I’m working on a schematic that uses a T4 MCU. It is powered from an external 5v USB source and the T4 MCU derives a 3.3v output on pin 46 and is defines as an output.
However I do not understand how to connect this pin to other components on the schematic that use this 3.3v output as an input. Everything I’ve tried generates errors, some 3.3v inputs has no errors See attached screenshots.
Insight and help appreciated.
As I remember from forum discussions the error likes to be reported on one point at net. So if you have many power inputs connected together and with no power output at that net the error can be reported for only one of that power inputs pins.
But I’m not 100% sure as I never run ERC.
An Output must connect to an Input and they must be on the one net.
If you have, eg, a resistor between the output and the input, you have two nets, so ERC will show an error or warning.
You need to use power flags or ignore the warnings.
This messing around is mainly why I do not use ERC either.
@jmk and @Piotr, are you both saying that a physical “wire” must be run from pin 46 (3.3v output) to those points that require this 3.3v as an input?
I’m quite new to KiCAD and EDA in general.
A single net must run between the pins to satisfy ERC, so yes an unbroken wire must run between the pins to satisfy ERC.
If the wire (net) is broken by any symbol, ERC will not be happy.
To keep ERC happy, if there is a symbol blocking the path, you can:
Use power flags,
Change the electrical type of pin property
What pins in the lower part are to connect to pin 46 up top?
Ok, I ran a physical wire from pin 46 down to the two areas shown on the other JPG image that had 3.3v power symbols arrows and removed these power symbols. And I’ve tried putting the Power Flag symbol on these to no avail and usually adds more errors pointing to the flags.
So now a dedicated wire runs to join those points needing 3.3v inputs, but an error still existing on pin4 (a 3.3v input labeled VDD) in the attached image and now this is the only ERC error.
What is the warning ERC gives about the connection?
@jmk, this is the 1 error I get now. Why aren’t you responding via the forum?
And that is how the symbol pin is defined as well…Power input.
He he, I just moved your post to the right thread. You posted it on the wrong thread 
Where is the T4 MCU in the library, or is that not its full name?
thanks @jmk, not sure how that happened. Well I’m not the creator of the “project” so when I look for them I find several in several places.
The T4 libraries are in the project Libraries folders. Under a “Library” sub folder are:
Under another sub folder are:
I’m not sure which is used or referenced, or know how to tell. 
I wanted to know how pin 46 is defined in the symbol.
In the schematic editor, Right click the T4MCU symbol, select Properties, up the top select Alternate PIn Assignments, then towards the RHS is a column titled “Electrical Type”.
Please tell me what pin 46 is labeled?
I mentioned this earlier. Pin 46 is defined as an output, which it is. It is THE source for 3.3v regulated DC from the Teensy 4.0 or 4.1 MCU.
I didn’t know if this was the data sheet definition or the symbol pin definition… who ever drew the symbol may have defined the pin as anything.
As one is in and the other out, it must be because they have different names ie. One is vcc and the other 3v3.
I’m just checking.
Sorry, I don’t have a solution for you.
You will probably have to wait for someone in Europe or US to wake up and offer a solution.
Thanks for your help.
It is the symbol pin definition. The Teensy 4.1 has multiple symbol pins that are labeled 3.3v, pin 46 is an output, pin 15 and 51 are labeled as inputs, so that’s weird.
Thanks again.
I think I may have found the problem I posted on this forum. It looks like the Teensy 4.1 symbol has some incongruities with what is a 3.3v pin much less an output pin.
I will update this post once a resolution is confirmed.
There is a difference between “output” and “power output”. If the pin is just defined as (data) output, it won’t power “power input” pins. You need to set the pin type to “power output”.
pin 46 also shows at the very top as 3.3V
I couldn’t find a suitable Data sheet.
Going back to the place where I finished (it was 2:00 here when I written my last post)…
Physically you have to connect them by copper (can be said ‘wire’) but at schematic you can connect them in any way - you can use labels, you can use power symbols and of course you can use also wire.
You did as I expected reading your previous post. It is not what you should do. Running power wires makes unneeded mess at schematic.
Output pin ERC understands as something that can be connected with input. But ‘power inputs’ need to be connected to ‘power output’ and not (signal) output.
But it is a temporary fix to help find a problem 
