 
>> > Thanks
>> > 
> 
> 
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> 
> 

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