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Re: eeschema for IC design


On 14/10/2020 20:00, pepijn de vos wrote:
> Hey all,
> I'm a sw dev and recent IC design graduate, who made it his mission to
> improve open source tools for IC designers.
> To this end I've been playing with the recently released Sky130 PDK,
> which is an open source PDK that does not require any annoying NDA's and
> will actually allow sharing IC designs.
> I've been looking at eeschema a bit as one of the options to do
> schematic entry and simulation. However, I found that the integration
> with ngspice is very limited at the moment. So I'm interested in making
> this better!
> The first problem I ran into is that it can't plot the currents of a
> transistor no matter what you add in terms of spice directives. More
> info:
> https://forum.kicad.info/t/how-can-i-plot-transistor-currents-after-a-simulation/25324/8
> So I have several questions.
> Would this be a good first issue to tackle?

Hi Pepijn,

Sure, go for it - and if you'll find it too hard as a starter, there's a
ton of other issues in the simulator/ngspice integration...


> I think there are a few ways to go about it, which don't exclude each
> other. One is to extend the logic that adds the currents for voltage
> sources and resistors to also add transistors. Another is to update the
> simulator UI to populate the signal list from the raw file, rather than
> its own idea of which signals were saved, so that you can add custom
> .save statements and plot them.

I would by default tell the simulator to log all node voltages/pin
currents (including transistor pins). Anything else (that is internal
currents, etc.) should be parsed from .save directive (so I'm more in
favor of option 2).

> For example, two other things that would be great to add is a way to
> plot algebraic expressions of different signals,

This looks like a nice feature in the longer term. If you're interested
in developing it, I could offer some (but not much) help due to my
current workload...


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