> On Jun 8, 2015, at 12:19 PM, Heiko Rosemann <[email protected]> wrote: > > The "components library" is the approach Eagle uses, and I have a bit > of Eagle experience, so let me try to explain... > > In that approach, you do _not_ place just a symbol in a schematic, but > an entire component (maybe a TL072ACD) or a component for which there > are several variants (maybe a TL072A with the variants CD and DE, one > a SOIC8, the other a PDIP8, but same symbol). > > This makes the creation of new components and variants very easy, as > long as the symbol and the package (Eagle speak for footprint) exist. > All you have to do is to give it a name and "connect" symbol pins to > footprint pads. This last step is basically what you used to do with > CVPCB, only you do it only once, when you create the component. You > don't have to do it for every TL072ACD in your schematic (where I > agree it's very error prone), and it's more flexible than CVPCB, > because it can connect pin 1 (symbol) to pin 3 (footprint) or pin E > (symbol) to pin 3 (footprint) - so you don't need the > TO220BCE/ECB/CBE/123 footprints.
For the record: I’ve never used CvPCB, and I’ve always thought that it was a mistake. I have always embedded footprint (and custom part numbers) into my schematic symbols. > So you have a single "canonical" version of each footprint and symbol. > No need to copy symbols for creating new components, no need to update > or even touch all your OP-Amps when the one you based your symbol on > shows a bug. > > Or in other words: It takes your "library with a few of your favourite > OP-Amps, each with the correct footprint embedded" one step further: > The components only link to symbols and footprints. OK, so this “component” library is something that maps symbols (from a symbol library) and footprints (from a footprint library) into a third library, in much the same was as Altium does with their Integrated libraries. > If you place a > component in a schematic, it shows the symbol linked from it, and > stores the information of available footprints to be used when you > create a PCB from the schematic. A given component should have exactly ONE available footprint. If your opamp comes in PDIP-8 and SOIC-8, those are two different components. > If you place a component on a PCB, it > shows one of the footprints it links to (or a selection dialogue). Here’s a question: why would you place a component on a PCB? That component has no connectivity information, and Kicad won’t (and IMHO, shouldn’t) let you edit the netlist in pcbnew. (How should it regenerate the schematic when you do that?) So I see what you’re saying … the “symbol” library should contain symbols only, and have no connection to a footprint, and you need a component library to map a symbol with a footprint (and a 3D model, and a custom part number for the BOM). The engineer doing the design interacts only with the component library; only the librarian needs to be concerned with the symbol and the footprint libraries. Gotcha. From the perspective of the user who considers each symbol to be a component (again, that is: embedded footprint, embedded custom part number, different symbols for TL072ACD and TL072ACP) and ignores the CvPCB crap, there’s not much benefit to a separate component library. That is especially true given the inability to edit a netlist in pcbnew. -a _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
