Pin-Layout - why the smaller gap?

[zimbosmurf]

Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins.

Since my first Arduino-Project I wonder who had the idea of this "glitch" in the pinlayout of almost any arduino-board? Obviously this was done on purpose - but what was the reason behind it? It makes it so difficult to use the arduino on a breadboard or another experimenting-board by just stacking it on top.

Don't be mad for me posting this "stupid" question - but I like to understand!

[karl_eller]

I second this. I'd love to be able to whack my Arduino in a breadboard upside-down using some header pins, but the uneven gap between Pins 7 and 8 makes this impossible. It does seem a little odd that they've (apparently deliberately) stopped us from doing this.

[CrossRoads]

Discussion from several years ago was that the design was rushed a little to make a deadline and the spacing was messed up by accident, and has since stuck.

[retrolefty]

Discussion from several years ago was that the design was rushed a little to make a deadline and the spacing was messed up by accident, and has since stuck.

Correct, it was an admitted error in their rush to market for their first boards. After that they were (and still are) reluctant to change it because it would make all existing shields incompatible then and now. So not a design choice, just an error not caught in time.

Lefty

[robtillaart]

I'd love to be able to whack my Arduino in a breadboard upside-down using some header pins

I have seen a pin kit or shield for that long time ago. - http://dangerousprototypes.com/2012/07/25/hack-fit-an-arduino-on-a-breadboard/ -

You might check on - shieldlist.org - if there is a shieldversion of it

furthermore you might check this - http://arduino.cc/en/Main/Standalone -

[Peter_I]

I agree in this being an annoying detail!

It could be solved by having an extra header on the inside of the misaligned header, but moved a bit to even out the misalignment.
In that way it would be easy to make your own shields from perf-board, and the existing shields would still fit.

[drjiohnsmith]

hi

the second header, is such an obvious idea,
   well done,

lets have it on all boards, PLEASE.

[WizenedEE]

lets have it on all boards, PLEASE.

No, that'd be confusing for people. Not that having two pins for PC4 and PC5 isn't confusing...

[ajk_]

Well, the design is open, there is nothing preventing you from rolling your own. The double row is an excellent idea, I like that one.
Also, it is fully possible that if you use the proper tool, you can bend that row over. I can't remember where, but you can buy them pre-bent.