Feeding multiple traces to scope

[srcejon]

Hi,

I'm trying to use the scope to help debug a demodulator. This is pretty good at displaying two signals from the demod, but it would be helpful if it could display more than 2 simultaneously (I've set up 15 different signals to probe, but not all need to be visible simultaneously).

Currently, I have combo boxes that select the different signals to send to the scope on the real and imag parts of the input. I've tried embedding two scopes, for 4 signals, but the triggering isn't synchronised, and so they get out of sync (unless only start/stop acquisition is used)

It seems the scope can display more than 2 traces in the waveform display, but these only come from one IQ input, as far as I can see? Is there a way to support more input channels?

This is perhaps similar to #16

[f4exb]

Yes similar but not exactly the same. #16 is for a channel analyzer that would accept a MIMO (MI that is) baseband thus being fed by multiple synchronous I/Q streams. Of course to make it really useful one would have to be able to combine traces from different inputs in the scope. So in fact this one would be a prerequisite for #16

[f4exb]

The scope component being rather sensitive and brittle I'd rather make it a new multiscope component possibly carrying out some redesign. The scope is one of the oldest components and has probably accumulated a good amount of technical debt.

[f4exb]

For the scope part this is to be covered by #898

[f4exb]

See https://github.com/f4exb/sdrangel/releases/tag/v6.14.0 for details

[srcejon]

Great, thanks. Will give it a try.

[srcejon]

Just giving this a try.

During initialisation, I call:

m_scopeSink->setNbStreams(2);

Then in the channel in sampleToScope(), I have:

    Real r = std::real(sample) * SDR_RX_SCALEF;
    Real i = std::imag(sample) * SDR_RX_SCALEF;
    SampleVector m_sampleBuffer1;
    SampleVector m_sampleBuffer2;
    m_sampleBuffer1.push_back(Sample(r, i));                    
    m_sampleBuffer2.push_back(Sample(r, i));
    std::vector<SampleVector::const_iterator> vbegin;
    vbegin.push_back(m_sampleBuffer1.begin());
    vbegin.push_back(m_sampleBuffer2.begin());
    m_scopeSink->feed(vbegin, m_sampleBuffer1.end() - m_sampleBuffer1.begin());
    m_sampleBuffer1.clear();        
    m_sampleBuffer2.clear();  

But this results in a "vector subscript out of range" exception in:

with streamIndex=1

Is there something else I need to add / change?

[f4exb]

This should work. From the screenshot it seems initialization is not complete when setNbStreams is invoked. There should be 50 items on the second cell as well.

Edit: this loop https://github.com/f4exb/sdrangel/blob/master/sdrbase/dsp/scopevis.h#L610 is missing in setNbStreams

[srcejon]

Thanks - it no longer crashes.

However, I only see 0 in the "trace stream source" combo box. How should this be initialised? It would obviously be nice to initialise it with names corresponding to what each stream is.

Looking through glscopegui.cpp, I can't see anything that adds items to ui->traceStream, and Ui::GLScopeGUI* ui; is private, so I don't know how to access it from the ChannelGUI to add items. (E.g. ui->scopeGUI->ui->traceStream->addItem("Therehsold"); doesn't compiler)

[f4exb]

There is very little room in the combo and certainly not enough for more that a few characters. So having a relatively long word here like "Threshold" is a bad idea.

Yes Ui::GLScopeGUI* ui; is private, this is normal because it should be handled by GLScopeGUI exclusively. I think however that it is missing methods around ui->traceStream to effectively handle multiple traces.

[f4exb]

Two new methods in GLScopeGUI:

• void setNbStreams(unsigned int nbStreams);: sets the number of streams with default names (index numbers)
• void setStreams(const QStringList& streamNames);: sets the stream names from a list of strings. Thus the number of strings sets the number of streams.

[srcejon]

I'm not sure if you missed the comments in PR #939, but as you didn't reopen the bug, I thought I'd mention it again. It seems multiple streams do not work for the Radio Clock plugin. I just see 0s on the scope. (A single stream is fine).

[srcejon]

I can now select the different streams for X trace, thanks.

However, it doesn't appear to work for Y. If I add a Y trace, I seem to get the same data on Y as X, regardless of the stream selection.

E.g. I have TH selected here - but the Y trace is showing the MagSq signal.