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

[mskala at northcoastsynthesis.com]

On Mon, 13 May 2024, Donald Tillman wrote:

> To be clear... I said "publication quality".  And by that I mean, worthy
> of a graphic you would see in a textbook.  We have a long history of
> electronics textbooks with elegant schematic diagrams.  As someone who

As you're surely aware, the "schematic capture" part of a CAD suite has
another function beyond making a visually appealing diagram:  it is
creating the input for the PCB design software, electrical rules checker,
BOM generator, and so on.  What's being created is really more of a
database than a schematic diagram at all, and the schematic shown on the
screen is just a view of the database.  There's tension between creating
the prettiest picture and creating a correct database in minimum work
time, and it's understandable that the designers of the software may not
make the tradeoff in favour of visual appearance every time.

There's also a strong element of user choice:  most people doing schematic
capture are primarily interested in going on to the next stages of PCB
design, manufacturing, and so on.  So they may make trade-off decisions
like using a ready-made symbol from a library that isn't ideal but gets
the message across, because drawing a nicer one would be a lot of work and
wouldn't provide any important benefit to them.

Kicad output from someone who knew what they were doing and who was
specifically focused on making a good-looking diagram, might be
better-looking than Kicad output intended purely for the functional
purpose of feeding the PCB design program.  But someone who had the goal
of a pretty picture probably would be using drawing software instead of
any schematic capture software.  It's called schematic "capture" for a
reason:  the underlying assumption is that you have your schematic
already, which you drew with something else (like a pen!), and now you're
just entering it into the machine so the CAD software can work with it.

Saying "publication quality" may not be the best standard given that when
one really looks hard at them, most publication schematics are *actually
bad*.  The standard should be the best publications, or what we wish
publications could be; not necessarily what most publications really are
in practice.

The schematics of my own with whose appearance I've been happiest, have
been the ones I made in LaTeX with the Circuit_macros package.  That isn't
schematic capture software and it doesn't generate input that would be of
any use to CAD software.  It is *only* for drawing the pictures.  And it's
too cumbersome for any but the smallest circuits.  I wouldn't care to use
that for the circuit of an entire synth module unless someone was paying
me to do so, with more money than I can plausibly get just by selling
modules.

I use Circuit_macros for many of the small schematics in documentation of
my commercial modules; but whole-module schematics, and large clips from
them, are done with Kicad to save time and readers just have to suck that
up.  They're as good as the schematics other companies have published for
their products for the last several decades, and these days, customers
rightly consider themselves lucky to get a schematic at all.

> gEDA gschem allows me to export to PostScript or PDF, and it handles the

I wrote off gEDA after I found that it would reverse the anode and cathode
of diodes between schematic and board by default, and I was rudely treated
on the relevant mailing list when I suggested that that wasn't an ideal
way for it to operate.  But if you're only using it to draw the schematic,
then electrical correctness of the data going to the PCB software doesn't
matter.

-- 
Matthew Skala
North Coast Synthesis Ltd.