kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

On 9/15/2016 2:47 PM, Chris Pavlina wrote:
> On Thu, Sep 15, 2016 at 06:54:59PM +0100, Dan Weatherill wrote:
>>     Hi all,
>>     I've been using kicad for about 5 years. Recently (mostly with CERN
>> changes - especially differential pair support), it's become suitable for
>> more and more of my more complex projects (I'm switching from Altium
>> Designer). I also have about 10 years experience working on c++ projects,
>> but am not what you would call an "expert".
>>     A feature I've been especially missing in Kicad for several projects is
>> something akin to Altium's "harnesses": that is, basically a "bus-like"
>> entity which contains named signals, possibly of different types (e.g.
>> input, output, passive etc). Harnesses are very useful for drawing things
>> like e.g. SPI, I2C, CAN connections which have well defined named signals.
>> Harnesses contain better information than numbered busses for this
>> application, but can help with schematic "overcrowd" when wiring up chips
>> with many signals such as micros, FPGAs etc. This is often a big problem
>> especially in hierarchical designs where to do this using wires requires
>> possibly dozens of hierarchical labels.
> 
> I _really_ want this. IIRC I submitted a wishlist item for it ages ago,
> and nothing ever really became of it (and as usual I ran out of time to
> implement it myself). These are hugely useful in complicated designs.
> 
>> I've been thinking about implementing this for a while, but have not started
>> due to being aware that eeschema is under fairly major re-factoring at
>> present.
>>
>>     With guidance from c4758p on #kicad, I think that this feature could be
>> implemented with the following steps:
> 
> For anyone who doesn't know yet, I'm c4757p on #kicad, or c4758p when my
> connection's dodgy ;)

So your the guy who's been raking me over the coals on irc. ;)

> 
>> 1) add two new items in NETLIST_ITEM_T enum, likely called NET_HARNESS and
>> NET_HARNESSLABELMEMBER, which have similar functionality to NET_BUS and
>> NET_BUSLABELMEMBER but for harnesses
>> 2) several changes to connection rules in netlist.cpp (most majorly in
>> pointToPointConnect() and a new function
>> NETLIST_OBJECT_LIST::connectHarnessLabels() )
>>
>> 3) minor UI additions (harnesses can be just a different colour wire, and
>> harness-to-wire connections at this time can be just the same as wire-to-Bus
>> connections)
> 
> In light of the proposal to add line color support to eeschema, I'd like
> to see something different than just a color. They look like this in
> Altium:
> 
> http://techdocs.altium.com/sites/default/files/wiki_attachments/231555/Harness+Connector+with+entries.png
> 
> A point wrt. UI is that when eeschema is converted to GAL, a good bit of
> the UI code will need to be ported or thrown out. I don't think that
> should necessarily stall development, but I'd warn you to be prepared
> and write your code to be properly modular and easy to port. :)
> 
>>
>> The main question usability wise would be how to label harnesses. I see two
>> possible options:
>> 1) new syntax: a harness has a label using new type of brackets, with
>> harness type in brackets, e.g. an I2C bus called A would be "A{I2C}". The
>> wires would be then labelled exactly like bus labels, e.g.: "A[SCL], A[SDA]"
>>
>> 2) bus-like syntax: using same brackets as bus syntax, but make a harness
>> when the contained type is a string rather than numbers, i.e. "A[I2C]" for
>> harness label, "A[SCL], A[SDA]" for harness members.
> 
> I haven't given this a huge amount of thought yet. Does anybody see a
> reason for this to me more than just a stylistic detail? We discussed
> this a bit on IRC and concluded that it would matter if harnesses were a
> subclass of buses, but if they're a separate object I don't think so.
> 
>>
>>
>> I guess there are implications for the schematic file system which I need to
>> understand, and need to be discussed.
> 
> As far as I can see, we just need to add a 'harness' type similar to the
> 'bus' type.
> 
>>
>> All suggestions welcome, and I hope to start working on this soon.
>> Thanks,
>> Dan W
>>
>>
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