1. Home
  2. Field-Programmable Gate Arrays
  3. How much do you trust your CAD Program?

How much do you trust your CAD Program?

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.

Reply to
Carl Smith
Loading thread data ...

"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

--
Antti Lukats
http://www.xilant.com
Reply to
Antti Lukats

Incorrect footprints can also be very annoying, that has caught me out once or twice.

Leon

Reply to
Leon

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.

--
The suespammers.org mail server is located in California.  So are all my
other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.
Reply to
Hal Murray

My straw man is to print the gerber layer out 1:1 and see if the part fits cleanly.

You may have to tweak the scale factor to get things to print at the right size. Check the board outline with a ruler or something like that.

--
The suespammers.org mail server is located in California.  So are all my
other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.
Reply to
Hal Murray

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

Reply to
Nial Stewart

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

Reply to
Noway2

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

Sylvain

Reply to
Sylvain Munaut

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.