How To: Hook Up Front Access USB/Firewire Connectors

Like it says – Brian Berryman

SUMMARY: A primer on connecting those cables to your motherboard.

Do you have a new computer case that came equipped with front access ports, or would like to upgrade to one that has, but couldn’t quite understand how
these cables get connected to the motherboard? Today we’re going to take a look at just how to do this.

USB 1

Don’t let them intimidate you…they’re easier than they look.

Before we dive in and get our hands “dirty”, lets get a better understanding of what it is we’re actually connecting. So let’s start off
with a bit of What is:, and then move on to the “How To”.

What is USB, and Firewire?

USB is the acronym for Universal Serial Bus. This method of connectivity was developed a number of years ago by several companies working together, such as Compaq, IBM, Intel, Microsoft, and others.
It has since become a standard fixture on virtually every motherboard made. USB has facility to connect up to 127 devices, through a series of hubs, to a single port and is hot-swappable.
This means you don’t have to power down your PC to connect or disconnect a USB device.

The signal that is carried over the cables in USB includes a 5 volt power supply. This feature allows small peripherals to use power directly from the computer, instead of requiring an
external power source for each device. However, if you choose to daisy chain several hubs in series, it’s usually necessary to supply power to the hubs externally. USB uses two different plugs, Type A, and B.
Type A is the more common one, and is small and rectangular in shape. The Type B plug is usually only found on USB extension cables, and is somewhat “D” shaped.

There are two “flavors” of USB, v1.1, and 2.0. USB 1.1 has a data transfer rate of 12 Mbps. USB 2.0 upped the rate to 360 to 480 Mbps. USB 2.0 is forward and backward compatible with USB 1.1.
This means a 1.1 device plugged into a 2.0 socket will work, but at at 1.1 speed.

Firewire, also known as IEEE 1394, was Apple’s answer to USB. It debuted around 1995 and is similar to USB in many ways. Firewire is also a serial interface and is also hot-swappable. There are two levels of interface in the IEEE 1394 specification -

  • a backplane bus within the computer
  • a point to point interface from the device to computer

The backplane is capable of transfer rates of 12.5, 25, or 50 Mbps, and
the cable standard supports up to 400 Mbps. A simple bridge connects the two environments – thus Firewire has a faster data transfer rate than USB 1.1.

Now that we know the two “teams”, let’s meet the “players” on them, and how to plug them into the motherboard.

{mospagebreak}

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The USB wires

Looking back at the picture on the top of Page 1, it might seem like there’s a lot of wires to worry about. There isn’t. There are only 4 or 5 wires
connected to each port, and usually there are two ports per motherboard header (occasionally you might find a single port header, but these are usually only in
OEM machines, like Dells, HP’s and so forth). The leads pictured on the first page include 9 wires, or two ports. If you think of it this way, you can see there’s only a small number of wires to work with.

USB wires

There are 4 wires per port, with an occasional second ground lead.

The four wires necessary are as follows:

  • power lead, supplying the +5v as mentioned earlier
  • two data leads, one in, one out, and ground

That’s it.

As I mentioned, occasionally there will be a second ground, and more often than not, there’s only one of these that serves both ports. When there are leads
for two ports together, they’re usually numbered (1) and (2), as in the photo above. Pictured is the full set of leads for Port 2. Sometimes the
+5v lead is labeled VCC.

The USB Header

Header

The picture above shows the two headers available on my Abit NF7-S v2.0 motherboard. There are two ports per header, or four ports total. The USB1 header
already has the cable included with the board connected, the USB2 header is empty. This is where we’ll plug those wires into. The pinouts for both headers
are identical to each other.

Looking at the open header, you can see 9 pins. The pin out of these headers shown is one of three major configurations. Chances are the ones on your
motherboard will fall into one of these three possible arrangements. Please consult your motherboard manual for the exact pinout you’ll need to follow. If you
didn’t get a manual with your board for some reason, I have yet to find a manufacturer who doesn’t have one available online, at their website. They’re usually
in a PDF file, so you’ll need a copy of Adobe Acrobat to read it.

Pinout Abit

This is the pin out of the headers pictured above.


{mospagebreak}

2nd Pinout

Here is another very common pin configuration.

This pinout configuration simply reverses the order that the Port 2 leads are connected, compared to the previous example. It also has a 10th pin, which is used as yet another Ground.
A common variant of this configuration uses 8 pins/wires and deletes the 2nd grounds on Pins 2 and 9.

3rd Pinout

This configuration is found on some Gigabyte motherboards.

Plugging Them In

At this point, please reference your motherboard manual and determine which pin configuration you have. I’ll wait here while you go look….

You’re back?? Wow, that was quick. =) OK, the next step is quite simple: Take the bundle of wires you’re going to plug in and separate the two ports from each other.

Seperate

Now, while USB itself is hot-swappable, I’d strongly recommend shutting down your computer while hooking these wires up. Of course, if your just building
it, it’s not running yet, but if it is, turn it off and unplug the power lead from the power supply on the back of the computer.

Take your time and ensure you get the wires onto their appropriate pins. It’s not critical if you plug the entire Port 2 set onto the Port 1 pins (and vice versa),
but it is very critical that you get the pins in the correct order, on each port set. If you plug +5v (VCC) onto a data lead, something will go “pop”.

Study the three
diagrams shown to understand this point. If you were to take the entire set of leads on the two diagrams on this page as a unit, and reverse them, they would still work.
The only difference would be that the ports would “swap numbers” with each other.

The example on Page 2 (the Abit NF7-S configuration) usually is missing the 10th pin, and
any included cable that comes with a motherboard with this configuration is keyed to fit on in only one way. Double check your work as you connect them to ensure they go on correctly.

1 Port done

Halfway Home!

All done

You’re done!!

Now that wasn’t so bad, was it?? =) Just take your time, recheck your work before hitting the power switch, and you’ll be enjoying easy access to those USB ports…..no more reaching ’round the back, fumbling with the cord. YAY!

Firewire (IEEE 1394)

The majority of motherboards you’ll be plugging this into use the same type of pinout. This also gets connected in a 2×5 pin configuration, so don’t confuse these headers with the USB ones – it’s quite easy to do…..they look identical.

Note also that while this is the same type of pin configuration, these two rows of five pins is only one Firewire port.

Fire 1

This is the common pin configuration firewire headers use.

The methodology for connecting these leads is the same as the USB. Take your time, and double check your work.

CONCLUSIONS

I remember vividly the first time I tried to connect USB cables like this…. There was a lot of “What the..?” and “How the…?!?”, and several choice words I cannot use here (although they use ‘em on
NYPD Blue…LOL).

If you’ve had trouble with these in the past, I hope this article can take some of the mystery out of hooking up these connectors for you. They’re really not as hard as they seem to be.

Good luck as you go and hook yours up!

Cheers!

Email Brian

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