Add sym/cmp/pkg/dev for Raspberry Pi Pico (SMD variant)

[fossum]

SUMMARY

Added Pico SMD to the library.

DATASHEETS / REFERENCES

Pico Datasheet

OPEN QUESTIONS / UNRESOLVED ISSUES

I can't verify footprint for a couple weeks as I board production takes time.

CHECKLIST

• Library convention page is empty.

• I have read and followed the library conventions¹.
• For packages, I followed IPC7351C (see details in library conventions).
• For modified elements, I bumped their version number².
• I already used the new library elements in a design and verified their correctness (optional).
• I'm the copyright owner of the added content (i.e. the changes are made by myself, not copied/imported from somewhere else).
• I agree to publish all my changes under the CC0 Public Domain License³, allowing everyone to use and modify the content without any restrictions.

¹ Library Conventions: https://docs.librepcb.org/#libraryconventions
² Minor version bump if only metadata was modified (e.g. "0.1" -> "0.1.1"), major version bump if functional changes were made (e.g. "0.1" -> "0.2")
³ CC0 Public Domain License: https://en.wikipedia.org/wiki/CC0

[ubruhin]

Thanks for the contribution! I updated this branch with several improvements. The package now also contains the test pads on the bottom of the Pico. I grouped these pins in the symbol to make clear these are located under the PCB since they will only be connected by reflow soldering (they're not directly solderable by hand).

To not break an existing design, I generated new UUIDs for all elements.

Actually it would be good to get a review on that, at least for the pinout and the most important footprint dimensions... Maybe @dbrgn could do that? Otherwise I'll merge in a few days...

[DoppioT]

Hello!

I had just started a project using the Pico W when I found this PR. Disclaimer: I'm an amateur in electronics and an absolute newcomer to PCB design, but I played around with Picos a bit, and I think I can contribute.

it would be good to get a review on that, at least for the pinout and the most important footprint dimensions

I've started reviewing. The dimensions are correct, for what I can measure, but the pads named A, B, C and D in the datasheet are missing. Those seem to be needed for reflowing

the abovementioned datasheet mentions:

The USB socket pins do not protrude all the way through the board, however solder does pool at these pads during manufacture and can stop the module sitting completely flat. Hence we provide pads on the SMT module footprint to allow this solder to reflow in a controlled manner when Pico W goes through reflow again.

As for

Does it make sense to have a separate symbol for the SMD variant?

In the H variant the pads are still electrically accessible if one is brave enough with a soldering iron (I am not, but to each its own) and if the geometry of the PCB allows it. I'm attaching a picture as an example.

On a separate note, the symbol should compatible with the Rasberry Pi Pico W, and the footprints are largely the same. Once this PR is merged, the W variant should be easy to add.

[ubruhin]

but the pads named A, B, C and D in the datasheet are missing. Those seem to be needed for reflowing

Good point! Added these pads to the footprint now.

In the H variant the pads are still electrically accessible if one is brave enough with a soldering iron (I am not, but to each its own) and if the geometry of the PCB allows it.

That's clear, but due to the space between Pico and PCB these pads cannot be soldered directly to the PCB, so the footprint shall not provide pads for them. Of course by using wires it would be possible in a hacky way, but I don't think footprints for such hacks should be part of official libraries (everyone would like to have it different anyway)...