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From the elinux.org documentation for this GPIO, I have summarized the following information:

The Raspberry Pi Model A+ and B+ boards, and the Pi 2 Model B, have a 40-pin 2.54 mm header marked J8, arranged as 2x20 pins. GPIO voltage levels are 3.3 V and are not 5 V tolerant. There is no over-voltage protection on the board - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board.

The header looks like this:

enter image description here

What I would like to do is create a breakout panel that provides, primarily, easy to access and labelled jumper lead sockets for the GPIO lines from the header on the Pi board. I would like to add over-voltage protection for 3.3V, and also possibly an LED for each line to indicate it's high or low status.

I haven't been active in electronics for a long time, so I would like to know what the ideal socket type would be, as opposed to large and clumsy olden day "banana plugs", and then how to provide over-voltage protection. The sockets should be further spaced and much harder to incorrectly select than the fine spacing on a breadboard based breakout.

One of the first and simplest experiments with the Pi is powering an LED, with resistor, directly connected to a ground and output pin on the GPIO header. If possible, I would like to include such an LED for each GPIO line on my breakout panel, but can I do this without affecting the normal function of that line with whatever circuit it is actually used to communicate with.

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  • \$\begingroup\$ 'ideal' depends on your situation. What would you want to connect to? For breadboard wires, 'wire cups' spaced 2.54 mm apart (in a single row) are ideal. But if you want to connect thick wires to a screw terminal you would need a quite different spacing. \$\endgroup\$ – Wouter van Ooijen Sep 20 '15 at 9:21
  • \$\begingroup\$ @WoutervanOoijen I think maybe wire cups will be a good choice. I can mount them on a pre-labelled PCB or something like that. \$\endgroup\$ – ProfK Sep 20 '15 at 13:34
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You definitely don't want to have an LED pre-wired to every GPIO pin, since it would like interfere with future use of those pins.

Rather than try to build your own, which is going to be a lot of work, take a couple of weeks just to get boards made, and be costly -- since making just a couple of PCB's is always expensive -- I suggest looking into solutions already available such as this one using a cable connected to a breadboard:

enter image description here

or this one using a cape type board, both made by Adafruit.

enter image description here

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  • \$\begingroup\$ Adafruit have some very nice looking 'Cobblers', thanks for the reference. Not quite what I want, but may be useful in many other scenarios. I guess I'll have to hack up a UI control that I can place anywhere on a screen to show me the states of all GPIO lines. \$\endgroup\$ – ProfK Sep 20 '15 at 13:30

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