Re: [Kicad-developers] Diff pair clearances
Hi Wayne, > On 18 Sep 2018, at 23:20, Wayne Stambaugh wrote: > > On 9/18/2018 7:20 AM, Jeff Young wrote: >> When calculating obstacles we currently use the diff-pair gap as a >> clearance between a diff-pair trace and a diff-pair pad. >> >> I’m pretty sure that’s wrong. I’m just not sure how wrong. >> >> I suspect the diff-pair gap shouldn’t be used as a clearance /at all/. >> It’s the gap between the traces, not a clearance. > > Why wouldn't you use the netclass clearance or the default netclass > clearance if a netclass is not defined? It seems to me that the gap has > nothing to do with the clearances other than the gap between the diff > pair traces. Yes, that is indeed our conclusion. I just wanted to make sure I wasn’t missing anything as the code was using the gap as a clearance. Cheers, Jeff.___ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
Re: [Kicad-developers] Diff pair clearances
On 9/18/2018 7:20 AM, Jeff Young wrote: > When calculating obstacles we currently use the diff-pair gap as a > clearance between a diff-pair trace and a diff-pair pad. > > I’m pretty sure that’s wrong. I’m just not sure how wrong. > > I suspect the diff-pair gap shouldn’t be used as a clearance /at all/. > It’s the gap between the traces, not a clearance. Why wouldn't you use the netclass clearance or the default netclass clearance if a netclass is not defined? It seems to me that the gap has nothing to do with the clearances other than the gap between the diff pair traces. > > But maybe we should consider it a clearance between two /tracks/ of a > diff-pair. This would allow you to manually route each wire. But if > you do that, should we consider it a diff-pair or not? (Even if we use > the gap as a clearance, it’s only going to enforce minimum distance; it > won’t keep the tracks gap-width apart. And I imagine you won’t be able > to tune it. So I’m not sure it’s really a diff-pair.) > > Thoughts? > > Cheers, > Jeff. > > https://bugs.launchpad.net/kicad/+bug/1789690 > > ___ > Mailing list: https://launchpad.net/~kicad-developers > Post to : kicad-developers@lists.launchpad.net > Unsubscribe : https://launchpad.net/~kicad-developers > More help : https://help.launchpad.net/ListHelp > ___ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
Re: [Kicad-developers] Diff pair clearances
Agreed. Diff pairs should have an associated clearance rule to other objects and it has nothing to do with the gap. One place where the gap should be used is in manual tuning of the pair. If I route a pair and end it on a component that necessarily has non-symmetric pad fanout, I might want to move one of the diff pair tracks and not the other. The gap is then the clearance used to the other track when considering it for PnS. On Tue, Sep 18, 2018, 07:20 Jeff Young wrote: > When calculating obstacles we currently use the diff-pair gap as a > clearance between a diff-pair trace and a diff-pair pad. > > I’m pretty sure that’s wrong. I’m just not sure how wrong. > > I suspect the diff-pair gap shouldn’t be used as a clearance *at all*. > It’s the gap between the traces, not a clearance. > > But maybe we should consider it a clearance between two *tracks* of a > diff-pair. This would allow you to manually route each wire. But if you > do that, should we consider it a diff-pair or not? (Even if we use the gap > as a clearance, it’s only going to enforce minimum distance; it won’t keep > the tracks gap-width apart. And I imagine you won’t be able to tune it. > So I’m not sure it’s really a diff-pair.) > > Thoughts? > > Cheers, > Jeff. > > https://bugs.launchpad.net/kicad/+bug/1789690 > ___ > Mailing list: https://launchpad.net/~kicad-developers > Post to : kicad-developers@lists.launchpad.net > Unsubscribe : https://launchpad.net/~kicad-developers > More help : https://help.launchpad.net/ListHelp > ___ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
