Re: gEDA-user: Open Collector Error Checking

[Colin D Bennett <colin@xxxxxxxxxxx>]

On Thu, 10 Feb 2011 16:47:39 -0700
John Doty <jpd@xxxxxxxxx> wrote:

> 
> On Feb 10, 2011, at 4:40 PM, Oliver King-Smith wrote:
> 
> >   I am getting this error when I run the DRC2
> >   ERROR: Pin(s) with pintype 'open collector': U70:2 U70:4
> >       are connected by net 'unnamed_net204'
> >       to pin(s) with pintype 'open collector': U70:2 U70:4
> >   The above statement is absolutely correct, these two pins are
> > both open collector, and indeed they are wire together.  But why
> > would I want to report this as an error?  Isn't part of the idea
> > behind open_collector outputs the concept of wiring them together?
> 
> Oliver, drc2 is a deeply flawed program. It reports many, many
> perfectly reasonable things as errors. That doesn't make it useless:
> by sifting through all the crud you'll find real problems. But assume
> that most warnings it emits are wrong.

I agree with Oliver that the essence of open collector signals is to in
fact allow multiple drivers of the line to share it!  Thus this drc
message is particularly annoying.

However, I do find running the gnetlist drc useful to find bonehead
errors like forgetting to connect a certain "input port" symbol to the
corresponding "output port" symbol, or typos in the net names of such
symbols, etc.  It's too bad that it has so many flaws, I guess, since
it has the potential of being a very powerful tool.

Regards,
Colin


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