[sdiy] What's the best freeware schematic capture and PCB layout software

[Tom Wiltshire]

Sorry, what the hell are screws doing in a schematic?!?

If that's how Kicad is intended to work, that's insane, but I doubt that. The BOM created by the software should include all the parts that go on the board, sure. But that doesn't include the mounting hardware or the enclosure or anything else. That's mechanical design at that point and there are other CAD packages for that job - make sure that what you're using can export data in a form that is compatible with what you're using for the other part of the process.

While this sounds very contrary to what Matthew is saying, I do have some sympathy for his view. I've also had circuits where I've drawn two different versions of the same thing, because (for example) I had a guitar stompbox circuit and I needed a diagram that showed the whole circuit including the external jack inputs and the effect in/out footswitch. You can do that on a schematic and show the switches and everything, but if you're designed a schematic to be turned into a PCB, those connections are just off-board links that don't tell you much ("connection1", "connection2" etc). So it *is* pretty easy to finish up with one version for "display" and one version for "manufacture", even with something as simple as a guitar pedal. Of course, you *can* work around this by adding non-netlisted graphics to the schematic that fill in the missing off-board components, but that *is* a fudge, and it is error-prone since there's no way to check those connections (and they're so often the ones people get wrong!).

Tom

> On 13 May 2024, at 20:25, Matthew Skala via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> On Mon, 13 May 2024, Donald Tillman wrote:
> 
>> I don't see a "tension" between a pretty diagram and a correct netlist.
>>  Features in one are not at the expense of the other.
> 
> Often they are.
> 
> For example, the "power flags" in many Kicad-generated schematics, which
> serve only to tell the electrical rule checker that a given net is a power
> net, are to the detriment of making the schematic look good.  I've also
> added things like screws to a schematic just to make them appear in the
> BOM, or mounting holes to make them appear and be properly linked to the
> right nets on the board, because that was more convenient than doing it
> any other way, even though I would not include these things in a schematic
> intended solely only for display purposes.  In the other direction, a
> schematic meant for humans to read would preferably include notes, voltage
> readings, waveforms, and so on, which may be difficult to add in a
> schematic capture program that only really has feature support for things
> that will affect the netlist because that's all it's designed to create.
> 
> When humans only have limited time, and time is money, the time they spend
> doing something that is useful for only one of the netlist or the printed
> diagram, is literally at the expense of the other.
> 
> There are also indirect ways in which the design or encouraged use of a
> CAD program can affect the appearance of the schematic, beyond the direct
> features of the program.  For instance, Kicad comes with a lot of
> third-party libraries and users expect to use those.  Some of the symbols
> in those libraries look bad; and others look okay by themselves but are
> drawn to a different scale from symbols in other libraries, so that two
> symbols from different libraries next to each other will clash.  And
> there's little incentive to spend developer resources on prettying up the
> symbols because these issues don't affect the netlist, which is the
> priority.  The developers made, and continue making, a choice about what
> their priorities are.
> 
> -- 
> Matthew Skala
> North Coast Synthesis Ltd.
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