Re: [Discuss-gnuradio] Scheduling a block even with no input items RE: Flow graph blocking when doing 2x1 transmission

[David Halls]

Hey Martin,

Good to hear from you as always. Gnuradio scheduling baffles me more than anything else on this planet. The day I get my head around it will be a happy day indeed. :0

The problem with using 'sob', 'eob' is because I have two inputs to the USRP UHD sink. One is constantly transmitting and has items coming in from time=0, but the other has no input items from time=0, they only arrive later on. As a result the sink seems to block waiting for items on *both* inputs before it will transmit anything. I don't want the USRP to have to wait for the second stream to be populated before it transmits anything...

I thought 'forecast' may help me out, but wasn't sure what to put in the function to make it schedule even when there are no input items?

David

-----Original Message-----
From: Martin Braun [mailto:address@hidden
Sent: 03 June 2014 14:53
To: David Halls; address@hidden
Subject: Re: [Discuss-gnuradio] Scheduling a block even with no input items RE: Flow graph blocking when doing 2x1 transmission

On 06/03/2014 03:30 PM, David Halls wrote:
> Dear All,
>
> Had anyone tried to implementing a gnuradio block that will output
> zeros if there are no items at the input, and will simply copy the
> input to output otherwise?
>
> I find that if there are no items at the input, the block never gets
> scheduled.
>
> I want this block to feed zeros to my USRP until actual data is ready
> to be passed to it.

Hey David,

any reason you can't use eob/sob?

Also, did you set forecast accordingly?

Note that this can go wrong easily: If this blocks produces a bajillion zeros very quickly, nothing will happen until the USRP has consumed them all.

M


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