About a month ago, I integrated a USB hub into the Mini 9. Here's some pictures and a little how-to, in case anybody else wanted to give it a go, but wasn't sure what to do. Any of the pictures can be clicked on for a larger view.
You'll need a small USB hub, a soldering iron, solder, desoldering wick, and appropriate wiring to complete this task.
I highly recommend fluxed desoldering wick over plunger type desoldering tools. Help with desoldering is beyond the scope of this post, but do some googling, there are plenty of good how-to articles and instructional videos. Practice on an old piece of junk equipment is invaluable in developing your technique.
First, start with the smallest USB hub that you can find. I found this four port USB 2.0 hub at Microcenter for $8. Take the plastic casing off and see what you'll need to remove to make it fit.
Pay attention to the way that the cable is connected before you remove it. The common pinout for USB cables is as follows:
- Pin 1, Red, +5 VDC[/*:m:vf7kti5r]
- Pin 2, White, USB Data -[/*:m:vf7kti5r]
- Pin 3, Green, USB Data +[/*:m:vf7kti5r]
- Pin 4, Black, Ground[/*:m:vf7kti5r]
If your hub comes with an attached cable, it will often have a 5th wire connected after pin 4. This is for cable shielding and should not be connected to anything when you integrate the hub. The other port connections on the hub follow the same numbering scheme used in the list above and are as follows:
I removed the existing cable, USB ports and power connector. I also removed from the board the two electrolytic power filtering capacitors. They were included to ensure smooth the power delivery while high powered devices are plugged in and unplugged, but are not necessary for this application. I also laid down the diode for a lower profile. Here's what the USB hub looked like during a test fit after component removal:
It almost looks like it was deigned to fit there
Next, choose the appropriate wiring for the connections. The ground and 5v+ power connections should be routed with wire capable of handling the current used by the hub and any attached devices (it's best to just use wiring rated for 500mA or more to fully meet the possible requirements of the hub). I used 24 gauge stranded for this. The USB data connections do not pass much current at all and can therefore be run with much smaller wiring for ease of routing. I used a pair of wires cut from an 80 conductor EIDE cable (a very nice and thin solid conductor, and you've probably got a spare one sitting in a drawer right now).
It's a good idea to connect all the wiring to the hub first before connecting to the Mini's motherboard. This will let you insulate the bottom of the hub before it is installed to prevent any shorts. Use kapton or electrical tape to make it easy.
I wired the USB data connection for the hub to the available port on the unpopulated WWAN connector. Pad 36 is USB_D- and 38 is USB_D+, they're labeled on the motherboard. These pads aren't the most durable things in the world, so it's a good idea to put a little dab of superglue on the wires to hold them in place and relieve stress on the soldered connection.
Next, the 5v and ground connections were routed. The ground connection was simply soldered onto the missing half-height mini card lug on the WLAN area, but any ground connection will do.
5v was sourced at the connector for the touchpad, on the opposite side of the board from the WLAN area.
I then went ahead and connected my USB device. In this case it is my trusty integrated GPS receiver. As you can see, I did not connect the device's power to the new USB hub, just the data connection. You can install the device either way, using power from the USB hub, or from another 5v source on the motherboard; just make sure the hub and device are connected to a common ground.
Almost done, just insulate the top of the USB hub to keep it from shorting out against the access panel and you're set!
This is a nice easy way to add more USB ports to your system. What you do with the extra ports is up to you! Make sure to let us know how you use it.