I have separated ground on my dual-layer PCB design into what is essentially signal and power ground. It’s an analog circuit and I would like to make a ground plane just for power (and use a star ground for signal) on its own layer without creating connections to ground from the signal layer. I haven’t used netclasses (maybe I should? How do I do that? I simply imported my schematic into the PCB editor) but is there a way to essentially force the ground plane to create ground connections only with the holes/pads connected to ground only on the layer it is on?
To do this, you have to separate the GND connections into two nets, (for example GND and AGND) and then connect those nets with a net tie.
I actually identified three grounds in the schematic: GNDPWR, GNDREF, GNDS. GNDREF is at 4.5V (half supply), GNDPWR and GNDS are at 0V. The PCB editor only recognises the former two.
The pcb editor must recognise all signals/nets. Maybe you have the 4.5 net with more than one label in the schematic
What do you mean? I am using KiCAD 7.
OK, I think I understand where the problem lies. GNDPWR and GNDS are connected together (they share a node). The PCB editor therefore ignores GNDS and connects everything to GNDPWR. The idea was that the PCB editor would correctly recognise that certain paths would be routed differently according to the power symbol. If I place a 0R resistor between GNDS and GNDPWR it correctly differentiates between the two. The problem is, I don’t really want to add a footprint that I don’t need. I have implemented a star ground and everything is fine as it is, the circuit is properly grounded and there are no pins to connect. If I fill B.Cu (where the power lines are) I should be able to essentially disregard the current ground lines while still excluding the signal ground lines from the ground plane.
KiCad does not “ingore” GNDS. It does add the pads of GNDS to the netlist. But when you connect two named nets to each other, then they get merged into one net, and KiCad can only use one name for a net, so it chooses a name. You can enable an ERC warning for this if you want.
Of course. When those nets are not connected together, they are two separate nets, each with their own name. But instead of a 0Ohm resistor, you can use a net tie. A net tie is also a footprint, but it only consists of pads and copper so there are no BOM items or assembly costs.
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