Author Topic: Symbol + Footprint = Component Question  (Read 3383 times)

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Offline spudboy488

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Symbol + Footprint = Component Question
« on: March 04, 2016, 12:11:23 am »
I  really want to like KiCad but, at this point, I can't get past the current work flow. I've read all the pros on it already. What I am looking for is the ability to build a preferred part library. Most CAD packages I've looked at allowed building a library by tying a schematic symbol to a footprint, adding various information such as vendor, vendor part number, and other basic BOM stuff, and then saving it in a library as a component. For example, the PIC18F46K22 symbol is tied to a 44-TQFP footprint with the Digikey part number of PIC18F46K22T-I/PTCT-ND and stored in the library as PIC18F46K22T-I/PT. Since this is my processor of choice, I would be able to pull it from the library and use it in my design knowing that the footprint and ordering info is correct. Has anybody found a way to implement what I described?

For me, the lone engineer that does schematic, layout, component purchase, and assembly, I require certain things to make my job a bit easier to maintain. I know up front what components I plan to use because I tend to use what I have in stock. New parts are built into library components, ordered, and put into inventory.
 

Offline ElektroQuark

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Re: Symbol + Footprint = Component Question
« Reply #1 on: March 04, 2016, 12:17:48 am »
It can be done. You can set the footprint for the symbol in its properties and add a custom field with the vendor part number.

In my own KiCad library I use that system so each symbol has its embedded footprint and datasheet link. All of them are unique components.

Offline jolshefsky

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Re: Symbol + Footprint = Component Question
« Reply #2 on: March 04, 2016, 12:36:53 am »
I  really want to like KiCad but, at this point, I can't get past the current work flow. I've read all the pros on it already.

I use it too and it is often quite frustrating. I kind of expected it when the top selling points were free, unlimited, and open-source ... Usual rules apply: "cost, time, features—pick one, adjust the other, and let the third go."

What I am looking for is the ability to build a preferred part library. Most CAD packages I've looked at allowed building a library by tying a schematic symbol to a footprint, adding various information such as vendor, vendor part number, and other basic BOM stuff, and then saving it in a library as a component. For example, the PIC18F46K22 symbol is tied to a 44-TQFP footprint with the Digikey part number of PIC18F46K22T-I/PTCT-ND and stored in the library as PIC18F46K22T-I/PT. Since this is my processor of choice, I would be able to pull it from the library and use it in my design knowing that the footprint and ordering info is correct. Has anybody found a way to implement what I described?

While I haven't done anything with the BOM capabilities (if there are any worthwhile, I don't know), I do know you can hint CVPCB (the schematic-to-board part mapper) to use specific footprints. In the EESCHEMA's library editor, in a part's options screen, select the "Footprint filter". The asterisk (*) is the generic zero-or-more wildcard, so for your specific example, you could add "44-TQFP" but I'd typically add "*44*TQFP*" in case I have other packages that sort-of match (e.g. it would also suggest "44TQFP-rev. B").

For what it's worth, given my past as a computer programmer, I appreciate that I can edit the text-based files myself if I want to get something done special. Positioning a lot of pins is often easier to do for me with a spreadsheet and text editor than with the clunky GUI ... and I can do things not available in the GUI like to make a part with drawings/text on layers other than top/bottom silkscreen (e.g. Drawing or Comments). I have a Python script to generate a BOM and a pick-and-place file, but I will be giving the GUI a shot soon enough. In no way do I think this will sway anyone toward KiCad, but it's useful to me.
May your deeds return to you tenfold.
 

Offline nctnico

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Re: Symbol + Footprint = Component Question
« Reply #3 on: March 04, 2016, 12:45:40 am »
It can be done. You can set the footprint for the symbol in its properties and add a custom field with the vendor part number.
But that way you can't re-use a symbol and you'd have to copy the same symbol many times for a similar component. Think about resistors and capacitors.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline ElektroQuark

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Re: Symbol + Footprint = Component Question
« Reply #4 on: March 04, 2016, 12:49:09 am »
That's not a problem for me.
I don't use a 1K resistor, I use MFR-25FRF52-1K (for example), with all of its characteristics well defined.

Offline nctnico

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Re: Symbol + Footprint = Component Question
« Reply #5 on: March 04, 2016, 12:59:29 am »
That's not a problem for me.
I don't use a 1K resistor, I use MFR-25FRF52-1K (for example), with all of its characteristics well defined.
But how do you change the symbol for all resistors?
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline spudboy488

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Re: Symbol + Footprint = Component Question
« Reply #6 on: March 04, 2016, 03:58:13 am »
It can be done. You can set the footprint for the symbol in its properties and add a custom field with the vendor part number.
But that way you can't re-use a symbol and you'd have to copy the same symbol many times for a similar component. Think about resistors and capacitors.

This is one of my biggest gripes. Other CAD packages allow you to marry a common symbol to a common footprint and store it as a unique part. You would have 1 resistor symbol tied to 1 footprint, say a 1206 SM, add some BOM info and save it as a 1K, for example. Modify the BOM of the 1K part and save it as a 1.2K part (using the same symbol and footprint but just changing the BOM part number). You can then do this for the entire inventory of 1206 resistors using a single symbol and single footprint.

DesignsparkPCB does this and, IMHO, is one of the easiest systems to build a library with. I have all my preferred symbols in 1 file. I have all my preferred footprints in another. My married components are in a 3rd. This third library is the one that is used during the design and layout.
 

Offline stryker

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Re: Symbol + Footprint = Component Question
« Reply #7 on: March 04, 2016, 08:59:54 am »
I moved from Eagle to KiCad cold turkey just over a year ago.  While I can see both ways have merit, on balance I prefer the flexibility of the KiCad way, and having one symbol reused for all footprints.  There are other niggles I have with KiCad - this isn't in the top 5.  But I remember my frustrations with Eagle too.

I have also enjoyed how easy it has been to migrate from through hole to SMT in the past year without changing any schematics, just reassiginging footprints and respinning the boards.  But then there's the downside of the KiCad way as you can (and I have) assign an incorrect footprint with for example, pins reversed in a MOSFET. 

It will be interesting to see what direction the devs take with this aspect of KiCad.

 

Offline nctnico

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Re: Symbol + Footprint = Component Question
« Reply #8 on: March 04, 2016, 09:27:47 am »
It will be interesting to see what direction the devs take with this aspect of KiCad.
I hope they see the light and make it possible to have a database with components where a component points to a schematic symbol and a footprint. Such a setup is mandatory is a professional workflow because it is a huge time saver in many ways. I have been working like this with Orcad for over 15 years now and I really don't want to get back to copying symbols and assigning values to each of them or use tools to guestimate the footprint for a symbol.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline spudboy488

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Re: Symbol + Footprint = Component Question
« Reply #9 on: March 04, 2016, 11:34:51 pm »
I hope they see the light and make it possible to have a database with components where a component points to a schematic symbol and a footprint. Such a setup is mandatory is a professional workflow because it is a huge time saver in many ways. I have been working like this with Orcad for over 15 years now and I really don't want to get back to copying symbols and assigning values to each of them or use tools to guestimate the footprint for a symbol.

Exactly!!
 


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