Feature Request / Routing Failure: Layer swaps not supported for multi-point nets

[MenashayAu]

I am using KiCadRoutingTools on a dense 4-layer ESP32 board and encountered a routing failure due to a current limitation with multi-point nets.

When attempting to route an I2C bus (/I2C_SDA) that connects 5 pads, the router was unable to complete the path. Because the net connects more than 2 points, the plugin disabled layer swapping (vias) for this net, forcing it to try and find a continuous 61mm path entirely on a single layer, which failed after 410,000 iterations.

Relevant Log Snippet:
Using 2 routing layers: ['F.Cu', 'B.Cu']
WARNING: Skipping layer swaps for 1 multi-point net(s) (not yet supported)

• /I2C_SDA
  ...
  [1/1] Routing /I2C_SDA (id=25)
  Detected multi-point net with 5 pads (Phase 1: main route only)
  Multi-point net Phase 1: routing longest MST edge (pads 1 and 4, length=61.36mm)
  No route found after 200000 iterations (forward), trying backward...
  Failed to route farthest pair after 410000 iterations
  FAILED: Could not find route (0.22s)

Feature Request:
It would be incredibly helpful to have layer swapping (via placement) supported for multi-point nets in a future release. Currently, this limitation requires users to manually route all buses (I2C, SPI, etc.) that connect to more than two components on dense boards.

Thank you for your work on this tool!

[drandyhaas]

Layer swapping here means the ability to change the layer of pre-existing bga or qfn stubs. Multipoint nets have no limitations about using vias or doing normal layer changes during routing. Your net simply could not find a route for some other reason. Try increasing the max iterations limit? Maybe something else is blocking?
However, as the warning message is misleading, I'll work on removing it when no stubs exist for the net.

[drandyhaas]

Fixed in commit 409d53e:

• The warning is now suppressed when all stubs on a multi-point net are already on the same layer (no stub layer swapping would have been possible anyway, so the message was misleading)
• Clarified the warning text to say "Skipping stub layer swapping" instead of "Skipping layer swaps"

[drandyhaas]

If the original poster could do a git pull (on the main branch) and check that the warning message is gone in this case, and report here, it would be appreciated.