Hierarchical pins


#1

Hello Everyone, please help with some tutorial on how hierarchical pins are used to connect to a micro processor. I have sub schematics and a Micro processor and would like to connect those and have have no idea which pins connects to the exact micro processesor pin. I have some similar pin names which I can connect but I dont have any idea on the other pins as their names are different. I know this is a noob question but I am a beginner in electronics (Mech engg.) Thank you.


#2

Hierarchical pins are simply lables that allow you to get from a hierarchical sheet to the sheet that contains it.

So a small tutorial about hierarchical sheets might help.

Step one add a hierarchical sheet in the main sheet (I call it processor.sch and give it the designator processor 1.)

Double click on that new sheet and you will see a new empty sheet. I add some pic micro processor to it and simply connect two of its pins to a hierarchical label (=pin) (I also assign a valid 8 pin footprint without concern if this is the correct one. this is simply to showcase later on the pcb side what has gotten connected.)

I also connect the vcc and gnd pins of the processor to power labels to showcase that these are global.

In the end my lower sheet looks like this:

Now i need to add the two hierarchical pin to the “symbol in the upper layer.”

For that i go back one layer (using the ascend/decent hierarchy tool found in the right toolbar for kicad 4 and in the top toolbar in nightly/kicad 5)
Rightclick the “symbol” representing the sheet and select the import sheet pin entry.
A pin will appear at the edge of the “symbol”. you can move it around using the mouse. If you are happy with the position of that pin you leftclick to add it at the current position.

Repeat that process until all pins you added inside the sheet are visible in the “symbol”.
In our example it will then look something like this.
For the purpose of this small tutorial i simply add a 4 pin connector symbol (and connect it to some 4 pin pin-header footpritn)
I connect two of the pins to the hierarchical pins of the symbol and two further pins to the power labels i used inside the sheet.
In the end the schematic should look similar to this.

And now lets look at what pcb would be created from this.

You can see that all 4 pins (both the ones using the power symbol and the two using the hierarchical sheet have been connected.


I hope this helps a bit. If you still have questions feel free to ask (I made this tutorial in a hurry and do not expect it to show everything. So i will most likely have missed some things.)


#3

This is a great effort to help a beginner. Thank you. My question is I have so many pins with different names and I want to connect them to ESP WROOM 32 with 38 pins. I have optocoupler, Ethernet, POWER, LDC etc to be connected to ESP WROOM 32. The pins names are different on the Microprocessor and the sub schematics. I want to connect them but dont know which pins goes to which pin. I hope you understand my question . Thanks aghain.


#4

I think a screenshot or two might help


#5

Below you can see the whole setup and I have connected some pins.

Now I want to connect other .sch to the u processor and I am unable to do because I do not know which pin to connect as the names of the pins are different.

I think I need some knowledge in electronic pins . Sorry if this was noobish.


#6

Try to follow my tutorial. If you get the same result as i represent you should at least have some understanding on how it can work.
Then go from there. (One step at a time)


#7

I am sorry if I am irritating you, but before creating PCB, I need to join all the schematics and add footprints as you know. I am struck at wiring the .sch files with u processor.


#8

Have you tried my small example?

It would help me a lot if we would work on the same project and see where the problem is for you.


#9

I have done your example and fortunately, I know the procedure you tried to explain. In my screenshot 1, on the left side you see 3 pins which are not connected. I want to connect those 3 pins to the microprocessor (I know how to connect) but dont know where to connect. I am checking with the u processor datasheet if I can get some info. i hope you understand my problem.


#10

Ah so you don’t have a problem with the kicad side but with the design of the circuit it self. That explains why my answers did not help you at all.

And yes you will need to check with the datasheet what you can connect with what. If other people are involved in this project you might want to talk to them as they might know about further restrictions.

Some microcontroller producers also have dedicated tools that help with pins configuration. This tool can be used to test if your decided setup works. (there are often strange restrictions with pin assignment that are easily overlooked. For example giving one pin a particular function can restrict what other pins can be.)


#11

Thank god you got it. :joy::joy: Yeah I will find some person. Lastly, if possible, just help me with a link or something useful with the pin connection. Thank you for your time.