Restriction of autorouter?

Telemachus wrote on Mon, 15 February 2010 13:04

I'm still pretty new to Eagle. I've made a few PCB's so far, and

they've

turned out great, but I hadn't used the autoroute function at all until

 

now. I need some advice.

 

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the

digital signals, is there a way to restrict the autorouter such that it

 

does not mess with my already routed measurement circuitry?

Hello Brian,

Of course, you could do your own experiments to determine this--just backup

the files first.

But to answer your question, the auto-router doesn't touch anything that

was routed before it starts.  So if you hand-route power and critical

traces then it won't touch that stuff.

This is generally good but sometimes if you pushed a critical route just a

bit one way or the other you can fit one more trace through but the

auto-router needs to add a via and things get way congested very quickly.

So be careful where you put your critical routes.  Your first pass of the

auto-router may simple to figure out where congestion is going to occur and

then go back to original design (copy of design before auto-router was run)

and adjust critical traces accordingly.

Cheers,

James.

--

James Morrison  ~~~  Stratford Digital

email:  james@eaglecentral.ca

web: http://www.eaglecentral.ca

Specializing in CadSoft EAGLE

• Online Sales to North America

• Electronic Design Services

• EAGLE Enterprise Toolkit

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca

James,

Ok, thanks for the advice. Is there literature out there that goes over

the "art of autorouting" in Eagle or anything?

What I've ended up doing so far is to route the simple digital stuff,

most of the analog measurement circuitry, and the power lines, but then

divided my board into the parts that I've routed and those that haven't

using the "restrict" layers. It seems to have worked: I ran the

autorouter and it routed the complicated digital signals that would have

taken me forever.

However, I guess I should clarify what I mean by "touching" the analog

circuitry that I've already routed. For all intents and purposes, the

circuitry that I've routed is perfect, but it wasn't to the autorouter

because it looks to end traces smack-dab in the middle of SMD pads.

Since I've got a mix of packages, it added all of these crazy angular

traces, which I have to go back and delete now. Is there any way to stop

the router from doing this?

Regards,

Brian

On 2/15/2010 1:12 PM, James Morrison wrote:

Telemachus wrote on Mon, 15 February 2010 13:04

I'm still pretty new to Eagle. I've made a few PCB's so far, and

they've turned out great, but I hadn't used the autoroute function at

all until

 

now. I need some advice.

 

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

Hello Brian,

 

Of course, you could do your own experiments to determine this--just backup

the files first.

 

But to answer your question, the auto-router doesn't touch anything that

was routed before it starts. So if you hand-route power and critical

traces then it won't touch that stuff.

 

This is generally good but sometimes if you pushed a critical route just a

bit one way or the other you can fit one more trace through but the

auto-router needs to add a via and things get way congested very

quickly. So be careful where you put your critical routes. Your first

pass of the

auto-router may simple to figure out where congestion is going to occur and

then go back to original design (copy of design before auto-router was run)

and adjust critical traces accordingly.

 

Cheers,

 

James.

 

On 2/15/2010 1:12 PM, James Morrison wrote:

Telemachus wrote on Mon, 15 February 2010 13:04

I'm still pretty new to Eagle. I've made a few PCB's so far, and

they've turned out great, but I hadn't used the autoroute function at

all until

 

now. I need some advice.

 

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

Hello Brian,

 

Of course, you could do your own experiments to determine this--just backup

the files first.

 

But to answer your question, the auto-router doesn't touch anything that

was routed before it starts. So if you hand-route power and critical

traces then it won't touch that stuff.

 

This is generally good but sometimes if you pushed a critical route just a

bit one way or the other you can fit one more trace through but the

auto-router needs to add a via and things get way congested very

quickly. So be careful where you put your critical routes. Your first

pass of the

auto-router may simple to figure out where congestion is going to occur and

then go back to original design (copy of design before auto-router was run)

and adjust critical traces accordingly.

 

Cheers,

 

James.

 

James,

One other thing: what do net classes have to do with the autorouter? Can

these be used to route only certain classes of signals?

Regards,

Brian

Quote:

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the

digital signals, is there a way to restrict the autorouter such that it

 

does not mess with my already routed measurement circuitry?

As James already said, the autorouter leaves alone anything already routed

before you run it.  You may want to put polygons in tRestrict, bRestrict,

and vRestrict in specific places to keep the auto router from running new

tracks thru your analog section.

Quote:

For all intents and purposes, the circuitry that I've routed is

perfect, but it wasn't to the autorouter because it looks to end traces

smack-dab in the middle of SMD pads.  Since I've got a mix of packages,

it added all of these crazy angular traces, which I have to go back and

delete now. Is there any way to stop the router from doing this?

Yes, don't leave dangling ends.  Route your own traces to the middle of the

pads and you won't have a problem.  You should have had a bunch of airwires

indicating that Eagle thought the connections weren't complete.  If you got

wierd angles, then you must have left the ends fairly far from the pad

centers.  Don't do that.  As long as you get them close, the remaining

route will all be within the pad and not change the resulting copper.  It's

really not that hard to do it right though, and that way Eagle knows for

sure the connection is made.

Quote:

what do net classes have to do with the autorouter?

HELP CLASS.

Quote:

Can these be used to route only certain classes of signals?

I don't think so.  The point is to tell the autorouter parameters for the

tracks it creates.

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca

Olin,

Yes, that's well and good to look in the help, except that I don't find

the help article on this particularly helpful. What is the purpose of

specifying net classes? What are they used for?

Regards,

Brian

On 2/16/2010 11:23 AM, Olin Lathrop wrote:

Quote:

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

As James already said, the autorouter leaves alone anything already routed

before you run it. You may want to put polygons in tRestrict, bRestrict,

and vRestrict in specific places to keep the auto router from running new

tracks thru your analog section.

