Electrical-rule checking depends on how symbol pins are modeled. If every pin is declared passive or unspecified, the drawing may produce fewer complaints while providing less useful checking. Choose electrical types from the actual pin function, then verify that the checker can detect the errors the design is vulnerable to.
KiCad’s pin electrical-type convention links pin type to electrical function. Use the component documentation to make that decision. A pin’s graphical direction on the page does not determine whether it is an input, output, supply, or another electrical category.
Review the functional role
For each pin family, identify who drives the connection and under which operating conditions. Distinguish push-pull outputs, open-drain behavior, bidirectional signals, passive terminals, and power connections where the tool supports those categories. Pay attention to pins with selectable functions, because the intended mode may affect the appropriate representation.
Do not change a type simply because two connected pins trigger a warning. First determine whether the circuit is wrong, the symbol is wrong, or the checker configuration lacks the intended rule. Those cases require different corrections.
Test the library in a small schematic
| Review case | Expected behavior to examine |
|---|---|
| Valid source connected to its receiver | No misleading conflict for the intended use |
| Two incompatible drivers joined | A useful diagnostic under the selected rule map |
| Required input left without a source | An appropriate connection warning |
| Supply modeled incorrectly | A diagnostic that leads to the actual missing source |
Construct these cases in a disposable library review project. Record the expected and observed result. The purpose is to understand coverage, not to tune the checker until every example passes.
Keep exceptions narrow
Some legitimate circuits require context that ERC cannot infer. Document the specific exception and why the connection is valid. Prefer a local, explained treatment over weakening the symbol for every future design. A library-level change can affect many projects that do not share the exceptional use. Record the intended operating mode beside any mode-dependent exception so a later reuse cannot inherit the justification blindly.
- Approve the pin-type table against the device’s functions.
- Retain the small test schematic and checker configuration.
- Review warnings in the real circuit without suppressing them wholesale.
- Revisit coverage when operating modes or library definitions change.
ERC is a consistency check, not a complete simulation or proof of device limits. It cannot validate every voltage, timing, or startup condition from pin types alone. Combine it with the physical pin-map audit and the design’s functional review.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist