Re: [Discuss-gnuradio] How to dynamically stop the host PC receiving samples from USRP and restart it again without touching the top block?

[Josh Blum]

On 06/01/2012 10:07 AM, Alex Zhang wrote:
> Hello Josh,
> 
> I am testing this solution. But before I get the result, just want to make
> sure:
> Does the stream command STREAM_MODE_STOP_CONTINUOUS stop the incoming
> packets from the USRP to PC, or just stop the flow graph to receive the
> packets from USRP while the packets are still coming into the PC thru the
> ethernet between USRP and PC?
> 

Yup, the usrp->stop() calls STREAM_MODE_STOP_CONTINUOUS, which actually
stops the flow of packets from USRP to host.

-josh

> On Thu, May 31, 2012 at 1:28 PM, Josh Blum <address@hidden> wrote:
> 
>>
>>
>> On 05/30/2012 06:33 PM, Alex Zhang wrote:
>>> Hi,
>>>
>>> In my applications, after the flow graph is initialized, I need to
>>> dynamically control the receiving of the USRP samples, i.e, at time T1, I
>>> want the USRP to transfer the received samples to PC, while in T2, I do
>> not
>>> allow the PC to receive these samples.
>>> Stop receiving the unusing packets from USRP can save the traffic over
>>> ethernet and decrease the demands of processing resource on host PC.
>>>
>>> the gr_mute block seems only suppress the incoming packets to further
>>> processing, but these unusing samples can still come into the flow graph.
>>>
>>> Also, the tb.run and tb.wait can be executed more than twice as wish, but
>>> it seems to be not so flexible. It would be good if there some commands
>>> called to control the block of uhd.usrp_source to achieve such purpose?
>>>
>>>
>>
>>
>> I had a post on this recently, wish I could find it in the archives...
>>
>> So, the problem with stopping streaming is that the work function will
>> return zero and the scheduler marks the block as done.
>>
>> So, if you take this changeset here. You should be able to stop and
>> restart a running USRP without problem.
>> http://gnuradio.org/cgit/jblum.git/log/?h=wip_uhd_stopper
>>
>> Use the following methods on the block:
>>
>> usrp->start()
>> usrp->stop()
>> and if you want to be precise about time, call
>> usrp->set_stream_time(...) before calling start()
>>
>> -josh
>>
>>>
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> 
>