kicad-developers team mailing list archive

[Jean-Paul Louis <louijp@xxxxxxxxx>]

Long before computer CAD software, we used Symbol for the schematic, and footprint or package
for the physical device.
What is a good reason to go away from that?


Just my $0.02
Jean-Paul
N1JPL

> On Mar 23, 2017, at 2:02 PM, Heiko Rosemann <heiko.rosemann@xxxxxx> wrote:
> 
> I strongly believe that's because many people come from Eagle originally
> (even via a different professional tool) and Eagle has this distinction.
> A symbol is what you place in the schematic, a footprint is what you
> place on the PCB and a component is what defines their relationship (and
> links to a datasheet etc.).
> 
> Example: A rectangle with three pins called VIN, GND and VOUT is a
> symbol for a linear voltage regulator, could be called v-reg. The
> footprint you choose for that symbol could be a TO220 with pads 1, 2, 3
> and heatsink, an SOT23 with pads 1, 2, 3, an SO8 with pads 1..8...
> 
> The component "LM78Lxx" defines that for a variant LM78LxxACM, the
> footprint is SO8 with Pad 1 used for Pin VOUT, Pads 2, 3, 6, 7 used for
> Pin GND, Pad 8 used for Pin VIN and Pads 4 and 5 are Not Connect, for a
> variant LM78LxxACZ, the footprint is TO92 with Pad 1 used for Pin VOUT,
> Pad 2 used for Pin GND and Pad 3 used for Pin VIN.
> 
> In KiCad, we have a mixture of "symbols" to which you can assign "any"
> footprint and "components" which have a footprint specified, and we call
> both "symbols". Some of these symbols have pin numbers called "1, 2, 3"
> to fit certain "neutral" footprints, some have pin numbers called "VI,
> VO, GND" to fit a certain "special" footprint, some have multiple pins
> for the same function... the 78(L)xx-series in the libraries I got for
> stable-4.05 is a good example of this mixture, and it used to be much
> worse a few years ago.
> 
> But then again, we have this discussion about once a year and it always
> peters out after a while because nobody has the time to actually
> implement a proof of concept (me included) so it can't properly be
> evaluated, while the librarians do a great job improving the "standard
> library" so people have it easier and easier to just use what's provided.
> 
> (What I'd definitely love to see: A more prominent warning if your
> symbol has some pins that don't have matching pads in the footprint you
> have assigned them. Preferably in cvpcb or whatever dialog will replace
> it, not 10 clicks later when you're importing a netlist into pcbnew.)
> 
> Just my 2 cents,
> Heiko
> 
> On 03/23/2017 03:14 PM, Jon Evans wrote:
>> I agree with Simon.  I have plans to propose something like this in the
>> future (i.e. an integrated part library that manages
>> symbols/footprints/etc together) and it would be best to reserve the
>> term "component" for this future use, since in my experience that's what
>> "component" means in the big tools (I have not used Altium, but it is
>> more of a "medium" tool than a "big" tool FWIW)
>> 
>> I don't have time to detail my proposal now, but basically I think a
>> "component" should map to one or more footprints, one or more symbols,
>> one or more vendor part numbers, one or more 3D models, etc.
>> 
>> -Jon
>> 
>> On Thu, Mar 23, 2017 at 8:33 AM, Simon Wells <swel024@xxxxxxxxx
>> <mailto:swel024@xxxxxxxxx>> wrote:
>> 
>>    one of the things that irks me about component is even though its
>>    meant to only be schematic being component libs a lot of the questions
>>    asked in irc will state component when they use that as either a
>>    generic term for symbols AND footprints or sometimes footprints only,
>>    as to some i guess thats still part of a "component definition".
>> 
>>    If at some point down the line we did introduce some sort of package
>>    that was symbol/footprint/model/spice/....... i think that would be a
>>    much better thing to call a component.
>> 
> 
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