Board DRC - Supposed to Generate Errors/Warnings on Unrouted Nets?

On 09/10/10 20:56, Michael Sansom wrote:

I just noticed that I have two unrouted nets on my board layout (i.e.

the ratsnets lines are visible but no copper tracks connect) and the DRC

isn't generating any errors/warning.  Is this correct?  What am I doing

wrong, I've never seen a DRC that wouldn't flag unrouted signals.

If the DRC were to warn about unrouted signals, it would ave to

run a complete RATSNEST (including processing all polygons) every

time the DRC is run. Clearly this is not desirable.

Klaus Schmidinger

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Klaus Schmidinger                       Phone: +49-8635-6989-10

CadSoft Computer GmbH                   Fax:   +49-8635-6989-40

Pleidolfweg 15                          Email:   kls@cadsoft.de

D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de

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On 9/13/2010 2:38 AM, Klaus Schmidinger wrote:

On 09/10/10 20:56, Michael Sansom wrote:

>> I just noticed that I have two unrouted nets on my board layout (i.e.

>> the ratsnets lines are visible but no copper tracks connect) and the DRC

>> isn't generating any errors/warning.  Is this correct?  What am I doing

>> wrong, I've never seen a DRC that wouldn't flag unrouted signals.

>

If the DRC were to warn about unrouted signals, it would ave to

run a complete RATSNEST (including processing all polygons) every

time the DRC is run. Clearly this is not desirable.

>

Klaus Schmidinger

You say that Clearly this is not desirable, but I think you are somewhat

hasty with that declaration.  Clearly other PCB layout packages do check

for unconnected nets during the DRC.  Also, your engine is pretty fast

at processing polygons, so I suspect that Eagle doing a RATSNEST during

a DRC is still probably going to be faster than your competition (I know

you would be faster than Allegro).

In the end, I'm fine with doing a RATNEST outside of the DRC, though it

is not what new Eagle users moving over from other tools are going to

expect.

That said, if I were you I'd really think about adding a feature that

lets you quickly locate unconnected nets on the layout after you run the

RATNEST command.  I know now that there is a ULP that helps with this,

but in my opinion this functionality is generally expected to be

integrated in the software as it ships.  Before I was told that a ULP

existed for this function I was reduced to turning off all layers except

the Unrouted layer and turning off grid dots just to see these small

no connects.

On 9/13/2010 2:38 AM, Klaus Schmidinger wrote:

On 09/10/10 20:56, Michael Sansom wrote:

>> I just noticed that I have two unrouted nets on my board layout (i.e.

>> the ratsnets lines are visible but no copper tracks connect) and the DRC

>> isn't generating any errors/warning.  Is this correct?  What am I doing

>> wrong, I've never seen a DRC that wouldn't flag unrouted signals.

>

If the DRC were to warn about unrouted signals, it would ave to

run a complete RATSNEST (including processing all polygons) every

time the DRC is run. Clearly this is not desirable.

>

Klaus Schmidinger

You say that Clearly this is not desirable, but I think you are somewhat

hasty with that declaration.  Clearly other PCB layout packages do check

for unconnected nets during the DRC.  Also, your engine is pretty fast

at processing polygons, so I suspect that Eagle doing a RATSNEST during

a DRC is still probably going to be faster than your competition (I know

you would be faster than Allegro).

In the end, I'm fine with doing a RATNEST outside of the DRC, though it

is not what new Eagle users moving over from other tools are going to

expect.

That said, if I were you I'd really think about adding a feature that

lets you quickly locate unconnected nets on the layout after you run the

RATNEST command.  I know now that there is a ULP that helps with this,

but in my opinion this functionality is generally expected to be

integrated in the software as it ships.  Before I was told that a ULP

existed for this function I was reduced to turning off all layers except

the Unrouted layer and turning off grid dots just to see these small

no connects.

Let me add one final thing.

Clearly you could add a check box to the DRC options that says "Check

for unrouted nets".  You've got several options for the DRC

configuration as it stands now and this one would fit nicely under the

"Misc" tab.  That way your user could decide if checking for unrouted

nets was something that he wanted to do in the DRC or not.  If a

customer thought that checking for unrouted nets was slowing down his

DRC too much, he could uncheck this option and it would work as it does

now.  However if the customer was accustomed to having the DRC check for

unrouted nets, this would give him the option to continue to do so in

Eagle as well.

-Michael