Arduino shield adafruit.lbr layout (package) bugs

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ericwertz
 
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Arduino shield adafruit.lbr layout (package) bugs

Post by ericwertz »

I decided to start with the Arduino shield footprints in adafruit.lbr (because it was already in my "lbr" directory) and found that they have at least two problems. All four Arduino* layouts ("packages") are affected.

The first problem is that the spacing between the D0-7 and D8-13 headers is not 160 mils as it's supposed to be -- it's at least 5 mils off one way or the other.

The second problem is that none of the headers are on-grid (normally 50mil or 100mil for most people). All of the 6/8-pin headers are off-grid by 15 or 20 mil depending on which header it is. I found this problem by simply looking at the layout and noticing that not a single header lined-up. All should be on-grid, except the infamous, wonky PORTB header.

It looks like what happened is that the entire board layout was shifted 20mil (0.02") to the right, and then the left edge pulled back out to make the board corner align at the grid origin, and then the D8-13 got boned-up somehow -- but not necessarily in that order.

The net result is that shields are 0.02" wider (to the left) than the boards below them, and that the one set of digital headers is off, probably making for a marginally snugger fit (for better or worse). Most impacted are probably Eagle users who don't find that any of their traces line-up.

The best remedy would probably be to slide everything to the left by 0.02", and leave the left edge in negative X space (if that overhang needs to be preserved for some reason), and then fix the placement of the PORTB header, relative to the PORTD header.

adafruit
 
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Re: Arduino shield adafruit.lbr layout (package) bugs

Post by adafruit »

we'll try to download the Uno layout and check this out. it -does- work but yeah it might be a little off!

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westfw
 
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Re: Arduino shield adafruit.lbr layout (package) bugs

Post by westfw »

It's worth noting that the pin 7-8 spacing has in fact been inconsistent between different versions of arduino.
On the diecimila and earlier, the spacing is 0.16 inches.
On the Ardunio Mega, the spacing was 0.15 inches. No one noticed.
On the initial Uno boards and in the initial Uno Reference design, the spacing was 0.15 inches. People noticed and complained as part of a general "Uno quality sucks" thread (http://www.arduino.cc/cgi-bin/yabb2/YaB ... 5887736/47 ), and the reference design was quickly fixed to 0.16 inches again. I'm not sure what happened with the production line; the differences is "obvious but not very important" if you hold a Uno next to a Diecimila.

Having none of the connectors be "on grid" in the shield "part" is a separate and relatively cosmetic issue, IMO. In any complex part it is always an interesting question just where the origin should be...

adafruit
 
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Re: Arduino shield adafruit.lbr layout (package) bugs

Post by adafruit »

we now follow whatever the Uno reference up on the site is

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