Following on from the addition of delay tuning earlier in the development cycle (see Post-V9 New Features and Development News - #15 by JamesJ ), the last piece of that puzzle is now in place. Introducting Tuning Profiles:
Tuning Profiles are configured in their panel in the Board Setup dialog, and then assigned to Net Classes in the Net Classes panel. They allow the definition of per-layer parameters for routing which requires more constraints than those offered by net classes alone. Each tuning profile can define per-layer track geometries (for single-ended or differential signals), per-layer track propagation speeds for time-domain tuning, and specific via overrides for delay calcluations that have had external calculation or simulation of via properties. Different overrides can be specified based on via start / end layers, and signal start / end layers, allowing specific handling of blind vias and other such via technologies.
The track geometry parameters (width / diff pair gap) can be calculated automatically for a target impedance, and specific signal and reference layers (microstrip or stripline, single-ended or differential, are automatically handled from the reference layers and Tuning Profile type settings). These calculations use the existing KiCad PCB calculator tools, and take the stackup information (dielectric heights, dielectric constants etc) from the defined board stackup. To run the calculations, ensure a target impedance is defined and click on the ‘refresh’ button in each Width or Gap grid cell. For differential pairs, the other parameter needs to be specified by the user (e.g. width must be specified if calculating diff pair gap). In all cases, the propagation delay will be calculated and updated. For manually entered track parameters, the delay can be calculated from those manually entered values by clicking the refresh button in the delay cells.
All parameters can also just be entered by hand if external field solvers or PCB fab geometries are being used. No target impedance is required in these cases.
There are two configurable options for each Tuning Profile - Generate Net Class DRC Rules and Enable Time Domain Tuning. If Generate Net Class DRC Rules is selected, width / diff pair gap rules are automatically generated, for use when routing across multiple layers requiring different geometries:
If Enable Time Domain Tuning is selected, track parameters for statistics and length / skew tuning can use the time domain tuning and DRC constraints previously implemented:
Please note that due to the changes required in the underlying storage to support this workflow, if you had previously manually entered time domain parameters these will not be migrated. Please ensure you record those parameters before opening the project for re-entry in this new method.
