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  • Author Author: Jan Cumps
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KiCAD 8: RX23E-B kit - LCD schematic (and using a bus)

Jan Cumps

I'm building a PCB for Renesas' RX23E-B microcontroller. In this post: the LCD pins. I'm also using a KiCAD bus for the first time since V4. It changed a lot.

image

The crossed-out resistors are "do not populate". These LCD signals use the same pin as other functions on the board. I don't really need the resistors, if I don't plug the LCD in. But they are just empty footprints. The cost can be neglected.

Using a BUS in KiCAD 8:

In early KiCAD, a bus didn't hold a lot of intelligence. It was a blue line where you could connect signals to. In newer KiCAD versions, this has changed. A bus has structure, and knows what signals it holds. It can be a combination of signals, or a range. In my case: both. The LCD bus holds 3 ranges of signals: 4 voltage pins, 4 communication pins, and 40 segment signals.

I first defined the bus in the schematic setup:

image

Then I routed signals from the microcontroller to the bus, and from bus to LCD connector. The wires are (have to be) labeled at both sides.

I used global labels to indicate those shared signals, because they are shared in other sheets of the design. Example: with the timer that I use for AC excitation:

image

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  • I don't know if it will help or not since you've already completed the bus layout, there's some time-saving suggestions in this video: https://www.youtube.com/watch?v=T5Zy_BWg3Tw - hopefully you found some ways to speed up things anyway.

    Some of those things can help to speed up using buses a little bit (because some of it is excruciatingly long-winded workflow compared to say EAGLE buses). Some of it puts me off using buses with KiCad, but for your use-case, it's pretty essential since there are so many signals related to LCD!

  • in reply to shabaz

    I didn't see the video. I found a post that suggested similar actions. 

    In reality, I spent more time unlearning my KiCAD 3x habits, than completing the schematics. 
    Initially, I wanted to do individual wiring, but that is a real mess in this case - even if you restructure the IC and connector drawings.
    The bus makes it neater for situations like this, with a set of related signals.

    The bus functionality in KC8 schematic designer is not bad at all. 

    What do you think of my style to branch off wires from both sides of the bus?

    image

  • in reply to Jan Cumps

    Looks very good. It is clear those signals are attaching to a bus with those 45-degree bends, and well-labelled too. Easy to understand!

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