 

Quote:

For all intents and purposes, the circuitry that I've routed is

perfect, but it wasn't to the autorouter because it looks to end traces

smack-dab in the middle of SMD pads. Since I've got a mix of packages,

it added all of these crazy angular traces, which I have to go back and

delete now. Is there any way to stop the router from doing this?

 

Yes, don't leave dangling ends. Route your own traces to the middle of the

pads and you won't have a problem. You should have had a bunch of airwires

indicating that Eagle thought the connections weren't complete. If you got

wierd angles, then you must have left the ends fairly far from the pad

centers. Don't do that. As long as you get them close, the remaining

route will all be within the pad and not change the resulting copper. It's

really not that hard to do it right though, and that way Eagle knows for

sure the connection is made.

 

Quote:

what do net classes have to do with the autorouter?

 

HELP CLASS.

 

Quote:

Can these be used to route only certain classes of signals?

 

I don't think so. The point is to tell the autorouter parameters for the

tracks it creates.

The net classes allow you to specify different track sizes and spacings for

different nets.

This is used by DRC and the autorouter.

"Brian Zuelke" <brian.zuelke@ndcpower.com> wrote in message

news:hleoki$t9o$1@cheetah.cadsoft.de...

Olin,

 

Yes, that's well and good to look in the help, except that I don't find

the help article on this particularly helpful. What is the purpose of

specifying net classes? What are they used for?

 

Regards,

Brian

 

On 2/16/2010 11:23 AM, Olin Lathrop wrote:

Quote:

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

As James already said, the autorouter leaves alone anything already

routed

before you run it. You may want to put polygons in tRestrict, bRestrict,

and vRestrict in specific places to keep the auto router from running new

tracks thru your analog section.

 

Quote:

For all intents and purposes, the circuitry that I've routed is

perfect, but it wasn't to the autorouter because it looks to end traces

smack-dab in the middle of SMD pads. Since I've got a mix of packages,

it added all of these crazy angular traces, which I have to go back and

delete now. Is there any way to stop the router from doing this?

 

Yes, don't leave dangling ends. Route your own traces to the middle of

the

pads and you won't have a problem. You should have had a bunch of

airwires

indicating that Eagle thought the connections weren't complete. If you

got

wierd angles, then you must have left the ends fairly far from the pad

centers. Don't do that. As long as you get them close, the remaining

route will all be within the pad and not change the resulting copper.

It's

really not that hard to do it right though, and that way Eagle knows for

sure the connection is made.

 

Quote:

what do net classes have to do with the autorouter?

 

HELP CLASS.

 

Quote:

Can these be used to route only certain classes of signals?

 

I don't think so. The point is to tell the autorouter parameters for the

tracks it creates.

Telemachus wrote on Tue, 16 February 2010 13:37

Olin,

 

Yes, that's well and good to look in the help, except that I don't find

 

the help article on this particularly helpful. What is the purpose of

specifying net classes? What are they used for?

As Doug already mentioned, they are used by the DRC and auto-router.

For more info about the auto-router see the online help for the "auto"

command.  You can have it route a list of signals only.  But you can't give

it a net class to complete, although I agree that could be useful.

Also take a look at the auto-router section of the manual.  There is some

useful info in there.  If you don't have a printed manual there is a copy

in the /doc of the install directory.

Cheers,

James.

--

James Morrison  ~~~  Stratford Digital

email:  james@eaglecentral.ca

web: http://www.eaglecentral.ca

Specializing in CadSoft EAGLE

• Online Sales to North America

• Electronic Design Services

• EAGLE Enterprise Toolkit

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca

Telemachus wrote on Mon, 15 February 2010 22:06

James,

 

Ok, thanks for the advice. Is there literature out there that goes over

 

the "art of autorouting" in Eagle or anything?

The best way is to sit down and play with it to get a feel for how it

behaves and what the parameters do.  There is a useful section of the

manual that explains all the parameters and their ranges.

Quote:

What I've ended up doing so far is to route the simple digital stuff,

most of the analog measurement circuitry, and the power lines, but then

 

divided my board into the parts that I've routed and those that haven't

 

using the "restrict" layers. It seems to have worked: I ran the

autorouter and it routed the complicated digital signals that would

have

taken me forever.

That's a good way to use it.

Quote:

However, I guess I should clarify what I mean by "touching" the analog

 

circuitry that I've already routed. For all intents and purposes, the

circuitry that I've routed is perfect, but it wasn't to the autorouter

 

because it looks to end traces smack-dab in the middle of SMD pads.

Since I've got a mix of packages, it added all of these crazy angular

traces, which I have to go back and delete now. Is there any way to

stop

the router from doing this?

Yes and no.  You can use the command line to have the auto-router ignore

certain signals or to only route certain signals.  See "help auto" for more

info.  Note, wildcards can be used.

But you really want to connect the final ends of those traces.  The

ratsnest will report traces unrouted until they are all gone.  And you

don't want to risk missing one that actually is not routed because you have

100 that are almost routed.

EAGLE 5 now has magnetic snap for the last segment to the center of the

pads/smds so it's much nicer than it used to be.  So make use of that and

route it right to the connection point.  If you finish a net EAGLE will

beep at you so you know it's done.

Cheers,

James.

--

James Morrison  ~~~  Stratford Digital

email:  james@eaglecentral.ca

web: http://www.eaglecentral.ca

Specializing in CadSoft EAGLE

• Online Sales to North America

• Electronic Design Services

• EAGLE Enterprise Toolkit

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca