kicad-developers team mailing list archive

[Dan Weatherill <dan.weatherill@xxxxxxxxxx>]

Dear all,
apologies for randomly jumping into this. When I switched from Altium Designer 
to kicad for most of my simpler designs (sometime in about 2013), the thing I 
missed most about Altium Designer's schematic editor was the "harness" 
feature, which in Altium are distinct from buses and are incredibly useful for 
things like SPI, I2C, USB, etc where there are logically named nets which are 
logically grouped. I even (briefly) discussed this on the list a few years ago 
and started on a very basic implementation which due to life issues never went 
anywhere. 

Jon's work appears to bring much of the usefulness of Altium Harnesses to 
kicad, and since I haven't seen that comparison mentioned in any of the 
discussion so far (apologies if I just missed it), I'd invite anyone who 
doesn't see the utility of this to look at a couple of videos about harnesses 
in Altium. 

I (hopefully) have some more time to work on open source projcts in the coming 
year, and hope to try and put some work in on the other feature I miss from 
Altium - back annotating components from the layout to the schematic. That's a 
discussion for another time though.

Thanks,
Dan W

On Tuesday, 19 December 2017 07:06:24 GMT Marco Ciampa wrote:
> Hi Jon,
> first of all, thanks for listening my thoughts.
> 
> I waited to send this letter a few days to wait for things to clear up to
> me. I think that this still apply although some things might be a little
> clearer now, so, in a way it is a little obsolete. I am sending it the same
> because I do not want to kill its spirit...
> 
> ...but please continue to keep in mind that these are my 0.00000000000002
> cents humble opinions...and really nothing more...
> 
> On Thu, Dec 14, 2017 at 08:21:29AM -0500, Jon Evans wrote:
> > Hi Marco,
> > 
> > The idea of aliases is to be "templates" for buses when you also give
> > names
> > to a bus.
> 
> Ok clear.
> 
> Let's call them templates then because for me an alias is just an alias.
> 
> > This is a little different than you describe, and I think is a
> > powerful feature.
> 
> I do not want to be unrespectful and ungrateful especially since I am not
> a dev but... there are many powerful features that we (actually you devs)
> can concoct but not all of them would probably turn out to be of such
> usefulness even if very powerful and feasible.
> 
> I think that we should always keep in mind a need to be fulfilled and
> some cases of use in witch such a feature turns out to be useful.
> 
> And even if it turns out to be of some usefulness, there is always a
> trade-off between an increase in complexity of the design process
> and benefits to the designer and in the complexity of the schematics.
> 
> If we are not able to find an example in witch this feature literally
> kills a big deal of work, then I am afraid that we are introducing some
> rarely used, obscure to grasp and difficult to document feature.
> 
> I mean that schematics are to be understood in printed form. The meaning
> (of the syntax) of the drawings should as of immediate comprehension as
> possible. Every template/macro/alias that we add to the schematics should
> probably:
> 
> 1) be documented in printed form (no, a pop-up window is not enough) on
>    the design sheets
> 2) must be easy to read (as in a paper print) even if you do not know
>    KiCad at all
> 
> because this feature, if I got it right, seems to me more a kind of
> "programming" than "describing" a circuit design
> 
> > If you define an alias called MEMORY, you can then define *multiple
> > different* memory buses, so they have to have different prefix names. But
> > you can also choose to use aliases *without* a prefix name, and then
> > everywhere you use that alias will be part of the same set of nets.
> > 
> > So, a more realistic and simple example would be:
> > 
> > Define alias "USB" containing "DP", "DM"
> 
> Ok
> 
> If I do not see this definition somewhere on the sheet, am I still able
> to understand the schematics just looking at a print on paper of it?
> 
> If I need to see also the "alias" definition to understand the
> schematics, where can I look at this template definition on the sheets?
> 
> > Now in one sheet you have a USB hub. You can define four different buses
> > with names and the alias, and get nets like "PORT1.DP" and so on.
> > 
> > But on a simpler design, you might not need four ports, so you can just
> > use
> > "{USB}" in your bus name and get nets without any prefix.
> 
> But it seems to me that this is the same name of a net on the bus with
> name "USB"...
> 
> > I think both options of how to use buses are valid and useful, and I also
> > understand your confusion when presented with all these options at once.
> 
> Would you be so kind to continue with this example and show how could be
> represented, for instance, a 4 USB bus schematic? Or other examples that
> could benefit from this feature?
> 
> I do not really "see" it if I haven't a real example to look at... it's
> my lack of imagination, I know...
> 
> > With that in mind, do you have any thoughts on how we could preserve the
> > power of this feature while making it easier to understand?
> 
> If we (you devs) find really worth, my suggestion is to:
> 
> 1) clearly divide the template/class definition from the istances syntax
>    (but I do not know how though...).
>    The confusion to me arises from this "all in one" approach.
> 
> 2) find a way to describe it "on paper" to make schematic sheets readable
>    to non KiCad users (normal elect. engineers)
> 
> My suggestion here is to keep it as simple, and clear, as possible.
> Between powefulness and readability, if it is not really worth it, I
> personally prefer the latter.
> 
> Best regards,