Parts and Footprints

Software
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The open source project that I’m looking at is supposedly changing to KiCad and I wanted to get a head start by trying it.

The first part I opened in Schematic Editor was the Atmega2560(TQFP100), but when I got to the PCB editor there is no footprint. It searched the web but found nothing.

I found the official KiCad parts library, but it only seams to have the std library that I have in 4.0.1.
Is there a place for user created parts sharing.

I just spent a month working out how to create a part from scratch in Fritzing, and was not looking forward to doing that again, but I looked up videos of how to make footprints in KiCad and it seams that they don’t really care if the silkscreen outline of the body of the part is that accurate. I thought the outline would be critical so that you know if parts will hit in the PCB layout stage, so I was wondering how accurate are the footprints in the library.

I’m only a beginner in this electronics thing - I knew nothing 3 mounts ago -, so it’s been quite difficult.

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As far as I know everyone sets up their own repository if they want to share footprints etc, or else they contribute them to the official library. Maybe no one bothered with a QFP100 footprint because they can get that from any number of parametric footprint generators.

People with varying degrees of skill contribute, so there is no guarantee that the silk outline has anything to do with reality or that it is in any way sensible - if you want something done a particular way you have to do it yourself. The other thing is that the silk layer is not the place to indicate the region taken on the board - that’s what the courtyard layer is for.

What project is it that’s supposedly switching to kicad?

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Sorry, it’s just a bit daunting/frustrating when you don’t know anything.

Parts are murder to create in Fritzing - my 1st part took over a month because I had to learn Fritzing, then Inkscape, then XML -, so I was hoping to just use KiCad because of it’s bigger library. It looks like it’s not that simple.

I’m trying to short cut things by only covering what I need, but there is so much to this electronics thing that one thing leads to another and you end up having to learn everything.

I’ll have to look up “parametric footprint generators” and “courtyard layer”, because I don’t know what they are yet.

It’s a small Open Source Arduino based engine management computer called Speeduino. The brief is an EMS control that cost no more than $100.

http://speeduino.com/wiki/index.php/Speeduino

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This bloke here (@Marvin_Miller) has got the same ‘problem’… read the thread and follow my advice in there.

especially this post (don’t want to repost):

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The schematic default libraries include “Atmel”
This has the symbol “ATMEGA2560-A”
You can find a TQFP-100 footprint here http://smisioto.no-ip.org/elettronica/kicad/kicad-en.htm

The part you need is in SMD ICs, LQFP packages (25/01/2015) - Footprints
3D Modules

Be careful to use the correct 0.5mm pitch footprint

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A parametric footprint generator helps you generate simple pattern footprints where you got a lot of pads to position, size and set up to be of the kind you want.
It will have options for QFN, QFP, SSOP, SOP, etc. pp.
You just tell it what size the pads are (X x Y), the pitch, the row spacing, package dimensions, and so on… and it will generate the footprint for you.
Usually you then need to add some more information to the footprint in the footprint editor to match it to what you want in a footprint (extra REF field or different silk screen drawing), and it’s ready to go.

Personally I’ve never used one and don’t intend to, as the kicad_mod file format for footprints is human readable in a text editor and I can create QFN/etc. coordinate strings in excel :wink:

As for courtyard layer…
A layer in KiCAD PCBnew is a drawing layer - you remember clear overhead projector sheets that you could stack over each other? - same thing, just digital.
In PCBnew you got several of those layers, each has got a use. There is Front Copper, There is Back Soldermask, there is User Drawings… etc…
Two of them are the Courtyard layers… one for back and one for front. They are there to draw some bigger outline of devices on to (0.25 mm or somesuch, read link below), so that when you arrange them in PCBnew (with this layer switched visible - only time you need it) you place them in such a way that it is possible for a pick & place machine to do it in real, without crashing one device into another during placement (tolerances, tolerances, tolerances).
There are rules for the Courtyard layer (and all the other stuff for the Libraries and Repos), that you can read up on here:

In the end the layers are there to create the gerber files to make your board at a fab house.

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I’d encourage you to keep going. I went through the same thing two years ago and made my first board in CAD (ExpressPCB) and it worked very well. My second revision was also done in ExpressPCB and it’s virtually perfect. I really can’t think of anything I would do differently on that one (it was way more mature and feature-packed). I’m now on my 3rd revision and had wanted to use KiCAD back on revision 2 but finally made the change for version 3 (I needed something more mainstream).

I had zero IC/electronics experience, am still lacking in many fundamentals, but man, I’m on a tear and it’s been a lot of fun. You’d be really shocked how complex my boards are getting but I’ve been doing it bit by bit. Revision 1 was the real “I have no idea if this will work” experiment and it did. It still works to this day. When I did revision 2.0, it was so much more complex that I was still thinking, ‘Man, I hope I got this right’ - turns out I nailed it. Rev 3 is 1000x more complex but I’m not getting to the part where I have a lot of confidence. On the other hand, there’s a lot more to 3 and the more complex they get…the more the chance something might slip by.

