Multi-Board Layout


#1

I have been looking into making a design that would have a central control board, which then controls separate LED panels for 7 segment displays. If I had this all on one board, it would have 120 wires running out of the board, with with seperate panels, I can bundle it up into some nice ribbon cables (or even less, if the i2c drivers are on the individual boards).

The best resource I can find on this forum is this, and elsewhere I have found reccommendations to make a breakaway board, and have that single board made.

  1. Seeing as that link is pretty old, has multi-pcb been included in a more recent release of KiCad?
  2. If not, how would I go about making breakaway PCBs in KiCad?

#2

Not that I am aware.

https://forum.kicad.info/search?q=panel https://forum.kicad.info/search?q=mousebites

#3

I’m not an expert at this yet, so there may be a better answer then mine that comes along.

Your post is lacking a little bit in the details; and that will also reflect in the quality of my reply; but my advice will be worth exactly what you paid for it. :sunglasses:

1.) I highly recommend that you use a data bus instead of ribbon cable. I2C may/may not be optimal for your design, but there are other protocols.

2.) It would probably be easier to layout the actual PCB easier if each board were designed separately, then manufactured in the quantities needed. Otherwise you are going to end up with significant duplication’s in both the schematic and board layout that really are not needed.

I have a design to talk to different boards. In Eeschema, what I did in the creation of the design was to put ONLY the “RX circuit” at the end of the TX design; and the “TX circuit” on the front of the RX design. This helped me to visualize how the bus data was going to be handled. When the design was completed, I deleted these extra circuits so they would not interfere with the PCB design.


#4

There is nothing stopping you having several boards on one panel, but:
All annotation must be unique across the entire project
You will get DRC errors about unconnected nets eg GND between boards, ignore them
The PCB fabs will charge you a higher fee, they are aware that you are avoiding multiple setup charges


#5

OY! or EEK! In my past life I was a repair technician. I’d HATE LIFE if that were done to me on a product. I suppose if the board is small enough in part count, it could be done with parts numbered in 10’s or 100’s, as in U10, R10, and U20, R20, etc.

So, are there any other GOTCHAS that I can’t think up for doing it this for small one-of projects?

I thought the idea was kinda neat at first for a couple of reasons, but I mainly ditched it because I didn’t want to spend the time to re-draw and reconnect everything on both the schematic and layout.

And, on my boards, my parts have select-able software ID addresses on the bus. Planning on going to have manufactured and I’m not sure how much more complex this would make the assembly. With the same annotation it is easy to state, populate only R1, R5, R7 on the first 10 boards, then R2, R3, and R6 on the next 10 boards.

I think I’m glad I already decided to NOT do it this way. :+1: