Enable "personalizing" of subcircuits by adding parameters to the instance line

[Holger Vogt]

The accompanying example of a potentiometer (device:R_POT) does show it:
In the eeschema circuit drawing, in the line

R_POT wiper=0.3 val=100k

the tokens wiper=0.3 val=100k are ignored when creating the ngspice instance line

XRV1 "/VDD" "/out" 0 POTI

in the netlist. It is desirable to have

XRV1 "/VDD" "/out" 0 POTI wiper=0.3 val=100k

instead. Thus it would be possible to simulate different potentiometers just
by adding some parameters to each symbol value field and finding them at
the end of the instance line XRV1... in the netlist. Of course the
corresponding subcircuit in the lib file has to show the same parameters
in its .subckt line. But only a single subcircuit in its ngspice lib file
would be needed then for all different potentiometers in a circuit.

[Holger Vogt (h+vogt)]

KiCad version used in the above example:

Application: Eeschema
Version: (5.1.0-599-gde055031a), release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.61.1 OpenSSL/1.1.1 (WinSSL) zlib/1.2.11 brotli/1.0.6 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) nghttp2/1.34.0
Platform: Windows 7 (build 7601, Service Pack 1), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
    Boost: 1.68.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.61.1
    Compiler: GCC 8.2.0 with C++ ABI 1013

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[Juan José (blascoburguillos)]

I'm also affected by this bug. Additionally the program completely crashes in arch:

https://bugs.launchpad.net/kicad/+bug/1835547

[Jonatan Liljedahl (kymatica)]

I do this all the time, exactly for pots. See attached screenshot.
The "pot k=0.25 r=100k" is the Spice_Model field.

The sub circuit looks like this:

.SUBCKT pot 1 2 3 r=100k k=0.5
*
R1 2 3 {r*(1-k)}
R2 1 2 {r*(k)}
.ENDS

[Pepijn de Vos (pepijndevos)]

The solution proposed by Jonathan indeed works for me.

However, it would be great if there were an option to display and change the individual parameters in the schematic. Currently it only appears to be possible to display the entire Spice_Model parameter.

Maybe there could be either a way to pass symbol parameters to spice, like Spice_Model="pot k={k}", or make special parameters like Spice_k, which would pass k to the model, etc, etc. there are many ways to go about it. The end goal is that it's easy to see and change the parameters passed to the spice model.

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2426