kicad-developers team mailing list archive

[Nick Østergaard <oe.nick@xxxxxxxxx>]

2014-04-05 11:09 GMT+02:00 Vesa Solonen <vesa.solonen@xxxxxxxx>:
> 05/04/14 01:23, Heiko Rosemann kirjoitti:
>> On 04/04/2014 10:45 PM, Carl Poirier wrote:
>>> I think this is a very good idea. I will add this to our upcoming
>>> KiCad library convention. Many transistors use letters already.
>>
>> I do not agree for footprints, because - at least if I understand
>> the proposal correctly - it will lead to many many different
>> footprints of the same housing, i.e. an SOT23-EBC, an SOT23-SGD
>> (for FETs), an SOT23-CBE, an SOT23-A1-C-A2, an SOT23-A1-C1A2-C2
>> etc. pp. with all the same dimensional data but different pad
>> names.
>
> This is the current state, because of the limited data model. I agree
> with you that it's not how it should be. Regarding diodes one can get
> _any_ orientation single ones in SOT-23
>
>> I came to kicad from Eagle some years ago and I still believe
>> distinguishing between symbol-package-device to be the best
>> solution for this problem.
>
> Second that. The implementation inside Kicad is not there yet. The
> symbol is somewhat hard linked to the footprint (because symbol have
> to contain matching pin numbers) and even the alias system can not
> solve the issue.

I never really started to use eagle beacuse of its wierd library. I do
like that the symbols are seperate from the footprint in kicad. (Or at
leat tries to)

> Diode pad names ought to be generated when the component is
> instantiated from the symbol, footprint _and_ "device description
> data". The device description data is currently embedded in the symbol
> and alias system, but that is clearly not working well enough.
>
> An example:
>
> SYM: Diode:->|-, pins:2, name:A, name:C
>
> FP: DO-214AB, pads:2, number:1, number:2, (numbers from JEDEC standard)
>
> Device 1
> DDD: Device: 5.0SMDJ11-UNI
>      symbol: Diode
>      footprint: DO-214AB
>      pin-pad-mapping: (K,1),(A,2) [no permutations]
>      manufacturer: Protek Devices
>      function: Transient voltage suppression 11V
>      keywords: TVS, zener, diode
>      data_sheet:
> http://www.protekdevices.com/Assets/Documents/Datasheets/5_0smdj.pdf
>
> Device 2
> DDD: Device: SS3H10
>      symbol: Diode
>      footprint: DO-214AB
>      pin-pad-mapping: (K,1),(A,2) [no permutations]
>      manufacturer: Vishay
>      function: Surface Mount Schottky Rectifier 100V
>      keywords: schottky, rectifier, diode
>      data_sheet: http://www.vishay.com/docs/88752/ss3h9.pdf
>
>
> Pin-pad-mapping is expected to contain all gate and pin swap
> permutations for devices that allow it, simple devices like
> bidirectional TVS zeners and resistors would just have x as a pin name
> for interchangeable ones.

I have a hard time visualising this workflow. I like the idea of your
DDD, but how or where is the pin-pad-mapping defined? Is this defined
in a cvpcb-like step? I see that the pin-pad-mapping definition
elliminates a bunch of the same symbols ans footprints with each of
their all possible pin combinations.

>>> As for capacitors, why not also using C and A for cathode and
>>> anode?
>>
>> In my experience, the terminals of a capacitor are not called
>> cathode and anode.
>
> Only polarised (electrolytic) ones will have cathode and anode, but
> elsewhere that would be misleading. Rolled foil capacitors used to
> have some marking which lead was connected to the outermost electrode,
> so one could make the orientation such that the outer electrode and schematic pins or net data.
> protected the other form interference (like capacitance changes from
> nearby objects). Precision polystyrene capacitors especially. Lately
> I've seen such in modern PTFE ones.
>
> -Vesa