Re: gEDA-user: Schematic Level DRC DIscussion

[Steven Michalske <smichalske@xxxxxxxxx>]

>>
>>>
>>>> From my reading of DRC2 it tests for
>>>
>>> 1) Non numbered parts
>>> 2) Duplicate references
>>
>> But, of course, some of us often use multiple symbols for one part.
>>
>
> I do as well, I have added to my code an attribute that tells the
> netlister to not include this sybol in the bom. In essence, I am  
> saying
> that this symbol is part of a collection of symbols and that this
> particular symbol isn't the one that provides the bom info. So it  
> could
> also be a clue to a drc that it shouldn't be judged to be a duplicate
> part.
>

as i see this,  adding attributes for multi-graphic symbols,  there  
should be a X of Y attribute.  the DRC then could warn or error on a  
missing X in the sequence of the Y in a particular refdes.

4 symbols make a part

refdes=U1A
multiOF=4
multiPart=1

refdes=U1B
multiOF=4
multiPart=2

refdes=U1C
multiOF=4
multiPart=3

refdes=U2D
multiOF=4
multiPart=4


The drc checker would then complain that
U1 is missing 1 of 4 parts: 4
U2 is missing 3 of 4 parts: 1, 2, 3

>
>>> 3) One connection nets
>>
>> That's somewhat useful. But it also complains of unconnected pins,
>> which are normal, not usually errors.
>>
>>> 4) net pin types
>>
>> Using a classification nearly irrelevant to anything except pure
>> digital design.
>>
>>> 5) slots
>>> 6) duplicated slots
>>> 7) un-used slots
>>>
>>> I would expect complaints about duplicate slots and un-used slots.
>>
>> Unused connector pins are extremely common in error-free designs. And
>> I think it adds clarity to treat connectors as multi-slot rather than
>> having a lot of named lines converging on a big block.
>
> Mater of personal preference that I woun't argue about. But then we
> should have a way of surpressing drc warnings or errors for this  
> type of
> slotted device. no_unused_slot_drc=true # opt out not opt in
>

i propose that DRC be more of a plugin approach.
Having a config file for your design that enables what plugins you  
want to enable.
also a DRC waiver attribute for the symbols.

i would like to have a check that tests if a 2 pin component has the  
same net on both sides of the component.  this normally is a  
problem,  but i have placed resistors that i have shorted out so that  
i can place a resistor there by cutting the trace and placing the  
part,  in this case attaching a DRC waiver to the part is needed.

>>
>>> Not
>>> about the way the pins are hooked together. One obvious weakness is
>>> that
>>> the test schematic connects, V+, V-, VL and GND together. These are
>>> all
>>> type pwr and thus according to the matrix they may be connected. I
>>> think
>>> this is a weakness of pins not being heavier.
>>
>> Yes, but how to fix. Making the pins heavier will make symbol
>> construction even harder for new users. Pin classification is already
>> confusing.
>>
>
> I am in favior of heavier pins. I think that devices should have a way
> of saying. Hey a Vcc power pin for this device should only be  
> connected
> to nets that have 3.3V. This would have possibly prevented one flipped
> power level for a subcircuit on a recent board. Pop goes the
> tantalims ;)
>
> One reason pin classification is so hard is that there is no  
> attempt to
> limit attributes to any type of object and that the value of an
> attribute can be anything.
>
> A smarter attribute system that says net segments can have this   
> list of
> attributes and each of these attributes gets a list of legal values.
> Then the selction method would restrict users to reasonable values.
>

I feel that the unbounded attribute system has allowed great  
flexibility,  but I can see having more standard attributes, with  
ranges and enumerations specified.  all of my symbols i make get a  
Mouser and Digikey field,  for obvious reasons.

Steve



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