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Re: doing math on plots


On Wed, Oct 30, 2019 at 6:42 PM Holger Vogt <holger.vogt@xxxxxxxxxx> wrote:
> The current eeschema-ngspice interface is very limited.

Are there any plans or roadmap for improving it?

> > How would one plot, for example, the difference between two vectors?
> > I tried this in a text box:
> >
> > .save foo=(‘v(/input)-v(/output2)’)
> > .tran 10u 50m
> >
> > but "foo" does not show up in the list of vectors to display in the plot window.
> Here you might have a look at
> https://forum.kicad.info/t/spice-plotting-difference-of-voltages/19545/2

Thanks! Also I found this way: I added a symbol and a dummy resistor,
setting the symbols Spice_Primitive and Value such that I get this in
the netlist:

BV1 /diff GND V=V(/input,/output)
Rdummy1 NC_03 /diff 1g

"V(/diff)" then shows up in the kicad plot menu. This also work for
other operations than diffing, for example

BV2 /mul GND V=V(/input)*V(/output)/100

It would be nice if one could simply append stuff to the netlist in a
textblock, is this possible?

> > Another thing, I found that one can use parameters for values, for
> > example {Rx} for a resistor value and then add a textbox with ".param
> > Rx=100k". Would it be possible to simultaneous get plots for a set of
> > different values of Rx?
> >
> Here you might try external ngspice.  KiCad 5.1.x has a direct
> interface, where you generate a netlist from your circuit and then may
> call ngspice. This will offer the full ngspice capabilities and plotting
> via ngspice or gnuplot. I have described an example at
> http://ngspice.sourceforge.net/ngspice-eeschema.html#external .
> Unfortunately this interface has disappeared in KiCad 5.9.9 . I still
> will have to make a wish list bug report to get this back.

Is this supposed to work on macOS as well? I downloaded the ngspice
package but the binary fails to run:

$ ./ngspice
dyld: Library not loaded: /opt/X11/lib/libXaw.7.dylib
  Referenced from: /Applications/ngspice/bin/./ngspice
  Reason: image not found
Abort trap: 6


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