Re: [Discuss-gnuradio] QT Vector Sink Issue

[Nigel Steed]

Hi Martin,

In my application I am generating a vector of amplitude values (of length 128) 
obtained at different frequencies. My flowgraph contains an OOT Block which is 
stepping the SDR and saving an amplitude value for each frequency, generating 
an output sample for each frequency at a time. I then convert this stream to a 
vector using StreamToVector and display using the vector sink which never 
updates the data, only the vertical axis.  If I put a time sink directly after 
my OOT Block with the number of points set to the vector size, that works ok. 
My issue is I need to anotate the plot axis as frequency points, which you can 
freely do with the vector sink but not the time sink.

Maybe I need to reconfigure my OOT module to output a vector of length 128, 
rather than streaming out 128 samples ?

Thanks,

Nigel 

-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Martin Braun
Sent: Wednesday, February 24, 2016 10:25 PM
To: address@hidden
Subject: Re: [Discuss-gnuradio] QT Vector Sink Issue

Just to make sure we're all on the same page: The vector sink is meant to 
display vectors of data, one at a time. It's basically like the frequency sink 
if you had to vectorize and FFT the data yourself.

So putting a time signal into the vector sink is maybe not the right thing to 
do, but I'm not sure what your application is exactly. There are some examples 
for the vector sink, maybe they help you understand the issues better.

The vector sink always draws a line at 0, and another at the ref level.
I'm not sure why it draws the line at 0, tbh. Who wrote this damn... oh it was 
me. Still, not sure why it's there.

Cheers,
Martin

On 02/24/2016 04:39 AM, Nigel Steed wrote:
> Hi All,
> 
>  
> 
> I am currently trying to compare any difference between the QT Time 
> Sink and the QT Vector Sink code. I have a GRC Flowgraph which uses 
> both of these plots. The QT Time Sink works every time, but if I 
> connect a QT Vector Sink at the same point it fails to display data 
> other than zero, although the axis updates as auto range is enabled.
> 
>  
> 
> The data feeding the sinks has been decimated down to a slow rate to 
> provide a vector every second. The time sink works updating every 
> second, but the only update on the vector sink is the axis adjusting, 
> and the data remaining at zero.
> 
>  
> 
> If I simplify the flowgraph to a source, stream to vector and then 
> vector sink it all works fine.
> 
>  
> 
> I am assuming the GNURadio scheduler must be coping with this setup as 
> the axis on the vector plot update at the right rate, but the data 
> line is fixed at zero.
> 
>  
> 
> Has anyone else seen this behavior ? I am using version V3.7.9.1.
> 
>  
> 
> Kind regards,
> 
>  
> 
> Nigel
> 
>  
> 
> 
> 
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> 


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