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Author Topic: arduino digital pin spacing  (Read 1548 times)
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hey all,

i'm creating a stepper driver shield for (fr/ar)duino, and i've noticed that the digital pins are spaced strangely.  i'm wondering if anyone could answer a few questions:

1. what is the exact spacing, in mils? (this is my most important question.)
2. what is the reason for a non-standard spacing?
3. are there any plans to change this in the future?  if so, it should be done sooner rather than later.  (like pulling a bandaid off, the faster you do it, the sooner the pain is gone.)

thanks,
Zach Smith
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the wierd spacing is an enduring mystery
if you're using eagle, you can grab my protoshield layout and just delete everything you dont want smiley
http://www.ladyada.net/make/pshield

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cool, thanks.

one question:  i'm doing this in Eagle, so how do i take your .brd file, and load it up with my schematic stuff, all while preserving the pin spacing?  this part is a real mystery to me.
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open up my sch/brd and then delete all the parts that arent header
then copy & paste in your schematic.
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i measured it in Eagle: 155 mils.

i still havent quite figured out how to move/copy/paste stuff in eagle, and i have a large design that wires into all of the digital pins, so i'd rather not re-wire that.

ps. i figured out how to measure stuff with the 'Mark' tool, then you look to the top where it will tell you the distance between the points.  not the greatest UI, but what can ya do!
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Zach, to be able to do cut/copy/paste, you need to open all the files using the same control panel.  From source brd file, group the elements you want to copy, copy them and switch to the other brd window and paste.
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Quote
i measured it in Eagle: 155 mils.

i still havent quite figured out how to move/copy/paste stuff in eagle, and i have a large design that wires into all of the digital pins, so i'd rather not re-wire that.

ps. i figured out how to measure stuff with the 'Mark' tool, then you look to the top where it will tell you the distance between the points.  not the greatest UI, but what can ya do!
You can create the headers, then set the grid to 155 mils and move one of the headers so it is 155 mils apart from the other header.
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I'm not sure why that spacing is the way it is.  It's not likely to change though; we considered it for the Diecimila, but decided against it because not only would it have created incompatibilities with existing shields, but you would have needed different shield for the BT boards.  It sucks, but there are ways to work around it if you're using perf-board: bending pins attached to the perf-board, or using wires instead of pins.
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well, i guess now that i know the exact distance its cool... that type of info would be great on the 'shields' page on the arduino site.
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Zach, I think the separation is exactly 150 mils, not 155.  The standard separation between pins in the header is 2.54 mm or 100 mils.  The separation between the 2 digital headers is 2.54 mm + 1.27 mm = 3.81 mm = 150 mils.
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Don't forget you can move things to absolute coordinates with Eagle.
From top to bottom, coordinates in Mils,  left to right, we have:

Move 'J3' (1287.205 2000.717)
Move 'J1' (2147.079 1999.079)
Move 'POWER' (1550 100)
Move 'J2' (2251.197 101.079)

(interesting that the vertical alignment is slightly off too.  These measurements from the "reference" board designs arduino_rs232_v23.brd AND arduino_usb_v2.brd off the arduino website.)
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I also had difficulties trying to find the grid specification in the schematics... it is almost impossible to modify the original schematics! (I am not an Eagle expert).
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