There is a weakness how Eagle grabs the end of an airwire. Look at the
attached img simplified to represent a chained flyby address signal of a
ddr ram.
The red layer is terminated to TP1, so when I click the airwire at TP1,
I expect it to grab the green layer, but if my current active layer is
closer to the red layer, it will grab the red wire. It would perform at
best if a loose wire end took priority over a terminated end.
This is causing me some grief.
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On 17.08.2016 12:09, Rachael wrote:
Hi Morten,
It took me a second to work out what you were getting at but once I did I
realised I have come across this exact problem several times and it's
really quite frustrating as it's fiddly to work around.
I found I had to put in a temporary via in between the two locations I was
trying to connect, placed directly in the path where the trace would go, to
give the air wire somewhere else to go to and hitting ratsnest, and then
routing from that in both directions. Then once the trace was correctly
routed I removed the via. It's fiddly as hell and can sap time if you have
to do this a lot (like for an entire DDR bus!).
I like your suggestion of making the loose end have priority over the
terminated end of the air wire, I think this would solve the problem but I
am unsure if there would be any unintended consequences of this, that would
have to be thoroughly tested I think. Maybe having a way of toggling the
start of the route to the other end of the air wire (or scrolling through
several if it went off in multiple directions) would be another way to do
it.
Just to build the case, I just bumped into another same-issue case.. See
attachment.
I just came in with the purple wire and stopped at the point where I
want to set via and wire back to J8 on the blue layer. Instead of the
relative long process of clicking middle button + picking the bottom
layer on the long 16 layer list, I stopped there, and wanted to pick up
the airwire from J8 pad and shift click on the tip of the purple wire to
complete the net (much easier). But instead of starting from blue layer
pad J8, eagle started from purple layer above J8, creating a
junction/stub on purple layer and preventing me to do what I wanted.
It selected purple, because that was my current layer, and hence
closest, not the most logical.
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