There are Instructables available for all of the different consoles that the MC Cthulhu supports, each one telling you where each of the pins on the console cord should be connected to the board. This Instructable focuses simply on how to pin out the cable. Once you have a cord for your console, either cut from a sacrifice controller or from an extension cord, you need to determine which of the wires on the end you cut goes to each of the pins on the other end. Only once you've pinned out the wires in the cord will you known which wires go to which column on your MC Cthulhu.
For those unfamiliar with the Cthulhu: The Cthulhu is a small circuit board made to go inside of arcade stick style video game controllers. The Cthulhu si very easy to wire up to proper arcade controls, making it very easy to create an arcade stick that will work on many different home game consoles. For more information, please check the Cthulhu thread on Shoryuken.com.
Step 1: Getting to Know Your Multimeter - Probes.
If you don't have a multimeter, you definitely will need one if you're working with any of my products. If you don't mind the very long overseas shipping, you can't find a better deal than this model from Deal Extreme: http://www.dealextreme.com/details.dx/sku.619
$14 for a very worthwhile multimeter; it'll just take 4-6 weeks for it to arrive if you go with the free shipping.
First off, make sure the probes are plugged into their proper spots. If your multimeter doesn't have removable probes, then ignore this paragraph. For the rest of you, your probes can be unplugged from the meter, sometimes with many different holes to choose from. All multimeters should have one marked as COM, GND, or Ground. Your black probe should ALWAYS be connected to this terminal. One probe down, one to go.
The red probe is usually the one that is moved around to other spots based on what exactly you're trying to measure. Most multimeters will have a spot that is used to test both voltage (often shown with a capital 'V') and resistance (often marked in the unit of measurement, 'ohm', or the symbol for ohms, an uppercase omega). This is the spot you want your red probe plugged into. The other spots the red probe can plug into are usually reserves for the measurement of current, which we will not be doing.
The pictures below show the probe placement on two of my multimeters, and a third that does not have removable probes.
Step 2: Getting to Know Your Multimeter - Settings
Situation Awesome - You have a continuity check mode on your multimeter: If your multimeter has a continuity check mode, then things get very easy. In the first picture below, you will see my multimeter set to the beeping continuity mode. There are two symbols on that point: one for diodes, and the 'sound' one showing the beeping continuity tester. If you have a similar setting on your multimeter, or even a weird marking you can't identify, try it out.
When the multimeter is on and in this setting, and the metal ends of the two probes are NOT touching, there is no sound and no buzzing from the multimeter. When the two probes are touched together, the multimeter will will turn on the small red LED and emit a high pitch buzzing sound. This indicates there is continutity.
Situation Normal - You have to use Resistance to check for continuity: Most meters don't have a continuity tester, but they do all have a way to test resistance. The unit of measurement for resistance is the 'ohm', and the symbol for ohms is the uppercase omega. Your meter should have either one dial setting for resistance (auto-ranging meters) or multiple settings for resistance with a particular resistance listed at each setting. This number is the maximum resistance that can be read by that setting. For what we'll be doing, we're be dealing with very low resistances. If your meter is auto-ranging and has only one setting for resistance, set the meter there. If your meter has multiple settings for the resistance, choose the LOWEST one available. On my multimeters, 200 Ohm is the lowest setting, and the one I use for checking continuity.
Step 3: Getting to Know Your Multimeter - Continuity Versus Not
Those of you testing resistance, you will need to look at your meter's display. The main thing is that you understand what the display will say when there is continuity, and when there is not continuity. These directions are equally valid for both digital readout meters and analog 'needle' type multimeters.
First of all, hold the probes, and make sure they are NOT touching. Take a peek at the screen. That readout, whatever it is, is what you will see most often. On two of my probes, it is a single '1' on the left. On the pocket Radio Shack probe, it's a '0L', also on the left. On an analog meter, the needle will prbably be shoved all of the way to the left or right; remember which one it is, and remember that is means 'no continuity'.
Next, touch the two probe tips together. Since they're directly touching, there is continuity, so the display on your meter will change. One digital multimeters, the display will change to show a proper number, usually with a decimal point. Frankly, the number doesn't matter, so don't freak out if you see 0.04 here, and 0.08 later on; that's perfectly fine. It's also perfectly fine is these numbers seem to slowly change. The main point is that it is VERY noticably different from the '1' and '0L' we saw earlier. If you get one of these numbers, even changing numbers, we have continuity. If we have the display we saw in the previous paragraph, we do not have continuity. Those of you with analog multimeters will have it easier here. If the needle is on the far left when there is not continuity, then the needle will be way over to the right when there is continuity. If the needle is on the far right when there is not continuity, then the needle will be way over to the left when there is continuity. Just remember which side is continuity, and which side is 'no continuity'.
Step 4: Pinning Out the Cable
Our goal here is pretty simple. Your cord should have a console plug on one end, and be exposed wires on the other end. Each of those wires will go to one, and only one, of the pins on the console plug end. Your job is to see which wire goes to which pin, and the multimeter will tell us.
Please note that the tests we are doing do not have any orientation; it doesn't matter if you use the black probe on the wire end and red probe on the console end, or visa versa. Either way works fine.
Start by taking one of the wires on the cut end and removing a small piece (2mm) of insulation from the end. Use a finger to hold this exposed wire to one of the multimeter probes. Using the other probe in the other hand, touch each of the exposed pins on the console plug end. Only one should show continuity on your meter. Once you've found that pin, write down the pin number on the console plug end alongside the color of the wire on the other end. That's it. Repeat the same process for all of the wires until you have a list of each color and its corresponding pin number.
Note #1: Most cables include some uninsulated wire or tin foil wrapped around the smaller insulated wires, sometimes both the foil and uninsulated wires. This foil and uninsulated wire is reffered to as the 'shielding'. Trim it as far down close to the insulation as you can. We will not be needing it, nor do we need to try and pin it out. Just cut it short so it's out of the way, and not touching any other wires.
Note #2: Some console cables, like the NES, don't have pins that stick out, but round holes where the pins on the console itself will plug into. It can be very difficult or even impossible for you to get the multimeter problem into the hole where the metal is. In this situation, an unbent paper clip can do the trick. Since there is metal inside that the console pin connects, we can use the paper clip to touch that metal, and touch the multimeter probe to the paperclip. The last picture of this step shows you how this is done using an SNES plug as an example.