U490{1,2,3} diagrams

[Álvaro Lopes]

Werner Almesberger wrote:
> 
> I haven't added them to the expanded sheet yet because of the naming
> issue below.

Yes, perfectly understandable.

>> U4903: SN74LVC2G126
> 
> One small problem here: the enable signals shouldn't be inverted.
> 

You're definitely right. I wonder how I missed that. :/

Updated version in attach.

>> In schematics I have for GTA02, U4902 does not include SN prefix.
>> I also think (since these might be provided by different manufacturers)
>> we should avoid using the prefix on U4903 and U4901 too.
> 
> I thought about this for a while. It's very tricky. For example, the
> sn74lvc126 comes in packages with 5 or 6 pins/pads/balls. The differ
> in how they assign pin numbers. Now, TI only have 5 pin packages in
> production, so the SN is in fact a correct qualifier. NXP have 6 pin
> packages as well, so there you'd have to use another qualifier.
> 
> Perhaps we should call it 74126_5 and the other would be 74126_6 ?

I assume you meant 74AUP1G00 :)

Well:

The symbol is the same, however the device is different - the extra 6th pin is NC. KiCad does not seem to handle symbol/component differently as opposed to
eagle, for example.

Can't we add the extra NC pin on the footprint ? Maybe DRC will issue some warnings/errors though.

Anyway we can add some hidden pin if needed, and use that naming convention. Again, since we're mostly using openmoko components (I assume no manufacturer
changes from latest GTA02) we can just add the prefix and, if we need to change to some other component/outline, we add another prefix as well.

Álvaro

> 
> Thanks a lot !
> 
> - Werner

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