Here I have a circuit that sources power from a computer through a USB-C receptacle. The USB-C receptacle is the “starting point” of the circuit in my schematics and it provides power to the entire circuitry. So it would make sense to set the VBUS and GND of the USB-C receptacle symbol as Power Output, and all power input pins of other components as Power Input. Then when I performed ERC I ran into two errors:
I have to short the two VBUS and GND due to symmetrical orientation of USB-C but doing so I get the error “Power output and Power output are connected” because all four pins (the two VBUS’s and two GND’s) are set as Power Output. If I set one of the two VBUS or GND to Unspecified I’ll just end up with many more ERC errors at connections with other components. I can’t figure out a way to get rid of this error.
For any components that source power directly from the USB-C receptacle (VBUS and GND), I get the ERC error “Input Power pin not driven by any Output Power pins” at its input power pin. Why this happen and how to clear this error?
Use a power flag symbol. There is a lot of discussion on this forum explaining why and when it’s used. You can search for “input power pin not driven” to get those results too.
Using the PWR_FLAG symbols is one way to do it, but changing the output pin type of the connector should also work. You have two issues in your schematic that prevent it from working though.
On the left side you have:
I assume you’ve changed both the A9 and B9VBUS pins to an power output, and that means you have shorted two power supply pins, and that does not work in KiCad.
On the right side you have:
This is because JP6 breaks the connection between the power output of J1 and the power input of U3. KiCad does not know that a jumper is a short and the nets are connected.
So in the end, because of jumpers JP2 and JP6, changing the ouput pin types of the USB connector does not work and you have to either use the PWR_FLAG symbols anyway, or change the jumper pins to the power output type too.
For your first problem, why is your symbol having different pins for the same power output? You’d probably just use one power output pin and stack the other pins with the same position on the same pin (make them hidden and passive I think). Alternatively, you could just have one power output pin and assign the same pin numbers in the footprint.
The second problem happens, because jumpers don’t let the power through ERC wise (KiCad has no idea if they’ll be open or closed). Add a power flag symbol on the right of the jumpers or turn pin 2 of the jumpers into a power output again. (But then be careful so you don’t have both outputs active at the same time again, so only do that with either the USB or the EXT jumpers)
