[sdiy] Eagle footprints

[rsdio at audiobanshee.com]

On Nov 21, 2015, at 6:28 PM, john slee <indigoid at oldcorollas.org> wrote:
> On 22 November 2015 at 10:55, <rsdio at audiobanshee.com> wrote:
>> With status in the description, it's possible to note which projects have used a part. I just needed to change to larger SMD pads for a diode, and couldn't remember where it had been used.
>> 
> Unfortunately Eagle doesn't seem to store a description per device, only per set of devices, and also for the library containing it.
> 
> Looking at what it does store in the schematic file per device, I think one possibility might be to add an APPROVED attribute in the Technology section (where some of the CADSoft-supplied libraries store Farnell etc part numbers and other assorted metadata) when you've approved a device, and then search on that. This would be quite easy to then write an audit tool for. I've already extended the aforementioned Ruby gem to parse that part of the schematic (and various other parts).
> 
> Alternatively, you can add a description to a package. If you're reusing the same package for a variety of parts (eg. the same 0805 footprint for C and R) this might make sense. But it's not quite as sane for parts where you may reuse the same package for many devices but the pinout *also* needs to be approved, eg. TO-92 or ICs.
I definitely add descriptions to packages. I've noticed that the supplied packages usually include a URL for the data sheet where the package specifications originated, and this really helps for confirmation that the design is valid. When I can't simply copy an existing package, I create my own new packages from the manufacturer data sheets, so I try to do the same as a reference for the source of the measurements.

But you raise a good point - for every package in a set of devices, there's a potential that the pin-out could be wrong. So it would be helpful to have an attribute that serves as an "approved" status for a given pin-to-package mapping.

If you guys come up with any clever solutions in this area, please share.

Brian

p.s. On a related note, I mostly create devices for a particular part, naming the device with the part number. This works well for being sure that all the specifics are correct. Lately, though, I've been finding that it's more useful to have generic devices with lots of package alternatives, with less emphasis on a specific manufacturer or part number. When the part is highly specific, and has no pin-compatible alternative, the former approach works well. But when I need a diode, I'm finding it problematic that I have most of my diodes in my library as a particular part number, rather than a generic diode. So, I'm trying to create new devices to avoid manufacturer-specific designs as much as possible.