These days it’s not too costly to do 4 proto boards so even if the worst happens, it ain’t the end of the world. Even so, I routinely spent one full week (literally) checking everything before going production. I’m going to be very interested in how KiCAD effects my workflow once I get to that point. Lots of great help in this forum too. In fact, I’ve found most electronics folks are very, very good at sharing/helping, much more so then in many other speciality venues.

Good luck with your board and don’t get discouraged! There’s lots of good videos on KiCAD as well (as mentioned in the other thread linked above).

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The drop in price amazes me. I have gone paying about 5k for layout and prototyping two layer boards by tape on lightbox 35 years ago. The PCB contractor drove a Lotus.
This was followed by using Redac Visula running on high end Sun workstations. As the hardware and software cost so much, only dedicated layout technicians were allowed near them.
Now I can use Kicad to get equivalent boards and get them made locally for about UKP50 including tooling

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Every organization I have ever worked in, that did board design or layout, maintained its own libraries of component symbols and footprints. There are at least a dozen valid reasons for doing so, starting with the one you mentioned: There may be errors in the libraries supplied by the program vendors.

Whenever I lay out a board I expect to spend anywhere from 20% to 80% of the total effort doing “library work”. At one place I worked, the PCB design team scheduled half a day each week just to correct, adjust, modify, and refine the existing libraries - in addition to library work that was required for specific projects.

Dale

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I don’t have 20 years experience in electronics, I have 4 months. I’m a Mech Eng, machinist, fabricator, and race engine designer that specialises in airflow that has only assembled 3 shop bought kits decades ago.

Because I knew nothing about electronics, and you can’t just buy a Speeduino to assemble with instructions - which I can do -, you have to learn every little step in the electronics field.

I had to read the Speeduino forum front to back, learn drawing in GIMP, learn Arduino, learn Fritzing, learn Fritzing part creation from scratch - there was no instructions for new part creation nor help until I wrote them -, learn Inkscape, learn XML, learn DIY home PCB production(toner, Riston), learn that there was small run PCB production houses, learn that there are major electronics supply warehouses, learn eBay/Paypal - never had to buy online before -, learn how electronic components work, learn the many flavours of EFI and different sensor requirements from different manufactures, learn about GitHub, learn about Gerber, learn SMT, learn SMT soldering techniques at home, learn about oscilloscopes, learn CadSoft EAGLE PCB, and who know what else, and now KiCad.

Out of everything I have just listed, I had never even heard of any of them 4 months ago except GIMP - I didn’t know the drawing part though -.

In Fritzing the silkscreen is the outline, so you use it so that parts don’t overlap - I’ve read enough posts where people are bending parts to fit after the fact -. People with unlimited budgets don’t have this problem, but when you are packing many through hole parts on a limited 100x100 broad for a price break, those outlines are crucial.

The MPX4250AP outline is missing, which would help in part placement. I made a new FZ part for the guy designing the boards so it will be easier for him.
https://raw.githubusercontent.com/noisymime/speeduino/master/reference/wiki/v0_4_board_annotated_1.jpg

The drawing suite in KiCad looks pretty simple - maybe too simple now that I’m used to Inkscape - so I could probably draw the part, but why duplicate work that has already been done. Plus if the part is already there it attracts more users because it makes the program easier to use for beginners. Thanks for the link to parts - I’ll figure the libraries out -.

You have a nice forum with lots of help, even if some posts talk down to you because you are a beginner, because the Fritzing forum is dead with nearly no help. I became the part creation expert over there, and I don’t really know what I’m doing.

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Outlines help, like this one I made that is accurate to hundreds of a mm.

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I find it is easy to forget what it was like before knowing stuff. So it can be difficult for experts to imagine what it is like for a beginner. Nowadays people like quick results, and the internet helps a lot. When I started there was just library books and a notepad. But there is really no shortcut to learning, it just takes time. I’ve found that I can pick up new things over time, but I don’t expect quick results.

Now that I know how, I find drawing symbols no harder than drawing the schematic, plus I get to draw it to my own preferences rather than other persons wacky ideas. The disappointment of not having a comprehensive library is long gone, and in practice I find that I don’t actually need to create many new symbols.

One little trick for checking placement is to print the PCB onto paper, then stuff the real component onto the paper. This is not completely accurate, but cheap to do. Placing components down to 0.1mm clearance can be problematic when suppliers change dimensions slightly or you choose different suppliers.

I admit I know little about ECUs. But it seems to me that to pack more components on a board, SMT components would be an advantage?

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Amen to that! I do the same but in Google Docs spreadsheet.