pcb-rnd knowledge pool
Extended objects: bus
| extobj_bus by Tibor 'Igor2' Palinkas on 2020-03-08 | Tags: howto, extended, object, objects, extobj, line, bus, differential, pair, multi, track |
Abstract: Thje bus extended object is intended for simplify drawing bundles of evenly spaced parallel traces. The two main use cases are differential pairs and parallel buses.
The edit-object is a series of line objects (extobj::role=edit, on any layer). There can be multiple edit-objects. Parallel traces of fixed geometry at fixed pitch are rendered under each edit object on the target layer. Joints are properly handled as long as:
- the two edit objects are within the same bus extended object (thus extending the bus must be done by grabbing the endpoint of an edit line already part of the bus)
- the two edit lines share an endpoint precisely (this can be done using object snapping)
Note: junctions are not possible.
Extobj details:
- the edit-object is a cover line (thickness set by the tool to match final bus thickness), typically on a doc layer
- the extobj attribute should be bus
- pitch is set using extobj::pitch (coord)
- trace thickness and clearance set by extobj::thickness and extobj::clearance (coord)
- width (number of parallel traces) is set using extobj::width (integer)
When a cover line is converted into a bus, the following defaults are set up:
- width to 2
- trace thickness and clearance from the current drawing style
- pitch is set so the empty space between two parallel lines match clearance
- target layer is the current layer
An example/test board is available.
Demo video:
Steps shown in the video:
- 1. optional: create a new extobj layer group and layer. When done, this can be used to avoid the edit-object interfering with the board. By user convention the new layer group should be a global doc layer and the purpose should be 'extobj'.
- 2. draw the thick edit-line (actual thickness doesn't matter)
- 3. select it and use the menu or {s c e} to convert the line into an extended object
- 4. edit the geometry by grabbing the edit-object line or its endpoints; extend the bus by further segments by using line refraction and moving the endpoint of an existing edit-line; wireframe draw helps looking under the cover line
- 5. edit properties by right clicking on the 'E' mark
- 6. connecting the bus wires is as easy as just drawing traces to them
- 7. click any edit-line of the bus and the whole bus is selected; it can be then easily copied and the new bus can be edited independent of the original copy