spice simulator: power symbol a floating point separator

[Eldar Khayrullin]

If I use a power symbol with comma separator (like +3,3V) the simulator log shows:

Node Last Voltage Previous Iter
---- ------------ -------------
net-_c2-pad1_ 0 0
+3 0 0
3v 0 0
vc1#branch 0 0

Spice think about two nodes +3 and 3v.

Application: eeschema
Version: 201609180819+7176~55~ubuntu16.04.1-, release build
Libraries: wxWidgets 3.0.2
           libcurl/7.47.0 OpenSSL/1.0.2g zlib/1.2.8 libidn/1.32 librtmp/2.3
Platform: Linux 4.4.0-36-generic x86_64, 64 bit, Little endian, wxGTK
- Build Info -
wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8)
Boost: 1.58.0
Curl: 7.47.0
KiCad - Compiler: GCC 5.4.0 with C++ ABI 1009
        Settings: USE_WX_GRAPHICS_CONTEXT=OFF
                  USE_WX_OVERLAY=OFF
                  KICAD_SCRIPTING=ON
                  KICAD_SCRIPTING_MODULES=ON
                  KICAD_SCRIPTING_WXPYTHON=ON
                  BUILD_GITHUB_PLUGIN=ON
                  KICAD_USE_SCH_IO_MANAGER=OFF
                  KICAD_USE_OCE=ON

[jean-pierre charras (jp-charras)]

In net names, when they are used in spice simulator, there are a few constraints:
- some chars are not accepted, because they are separators in directives, for instance ,{}()
- AKAIK, but I can be wrong, only ASCII7 char set is allowed

Currently, only '(' and ')' are replaced by _, because unfortunately I used these char in default net names, and the spice netlist generator replaced these not allowed chars by _ since a long time.

I am not sure replacing not allowed chars in net names is a good idea.
It can create other issues.
An user who want to use spice simulator should know the spice constraints, and must comply and live with them.

[Eldar Khayrullin (eldar)]

Maybe KiCad should to preprocess your own netlist to spice simulator constraints.
If KiCad replaced ',' by '.' it will be OK because KiCad now replaces ',' by '.' in Value fields.

I want to have one file that compliance to my standards and usable without modifications with simulator - it will be ideal.

[jean-pierre charras (jp-charras)]

I perfectly understand what you want (I have the same problem in France).

My concern is the fact replacing not allowed chars in spice netlist by another chars can create conflicts (there is a risk to create duplicate net names)
This is very easy to do in Kicad code.
The question is more:
Should we do that?

"If KiCad replaced ',' by '.' it will be OK because KiCad now replaces ',' by '.' in Value fields":
This is not the same case:
This change just create strings (mainly values) compatible with spice requirements, and (AFAIK) cannot create conflicts.

[Eldar Khayrullin (eldar)]

I don't think that it is possible to have '+3.3V' and '+3,3V' nets or others same because commas and dots uses how floating-point separators.

[Jeff Young (jeyjey)]

I looked into this and while we handle ',' to '.' conversions in numeric fields, the net names are strings. So you can in fact have a schematic with both 3.3V and 3,3V nets (and they are treated as distinct nets).

We could auto-convert those nets that don't produce collisions. But that leaves the results unpredictable.

Better would be to check for collisions with *any* nets needing conversion, and only convert if they are all clean. But there's still a level of unpredictability with that approach.

I'm going to bump this to a wishlist and see if it gets any traction with the user base as the number of folks using the SPICE integration increases.

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2033