Re: [Discuss-gnuradio] Transmission time control from python level

[Nazmul Islam]

Hi Josh,

Thanks a lot for your reply. Can I control the TX stream from the GRC generated python code? In other words, can I change the UHD:USRP source/sink parameters to set up the time stamps or controlling the scheduling?

Thanks,

Nazmul

On Sun, Jul 8, 2012 at 12:30 AM, Josh Blum <address@hidden> wrote:

On 07/07/2012 09:30 AM, Nazmul Islam wrote:
> I have three USRP's and I want them to transmit a continuous stream of
> repeated GLFSR source in non-overlapping manner. In other words, each
> transmitter will transmit the source for 1 second and then pause for 5
> seconds. All transmitters will transmit during the 'odd' seconds so that
> there is a 1 second gap between the sources. This process should continue
> for ever.
>
> Currently, I am controlling the starting and stopping time of the flow
> graphs to achieve my goals. Unfortunately, the code/flowgraph sometimes
> hangs after 15-20 starts. I am using the following code:
>
> ............
> tb = GLFSR_transmitter()   # The Tx flowgraph : GLFSR source (float) -->
> RRC filter --> USRP Sink
>
> var = 1
>
> while var == 1:     # This process should run forever
>
>      time.sleep(1-time.time() + int(time.time()))
>
>      condition = ((int(time.time())%6) == 0)       # The transmitter will
> transmit after every 6 seconds
>
>      if (condition):
>
>           print time.time()
>
>           tb.start()
>
>           sleep(1)      # The transmitter runs for 1 second
>
>           tb.stop()
>
>           tb.wait()
> ............................
>

You really dont want to stop and start the flow graph. TX streams can be
controlled with stream tags. Links to header docs and example here:
http://code.ettus.com/redmine/ettus/projects/uhd/wiki/GNU_Radio_UHD#Using-UHD-with-GNU-Radio

> My USRP's don't seem to like this frequent starting and stopping of flow
> graphs, especially when I am transmitting at 15-20 MS/s rate. I am using
> USRP N210 (SBX daughterboards) and the latest gnuradio images. What other
> things can I do to achieve this timing control? I am looking for options in
> python level since my C++ OOP background is not strong. Josh talked about
> some python based blocks (

> ttps://github.com/guruofquality/gnuradio/tree/python_blocks2<https://github.com/guruofquality/gnuradio/tree/python_blocks2>)

> in (http://old.nabble.com/How-to-implement-a-TDMA-system-td33727749.html).
> They seem to be merged to the master (
> http://gnuradio.org/redmine/projects/gnuradio/repository/revisions/f8581fb475267e1a97eaab962e423559fb4bfce2)
> but I can't find the blocks.
>

All that stuff + instructions and coding guide can be found here
https://github.com/guruofquality/grextras/wiki

-josh

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-- 
Muhammad Nazmul Islam

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