Power Flags and ERC Confusion

Ok I know this is supposed to be simple but I just don’t understand the errors I am getting in the ERC regarding the power flags, etc. I’ve searched all the posts I can find and other explanations, etc but I am still confused. The concept of the power flag is somewhat foreign to me as it is not used in other ECAD tools I have used. I get the basic premise and it is more for ERC purposes than anything else. I think they look odd on the schematic but that’s ok.

Per the default ERC table a bidirectional pin can connect to a power output pin without issue so after a bit I realized I probably don’t need a power flag on both GND flags shown below and that may be driving and issue.

I deleted one and re-ran ERC but get this:

The error moved to pin 8. It’s just not clear to me what the conflict is. If I remove the power flag from all GND connections (I don’t think this is right) then the error moves to some other location in the schematic where two inputs are tied together (GND flag pin is power input) and not driven by anything. Oddly enough it only balks at one location not the 20 where the same situation exists.

Any help would be appreciated so I can move into layout without worrying about the ERC errors. I have checked the netlist and all power and grounds are tied to same net respectively as expected so I probably can move on without fixing it but it is bother me nonetheless.

As far as kicad is concerned a bidirectional pin can be a push pull output pin that should not be connected directly to power as it would create a short. So either your j3-8 pin has the wrong type (J would imply connector. Connectors are normally set to passive.) or kicad is right and you indeed do something that might not be the best idea.

More detail see: Electrical type of schematic symbol pins (KiCad 4 and KiCad 5)


Man the community here is awesome, super fast responses!

Changing the pin type to passive for the connectors fixed it. I was looking in the wrong row of the ERC table and definitely see the conflict now regarding bidirectional and power output (which the power flag is defined as). The rationale regarding push-pull conflict makes complete sense.

Thanks, time to move to layout!


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