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I'm working on a board where I have a couple of optional headers to measure current. The idea is that the header will not be populated on every board, I can bypass it by closing a solder bridge, like that:

current measurement header

The problem is the following: On the left side 3V3 comes out of the regulator. This is a "Power" class net. It continues to the test point then to J5 header for current measurement and to JP3 bypass solder bridge. On the right side of these it is not net 3V3 anymore, it's a random blah, and with that move it has lost its class "Power". As you can see I have added this class again manually and named it VBL. I would prefer not doing any of that, I would like it to be the same net on both side oh the pin header. I also understand why it happens. But surely there is a solution to that.

Another reason for finding a solution: some further components (like TP4, or the connection going south from that, or the cap. on the right) are practically on the same net, as in from the circuit point of view it doesn't matter on which side they are connecting to. But when laying out a board it can make a big difference: if I find a really nice place for TP4 far right from all that, on the board design TP4 will be unhappy unless I connect it to the left side (which might be far away). It shouldn't actually matter.

So how do professional people deal with that? I use KiCad for all that btw...

Thanks for your attention!

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    \$\begingroup\$ Why don't you just select another standard power symbol? There are a number of power types available, (for example from: Menu - Place/Add Power/Power). Just use a unique name from the list, maybe use 3.3VP, 3.3VA, VPP, VDD, or another. That will become a new "Power" net, unconnected to the original 3V3. You will just connect it manually (with the solder bridge) when needed. \$\endgroup\$
    – Nedd
    Sep 23, 2023 at 2:15
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    \$\begingroup\$ There's a feature request on the KiCad bug tracker to add functionality for this sort of thing. \$\endgroup\$
    – Hearth
    Sep 23, 2023 at 3:15

2 Answers 2

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I understand that, for small schematics where all 3.3V connections are drawn, this is appealing.

But now, lets suppose you do a bigger project, over several pages, where you use 3.3V at many different places : usually, you no longer draw the 3.3V "wires" all over the place : you just use the 3V3 label all over the place, and let Kicad figure out that they are all connected.

But if before and after the jumper the net name is the same, how would Kicad know which components go before the jumper and which after (maybe you want to measure current for everything, maybe just the current going to a particular component, maybe to part of the components but not others, ...

Even if you stick to drawing all connections explicitly (which would be a big mess on a big project), which would make the schematics non ambiguous, when going to the routing stage, how would you/the auto-router know what to connect on which side if it is a single net?

What you can do, is duplicate the 3V3 net (sorry, I don't remember the exact way to do this, and I'm using my private computer where I don't have Kicad installed), and rename one of them to a meaning-full name (for example, I often use 3V3_PRE before the jumper/current measure resistance(shunt), and "3V3" after)

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  • \$\begingroup\$ Kicad don't know, just like it doesn't know where to place a bypass capacitor unless you add a net label. Components can be named too so you know where they belong. \$\endgroup\$
    – MiNiMe
    Sep 23, 2023 at 10:08
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In schematics place 3V3 on the right side of the jumpers too - or in PCB New- edit and change the "random blah" net to the 3V3 net. DRC will give an error about the solderpads being unconnected, that can be ignored.

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