Raspberry Pi Footprints & Templates

[russss]

This adds the following:

PCB templates for the full-blown RPi hat spec, and also for a Pi Zero "shield"

(they don't like you calling something a hat unless it's actually a hat)

A footprint for using a Pi Zero as a daughterboard-style component

...and also an M2.5 NPTH footprint used in the templates

[adamgreig]

Thanks, they look good. Is there a reference for what geometry these should be that I can check against?

[russss]

They're here for the Pi (this is the actual hat spec) and here for the zero.

Wish they provided DXFs but I doubt they'd import correctly into kicad...

[adamgreig]

All the other dimensions match the spec, so only issues are those I mentioned. The idea of PCB templates is obviously brand new though so I'm interested in how it works out in practice. It seems nice for this sort of thing (and Arduino and CHIP shields etc).

[russss]

The template idea is used by other libraries with the Pi in. The simplest procedure for using it is:

• Create the project (and probably close kicad due to an abundance of paranoia)
• Copy the template over the .kicad_pcb file
• When you're ready to start doing layout, manually change the ref of the connector to your schematic's component ref (e.g. J1) before importing the netlist.

The alternative is to have an entire template project with the symbol already in the schematic (seems like the official kicad library does this) but that seems more messy to me, and you'd still need to manually reset the reference of your connector if you renumber the schematic symbols.

I'll sort out the issues you spotted.

[adamgreig]

Does that work with the new kicad "import changes from schematic" option? I think it'd be worth adding a README to templates/ with instructions and explanation.

[russss]

It does seem to work fine, although that helpfully removes the mounting holes whereas the netlist update doesn't.

However, it seems like the mounting holes don't get removed if they're set as "Lock Footprint" so I'll set that on them (and perhaps on the connector as well)

[adamgreig]

3d model y-offset is the wrong way around (?!)

The 2.5 mm holes have a courtyard around the hole but not around the now-larger clearance. By comparison with the M3 hole vs M3 mount, I wonder if the M2.5 hole should remain a plain hole and then make the current thing an M2.5 mount and use that in the templates.

[russss]

OK, give that a go (my 3D preview is still mysteriously broken so I can't check it myself).

[russss]

(Also switched to M2.5_MOUNT. It would be cool to autogenerate these mounting hole symbols.)

[adamgreig]

3d model looks good.

I'm a little annoyed at the rpi spec for 2.75mm holes when an M2.5 should be 2.7mm for a close fit (the same as the 3.2mm for M3 I use here), or 2.9mm for a normal fit, but not 2.75. Could make the holes 2.70mm and still be within their 2.75mm but it's such a small difference it probably doesn't matter.

Agreed it would be nicer to autogen these mounting holes. I'll reconsider the diameter if and when that happens instead.