# 10.5.4. Customizing netlister behavior with .json files¶

Instead of customizing netlister behavior on a component basis we can do it for all components with a selected name from a selected library.

The default configuration of a Spice Opus netlister for KiCad is defined in the pyopus.netlister.kicadsocfg module. You can dump this configuration as a .json file by typing:

python3 -m pyopus.netlister.kicad -d


The configuration will be dumped in a window. To dump it to a file named netlister.json, type:

python3 -m pyopus.netlister.kicad -d -o netlister.json


netlister.json is the name of the default netlister configuration file. It is written in JSON format. After it is dumped you can customize it and it will override the default settings for the library components that are specified in this file. It can also be used for customizing general netlister behavior. See the pyopus.netlister.kicadsocfg module for details. To apply the customizations we did for the Q4 transistor in section Customizing netlister behavior with component fields to all Q_NPN_BEC components from the device library we write the following netlister.json file

{
"Mapping": [
[
"device", "Q_NPN_BEC",
{
"Parameters": [ "m", "area" ],
"OutPattern": "#REF() (#PINS()) #MODEL() #PNV() #PV(Specification)",
"SpiceDevice": "npn",
"PinMap": [ 3, 1, 2 ],
"NamePrefix": "Q",
"ValueField": "Model"
}
]
]
}


Mapping is a list of lists with 3 elements. The first element is the library name, the second one is the component name, and the third one is an associative array holding the netlister configuration for the component specified by the first two fileds. The entries in this array were explained in section Customizing netlister behavior with component fields. The ValueField field specifies the name of the field to which the value of the Value field should be copied. In our example we copy it to the Model filed which is used by #MODEL() in the OutPattern. The model of a Q_NPN_BEC can now be specified with the Value field. If ValueField is null no copying takes place and the model should be specified via the Model field.

If one specifies null for library name and component name the corresponding associative array specifies the default netlister configuration applied to all components that are not configured explicitly.

Because KiCad stores copies of library entries in a local cache library the netlister will not find the correct mapping entry when a cached copy of Q_NPN_BEC is used. Therefore it is recommended to define mapping entries with null as library name. Such entries match a component only by its name, regardless of the library where eeschema finds the component. With this in mind the above example is more general if it is written as

{
"Mapping": [
[
null, "Q_NPN_BEC",
{
"Parameters": [ "m", "area" ],
"OutPattern": "#REF() (#PINS()) #MODEL() #PNV() #PV(Specification)",
"SpiceDevice": "npn",
"PinMap": [ 3, 1, 2 ],
"NamePrefix": "Q",
"ValueField": "Model"
}
]
]
}


netlister.json can also be used to change the behavior of the netlister. For instance file

{
"NetPrefix": "net",
"EnumerateNets": true,
"NetNumbers": 3,
"SuppressEnd": false,
"Mapping": [
[
null, "Q_NPN_BEC",
{
"Parameters": [ "m", "area" ],
"OutPattern": "#REF() (#PINS()) #MODEL() #PNV() #PV(Specification)",
"SpiceDevice": "npn",
"PinMap": [ 3, 1, 2 ],
"NamePrefix": "Q",
"ValueField": "Model"
}
]
]
}


specifies that the nodes should be numbered instead of using the KiCad-generated net names as basis for node names (EnumerateNets), the prefix for automatically generated node names should net (NetPrefix), the node numbers should be written with at least 3 digits (NetNumbers), and that the concluding .end line should be added if the netlist is a top-level netlist (SuppressEnd), See the pyopus.netlister.kicadsocfg module for details.

File netlister.json applies to all files generated from intermediate XML netlists in the folder where netlister.json is stored. Customization can be applied to individual netlists by naming the file <output netlist file name>.netlister.json.

Demo files for this section can be found here.