[Milkymist-devel] rotate J21 ?
werner at almesberger.net
Sat Jan 28 08:37:31 PST 2012
When working on the ledm board, I realized that the orientation
of J21 is a little confusing:
In the schematics, it's drawn with 5V/3V3 at the top and ground
at the bottom, which is a fairly common way of showing things.
Now, in the PCB layout, the "top" of J21 is close to the edge
of the PCB and the bottom points towards the middle of the PCB.
When working on an extension board, it would seem intuitive to
me to consider the extension board area to be located at the
lower side of the M1. That's simply because it's more
conveninent to work on something nearby instead of having to
reach across the whole M1.
Now, this creates the problem that J21 is reversed in relation
to the schematics, which can easily lead to confusion and fried
What shall we do ?
0) Do nothing to schematics or layout. Just show it rotated or
maybe in both views in the documentation.
1) Rotate in the schematics (and the documentation). Leave the
layout as it is.
2) Rotate in the layout and leave the schematics as they are.
Rotating in the layout would be the most intrusive change and
it would break compatibility between rc2/rc3 and >= r4 more
than anything else. If we ever want to make this sort of
change, it's probably no or never, since post r4, the installed
base should simply be too large. (Or so we fervently hope ;-)
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