Kicad-to-HAL: Basic Schematic Symbols

The LinuxCNC definition of the HAL NOT component looks like this:

The loadrt command uses the “module name”, which is the file name of the module.

Functions and Pins use the “function name”, as defined by whatever code lives inside the module.

As a rule of thumb, module names will have underscores between words, where the corresponding function name will have hyphens, but this is not mandatory.

The numeric suffix on the Function name tells you which of the many identical components it is.

The Pin names generally have the Function name and numeric suffix as their prefix.

The NOT gate symbol in LinuxCNC-HAL.lib looks like this:

Note that there is no Kicad footprint: these components will never see a circuit board.

The symbol Reference (above the symbol: not.) must match the HAL Function name and must end in a period to make the Kicad numeric annotation easily separable. Jellybean components use the Kicad annotation as their identifier, so that the references will look like not.0, not.1, and so on.

The symbol Value (inside the symbol: NOT) must match the HAL module name; it will be lowercaseified as needed.

Kicad pin names must match the HAL pin names, must use only Kicad’s Input and Output “Electrical Type”, and must use only the Line “Graphic Style”. Kicad-to-HAL will glue the pin onto the Kicad reference with a period in between (not.0.out) for use in the HAL configuration.

I made the pins names visible for that screenshot. For a graphical component like this, I generally make them invisible.

The “Power input” pin is named “_” (a single underscore) and, in this case, is invisible. Kicad will automagically connect all such pins into a single net, so including a corresponding pin on a THREAD component (more about this later) will invoke Kicad-to-HAL magick connecting the function name (with the numeric suffix) to the appropriate thread:

addf not.0 servo-thread

The light gray + in the middle of the symbol (not quite centered in the O of NOT) comes from the LoadRT field you must include in the symbol properties:

That tells Kicad-to-HAL to add up the total number of NOT components and generate an appropriate loadrt command:

loadrt not		count=1

Not having to count the damn symbols, keep track of their numeric suffixes, and manually generate the addf commands justified this entire project.