kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

On 3/30/2016 7:22 AM, Paul "LeoNerd" Evans wrote:
> Hi all,
> 
> At risk of opening what is a long and contentious subject, I'd like to
> start by asking a practical "how should I do X?" question, that will
> lead on to one of my main complaints about the way KiCad currently
> works and how I think it could be improved.
> 
> I am currently making a library part + footprint for a DCDC converter
> module - one of those little 2W black brick things. For example
> 
>   http://power.murata.com/datasheet?/data/power/ncl/kdc_mee1.pdf
> 
> These things come in two physical layouts with identical electronics
> inside. In SIL-4 configuration, the pins are
> 
>   1=-IN, 2=+IN, 3=-OUT, 4=+OUT
> 
> In DIP-8 configuration, the pins are
> 
>   1=-IN, 4=+IN, 5=+OUT, 7=-OUT
> 
> So my immediate practical question is:
> 
>   How should I represent this in KiCad?
> 
> Should I
> 
>   A) Make a single schematic library symbol for a generic "DC-DC
>      converter" whose pin names are IN- IN+ OUT- OUT+ and two
>      different footprints whose pin names match.
> 
>   B) Make two schematic library symbols with named (or numbered) pins,
>      one associated with each footprint?

B is the option I use. Typically footprint pad numbering is typically
constant between manufacturers even for SOT-23-3 components.  I do this
primarily because in the past I have selected the wrong footprint using
option A.  Option B gives me less chances to make this error assuming I
selected the correct schematic symbol.  In the end, you should use what
ever option your are comfortable with.  One of the goals of KiCad is to
not force a given work flow on the user.  Of course you could go the
fully defined part route where you have a single symbol with fully
defined user fields and the correct footprint already assigned to the
symbol.

> 
> I find the A) solution nicer because now I only have one schematic
> library symbol. Crucially, the upshot here is that I can sketch out my
> circuit design *before* I've committed myself to which physical part I
> want to use. It's certainly a lot nicer than B), wherein I'd have to
> change my schematic if I wanted to use a differently shaped (but
> electrically identical) physical part, depending on constraints of the
> board's layout or other concerns.
> 
> I also find A) nicer because it means that maybe one day in the future
> some manufacturer might come up with yet a brand new shape of physical
> part, but I can just reuse my existing schematic symbol for this. All
> fits in no problem.
> 
> <for ease of replies; continued in part 2...>
> 
> 
> 
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