Hi,
I am doing the KiCad unlocked tutorial from Pat Deegan.
When running the ERC I get some errors which I haven’t been able to solve, one of them is related to the VBUS power symbol shown in the screenshot below.
In the screenshot I have used the VBUS power symbol twice, only one of them give me an ERC error. Could someone please help me, explain why one of them is giving an error while the other seems to be fine and how to solve it.
Thank you
There are several different issues ,here, and you have not shown the list of ERC violations.
The title of this thread:
ERC error: Input power pin not driven by any Output Power pins
Is probably related to pin 7 of your IC (VREGIN). ERC in KiCad does not have spice capabilities. It just compares connections within nets, and it does not know your zero ohm resistors are shorts.
For the rest. Look up the usage of the PWR_FLAG symbol in the manual (or this website) It’s the most common problem with ERC.
Imagine if you use 30 times VCC (or GND) symbol and ERC wants to show you that there is a problem with VCC (or GND) net.
Would you like to see exactly the same Error 30 times if it is really only one Error.
Sorry for not being clear. The ERC violation I’m having trouble with is for the VBUS symbol on the left of the screenshot, the one connected to R7. It’s highlighted and pointing directly to the pin on the VBUS symbol. For the other VBUS symbol, the one connected to R9, there are no ERC error related directly to the VBUS symbol, only for the IC REGIN pin. I fail to see why one VBUS symbol has an error while to other is OK.
In the root sheet I have a VBUS symbol which is connected to a PWR_FLAG.
It would have helped if you had gotten rid of those other 6 ERC violations and their arrows first.
For KiCad, anything connected to VBUS is just a single net, and KiCad places the ERC arrow on a “random” location. It may seem illogical to a human, but for ERC it’s very difficult to predict what the “best location” for showing the error is.
To me, it looks like there is a problem with:
Keep a keen eye on small green squares and red circles. Both are indications of KiCad not recognizing a connection.
Another possible cause is with the labels themself. For some (inexplicable to me) reason KiCad accepts spaces in label names (even leading or trailing spaces) and such spaces create a new net name, and thus a new net. You can use the net highlighting tool to verify whether KiCad recognizes the connection via the power symbol over the different sheets.
You can ignore the ERC power pin message which is false.
I see; it is not an error related specifically to that symbol, but in general to the VBUS net.
I will try to find the root cause of the error.
Thank you for your help.
This is a common struggle with ERC. The documentation has just been expanded specifically to cover this in more detail:
And to some extent also the prior section:
If there’s any way to improve it further, suggestions are welcome!
Oh good, a post we can reuse when the question is posted in future.
