How much do you trust your CAD Program?

Question

OK, I just have to vent a bit.I am laying out a board with an XC9536.  The schematic capture program I am using is a major program, not some fly by night outfit.  They claim their component library is done by an ISO 9000 organization.So my perfectionist tendencies didn't like the fact that they used a different font for the pin names on the XC9536 schematic symbol than they usually do in the libraries.  I went into the "Library Executive" to change the font and when I went to save the part the program told me that the pin numbers in the component pin list didn't match what was entered into the schematic capture symbol.So I checked the XC9536 data sheet and found out that their pin numbers for the schematic symbol were ALL WRONG.  I had to spend about half an hour relabeling all the pins, and then moving things around to make it look nice again.So if I hadn't decided to change that font, I could have done a board layout with all the pins connected wrong.I'm starting to think it would be better if board layout programs just shipped with no pre-made components.  I just end up fixing things on nearly every single part I use anyway.  Sometimes I think it would be better if I just did it all myself.

Antti Lukats · Accepted Answer

"Carl Smith" schrieb im Newsbeitrag news: snipped-for-privacy@news.west.earthlink.net...

my trust in CAD programs to be accurate is: 0%

the schematic libraries are wrong the PCB components pads are wrong, etc..

always check ALL pin mapping in schematic libs, and the PCB symbols as well, you may end up re-doing both of them !!

after having a wrong PCB symbol in PADS i never ever again trust blindly any pre-made CAD library components

Leon · Answer

Incorrect footprints can also be very annoying, that has caught me outonce or twice.Leon

Hal Murray · Answer

I never trust anything direct from the vendor library.

I keep my own set of libraries. When I need a new part, I often start with pieces I find in the vendor libraries, but everything gets checked. It's generally sane to get a friend to double check things. It's too easy to fool yourself.

Most of the time, you can do a layer of sanity checking at the board layout stage. You wired signal-foo up to pin

98 because it's in the top right corner... or you swapped signals foo and bar because that made the board easier to route.

After they have been used on a board with no problems I become more trusting.

Hal Murray · Answer

My straw man is to print the gerber layer out 1:1 and see if thepart fits cleanly.You may have to tweak the scale factor to get things to printat the right size.  Check the board outline with a ruler or somethinglike that.-- The  mail server is located in California.  So are all myother mailboxes.  Please do not send unsolicited bulk e-mail or unsolicitedcommercial e-mail to my  address or any of my other addresses.These are my opinions, not necessarily my employer's.  I hate spam.

Nial Stewart · Answer

If I need a new component I don't even check to see if it's available, I do it myself and get it reviewed. That way you know it's definitely right (probably).

Nial

------------------------------------------------------------- Nial Stewart Developments Ltd FPGA and High Speed Digital Design

formatting link

Noway2 · Answer

I agree, my trust in the pre packaged libraries is 0%.  I always use adatasheet and enter the symbol and footprint patterns and then I liketo double check it the part against a 1:1 print.

Sylvain Munaut · Answer

I remember once creating a part my self, then discover after I get thePCB that I didn't unzoom the PDF enough ... i missed the fine print atthe bottom that said "bottom view" ...	Sylvain

How much do you trust your CAD Program?

Join the Discussion

Didn't find your answer?