Changes to improve usability about qucs_s HOT 11 CLOSED

Thanks for the feedback! Here is my explanation on proposed improvements.

My biggest gripe is the lack of a proper waveform viewer

I have explained my position here: #352 In principle I am agreed that Qucs-S would benefit from adding a waveform viewer. Also there were plans to redesign the plotting system using Qwt toolkit. But it's need to assign a full time developer for this task. It is not a weekend project. Currently Qucs-S has no full time developers. So, don't expect the waveform viewer to be implemented in the next years.

The lack of customizable keyboard shortcuts really hurts usability.

There exists unfinished shortcut manager for Qucs Qucs/qucs#558 It's need to evaluate its status.

The wire tool is very finicky.

This may require redesign of the custom widget representing schematic. Again full time developer needed.

When you zoom with the mouse, In Qucs, it is the top left corner.

I cannot reproduce this. The zooming area is centered around the mouse pointer. We have added some new zooming modes in the recent update.

There are too many voltage symbols for voltage sources.

I don't agree with this. The different sources are more convenient in my opinion. You may use unified SPICE source if required. Regarding the TD parameter for Sine source, I can add it in the next update.

In qucs, you have to write an equation, such as db(V(out)/V(in))

The equations approach was proposed by the previous developers team. I am making some steps in order to get rid of equations like dB. I have added a possibility to define dB scale for Y-axis:

Furthermore, there's no easy way to do FFT.

Please explain what do you mean. I have added a spectrum simulation already in 0.0.24 See #88 What a more easier way to define FFT do you mean? I can add an automatic generation of the dB spectrum for existing simulation.

In LTSpice, you simply click on the code and that's it.

Yes, this would be a great improvement. But see my comment that there are no full time developers in the project now.

Saving transistor parameters by default.

I will look what could be done here without a need of the deep redesign.

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I cannot reproduce this. The zooming area is centered around the mouse pointer. We have added some new zooming modes in the recent update.

Thanks for your reply. Here's how zooming works with the mouse on my end. All I'm doing is holding down control and using my mouse wheel.

Here's how I expect it to work. This is from LTSpice.

I don't agree with this. The different sources are more convenient in my opinion. You may use unified SPICE source if required. Regarding the TD parameter for Sine source, I can add it in the next update.

In LTSpice, you can change a source without having to change the symbol. How is this less convenient?

Presently if I want to apply a signal to a node, I need to use a DC Voltage and an AC voltage because the AC voltage does not have an offset parameter. Also, the name "AC voltage" is very confusing because AC voltage means, in most of the software I've used, the voltage you apply during AC analysis. Incredibly, there are two AC Voltage sources to make it even more confusing. Why not call the one used in transient as "Sine Source" and the one used in AC as "AC source". The unified SPICE source is nice to have only if you can have a GUI interface that does not require the user to remember the SPICE syntax.

Please explain what do you mean. I have added a spectrum simulation already in 0.0.24 See #88 What a more easier way to define FFT do you mean? I can add an automatic generation of the dB spectrum for existing simulation.

Last time I tried to do FFT, I search this forum and the way that was recommended was to use raw ngspice code where I inform ngspice to do FFT, which I found a bit inconvenient.

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1. whell zoom to mouse pointer is issue - yes
2. diagram zooming and markers is two different tasks. zooming planned to next release. markers TBD
3. ability to create a RC circuit in 10 seconds is not killer feature for me. but we will think about how to improve the process of creating circuits.

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3. ability to create a RC circuit in 10 seconds is not killer feature for me. but we will think about how to improve the process of creating circuits.

The point I was making is that it is much faster to get components in LTSpice.

In qucs-s, you have to move your mouse from the schematic area to the components tab, down the components search bar, search, then move your mouse all the way to select the component. It's a very slow process if you have to repeat it many times for other components.

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I suggest next shotcuts combination
C (open components panel and focus on search textbox) + "cap" + ENTER
L (open library panel and focus on search textbox) + "nmos4" + ENTER

another options for quick reuse elements is "favorites" or (and) "last used" component lists

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Here's how zooming works with the mouse on my end.

Yes, I understood now. The zooming doesn't follow the mouse pointer on sequential zoom. Don't expect a quick fix here, because the legacy code may be responsible for this.

In LTSpice, you can change a source without having to change the symbol.

The redesign of the existing sources and designing new ones is not considered. But I can add VO and TD parameters for the sine source. The sources were designed to provide compatibility across Qucsator/SPICE and this compatibility should be preserved. Qucsator still have many unique features for RF simulation and we are intending to still maintain it.

there are two AC Voltage sources to make it even more confusing

The red devices should be used only if you need additional SPICE parameters. The blue unified devices are sufficient for the most of cases.

The point I was making is that it is much faster to get components in LTSpice.

The starting point should be to evaluate the existing shortcut manager status Qucs/qucs#558 I would put this task as a low priority.

Last time I tried to do FFT, I search this forum and the way that was recommended was to use raw ngspice code

This approach is totally outdated. You should use a new simulation type (Spectrum analysis) for FFT. Sorry, but the documentation update was delayed. Writing the documentation requires much more time effort than writing the code.

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I have added the VO and TD parameters for sine source by the recent commit on the current branch. The new parameters will be available since the next release.

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@ra3xdh, just merged the changes. I tried it and got this V4 in 0 DC 0.354 SIN(0.354 0.5M 1K 0 0 0) AC 0.5M ACPHASE 0. Why are you setting the ac voltage the same as the transient voltage?

There is DC voltage for DC simulation, transient voltage for transient simulation, and ac voltage for ac simulation. If you use the same transient voltage as the AC voltage, you will always have to divide every node in the circuit with respect to this transient voltage to get the correct result. To avoid this, you set the ac voltage to 1.

I think this is why I was confused by the fact that there are more than one ac voltage source. I though the red one was supposed to be the one you use for ac simulations. This is very confusing and can give someone the wrong impression about the performance of the circuit. Say I had chosen the transient voltage to be 0.5m. Let's say I measure the gain at some point in the circuit using db(V(node)), then the gain that I will get will be 3dB more than reality.

Here, you can see LTSpice distinguishes between the transient and the ac voltage.

This is also cadence virtuoso:

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Why are you setting the ac voltage the same as the transient voltage?

Everything is correct. It is done to provide compatibility across Qucsator/SPICE. Qucs application never used separate setting for AC and TRAN voltage. Look at legacy schematics. This setting will not be reconsidered.

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Here is the outcome of the discussion:

• The adding waveform viewer or waveform probe may be useful, but not possible in the near future. This task requires full time developer to be assigned and cannot be performed in the current time
• The adding LTspice style voltage sources is not considered. The backward compatibility should be priority. I have added some SPICE parameters to AC source.
• The FFT analysis was added long time ago #88 Need to update the documentation
• Shortcut manager may be added as a low priority task. See #368 You may track the status here
• The solution for save support provided in #357 See my examples in comment.

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@ra3xdh, if the transient voltage is the same as the ac voltage, does that mean that every time I do ac analysis and I want to know the voltage at some node out, I need to create an equation db(V(out) / V(in)), where in is the node where the voltage source is connected?

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