kicad-developers team mailing list archive

[Evan Shultz <evan.shultz@xxxxxxxxx>]

Since other ECAD tools are specifically mentioned and I use a new tool I'll
add my 2 cents. I'm a Cadence Design Entry HDL user (oh God, it's so
awful...) working with always hierarchical schematics often having >100
pages.

DEHDL works on a principle where you add symbols and then they're
'packaged' (annotated) later. That part is like KiCad. Each symbol has a
property where the ref des is the property value. The property can be set
to locked or not (this is determined by having a leading dollar sign or
not). If the user manually types in a ref des, it automatically locks and
the ref des cannot be changed during annotation. The user can also manually
lock a property after annotation.

A cool feature is the 'ref des pattern' which is applied during
'packaging'. Packaging happens from the top down, and as the packager moves
deeper and deeper into the schematic it pushes down into from the top. If I
have a hier block with any random property, let's say BLOCK_SUFFIX, I can
then use the value of that property in the 'ref des pattern'. For example,
if I have 8 instances of the same block I can give them a BLOCK_SUFFIX
property with a value A through H. Then the ref des pattern can be '<symbol
prefix><incremented number starting at 1><BLOCK_SUFFIX>' where <symbol
prefix> is 'R' for resistor, 'C' for capacitor, etc. and controlled by the
library symbol. So I will get a R1A in the first block. And the
corresponding part in the second block is R1B, continuing on through R1H.
For parts at the top level of the schematic not in a block, or parts in a
block without a BLOCK_SUFFIX property, the value is automatically set to an
empty string. And any sub-blocks will also get the same BLOCK_SUFFIX from
their parent block. I could also make a pattern like  '<symbol
prefix><DESIGN_SECTION><incremented number starting at 1><BLOCK_SUFFIX>'
where DESIGN_SECTION is a property on blocks broken up by function in the
product so '1' for digital circuitry, '2' for analog, etc. This means the
first resistor in the digital part would be R11, and the first resistor in
the analog circuitry is R21A going through R21H. And if I put I/O
connectors at the top level of the schematic, I get J1 and not J11. There
are many, many uses and that is one thing I think fits nicely with the core
idea proposed that I'd love to see in KiCad.

One painful step is that any block which is to have multiple instances and
be packaged like I've shown above must be packaged on it's own. Not in the
scope of the entire design, but with the block itself as the top level of
the schematic. Then later that block (and any child blocks) can be packaged
with the entire schematic. There are a number of hoops to jump through and
potential gotchas if the you want the BLOCK_SUFFIX behavior described above
to work.

If a user in DEHDL places too many gates to fit into one physical package
and then have locked the ref des, there is an error during packaging and
packaging stops. It knows if have the power pins of an opamp set to be U73,
and I place another set of power pins also set to be U73, that cannot work.
But if a user places a bunch of symbols the packager will try to condense
them into as few physical packages as possible (there are several settings
but that's the default behavior). I personally would like to be aware of
what's going on during this step of annotation and not see KiCad create 43
physical parts on it's own simply because of how I decided to construct the
schematic without having any options.

Regarding multi-unit symbols spread around a schematic, in DEHDL one can
place a symbol in a block but not have that symbol packaged with other
symbols in another block, whether the blocks are peers or parent/child. For
example, if I have one dual opamp gate in one block and another in another
block, I will get two physical packages. DEHDL can't handle that situation.
It's a little sad. The workaround would be to add ports and place the
common part at a high level in a schematic. Imagine a dual instrumentation
amp circuit with a block containing a pair of inst amp blocks. The single
gain setting resistor would need ports if a single dual pot or dual
digitally-controlled resistor IC or other single component is to control
the gain of both inst amp circuits. Make sense?

DEHDL can add parts to a BOM without them having a schematic
representation, but it's a horrible process that I've tried several times
and given up on. It feels like the kind of thing that an Intel or Motorola
paid $1B to have implemented and it's tied to one user's specific way of
working and their library structure. I can see value in the idea, but not
the execution.

Lastly, when pushing schematic changes to a board in Allegro the parts go
into a queue and can be placed in many ways. They can be placed manually,
one-by-one, but there is an autop-placement feature that gives many
options. One is to place at a selected point by schematic page so I can
plop down piles of footprints that represent each schematic sheet. And then
I can do the layout once and replicate it for multiple corresponding piles.
I really like having more control over placing footprints than Pcbnew
gives, but alas. I'm not sure this was already part of the discussion
above, so sorry if it's a tangent.

I'd be happy to answer questions or provide screenshots if that helps to
explain things. Let me know.

Cheers!

On Thu, May 7, 2020 at 3:54 PM James Jackson <james.a.f.jackson.2@xxxxxxxxx>
wrote:

> Thanks Jon - I don't have access to Altium so that's really helpful.
>
> I was wondering about the possibility of locking components; I sometimes
> want to do this with, for example, key ICs - MCUs, DACs, etc. One could add
> this as a Symbol Property, which wouldn't need any changes to file formats.
> Whether it got a custom checkbox in the Symbol Properties dialog, or would
> just be there as another option that a user may add (which would make it a
> 'power user' feature as it wouldn't be obvious unless one knew to add it)
> would need to be considered - UI clutter vs. access to features for all.
>
> With the multi-part consideration, where on the schematic does it dump the
> new components? It wouldn't be too difficult to implement an algorithm
> which finds a space in which all the sub-components required could fit,
> with some gross assumptions on layout. Or can Altium add a component to the
> BOM without it being on the schematic?
>
> I'm also mindful that some algorithms can't solve everything (although
> this strikes me as a non-trivial problem, rather than an impossible
> problem...) - and bailing out and telling the user why is also always a
> option, in the spirit of 'do no harm'.
>
> Yours,
> James.
>
> On Thu, May 7, 2020 at 9:59 PM Jon Evans <jon@xxxxxxxxxxxxx> wrote:
>
>> Altium doesn't have "annotate selected"
>> It does let you lock the annotation on components at will, so you can
>> lock some, reset everything (which ignores locked) and then re-annotate.
>> If you change the annotation of one part of a multi-part component, it
>> will result in two components being forwarded to the PCB like Janvi
>> proposes.
>> And also likewise, the ERC will warn about this if configured
>> appropriately.
>>
>> As to how it handles the complex hierarchy situations JP mentioned, I'm
>> not certain to be honest, because Altium's hierarchy model is a bit
>> different from KiCad's (in some ways simpler) and I haven't checked to see
>> if the same situations are possible.
>>
>> -Jon
>>
>> On Thu, May 7, 2020 at 4:48 PM James Jackson <
>> james.a.f.jackson.2@xxxxxxxxx> wrote:
>>
>>> That's an interesting take on it. I can foresee the catastrophic
>>> addition of loads of other components though, if there's an error in the
>>> schematic somewhere and a rogue missing / one-over unit gets cascaded down
>>> sheets.
>>>
>>> What do other EDA tools do with annotation? Do they have this feature?
>>> Do they handle these conditions?
>>>
>>> On Thu, May 7, 2020 at 8:18 PM janvi@xxxxxxxxx <janvi@xxxxxxxxx> wrote:
>>>
>>>> > - What about multi-units components: for instance what about renaming
>>>> 2 of 5 units when one unit is the unit handling the power pins?
>>>> > this is the best way to break a design.
>>>>
>>>> This should add another component to the BOM and schematic DRC should
>>>> report unused gates for both of the reference designators
>>>>
>>>> > Good luck with block annotation.
>>>>
>>>>
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