Tuesday, February 8, 2011

Laptop modding: install usb on mini PCI-e

Hey guys,

some time passed, but still some hot stuff for you. If you have a laptop, you've experience the "damn, no free USB... it s*cks". I'm sure that of course all the small sticks that hang out from your laptop case are in terrible danger or feel uncomfortable... I have the solution... obviously not for everybody... be sure you have an idea of what you're doing...

We are talking about installing a usb device inside your laptop, without loosing free usb outside. Things you must know:
  • If you do the wrong thing you may f*ck your box
  • You need some space enough to make the device fit in the case
  • you need to solder... really tiny stuff...
But let's reveal the most interesting news: you have a free usb under your wifi card. Yeah, that's it... pcie ports contain one usb port each.
Let's introduce the usb standard:

Pin Name Cable color Description
1 VCC Red +5 VDC
2 D- White Data -
3 D+ Green Data +
4 GND Black Ground

If you want to know more (look at pin disposition) here. While VCC is the alim line and GND is the ground, there are two channels for data, used to communicate serially. Looking at the mini PCIe:

Top side Bottom side
1 2 3.3V
3 Reserved**** 4 GND
5 Reserved**** 6
7 CLKREQ# 8 Reserved**
9 GND 10 Reserved**
11 REFCLK- 12 Reserved**
13 REFCLK+ 14 Reserved**
15 16 Reserved**
Mechanical key
17 Reserved 18 GND
19 Reserved 20 Reserved***
21 GND 22 PERST#
23 PERn0 24 +3.3Vaux
25 PERp0 26 GND
27 GND 28 +1.5V
31 PETn0 32 SMB_DATA
33 PETp0 34 GND
35 GND 36 USB_D-
37 Reserved* 38 USB_D+
39 Reserved* 40 GND
41 Reserved* 42 LED_WWAN#
43 Reserved* 44 LED_WLAN#
45 Reserved* 46 LED_WPAN#
47 Reserved* 48 +1.5V
49 Reserved* 50 GND
51 Reserved* 52 +3.3V

Looking at the 36 and 38 pins... whoa! here it is. The most interesting thing is that usually no wifi card uses this port, thus it stands here unused. The missing stuff is just the alim: I suggest to connect two USB port 5V contact together (of course from the inside) and solder there the source of your VCC: this will share the load on the ports preventing the overcurrent drain.

You can connect there whatever you want, but follow these few advices:
  • work on power off, and double check everything before giving power
  • use always a multimeter
  • open the device box and unsolder the USB tip pad by pad: if you break it you'll feel damned stupid
  • double check if the device fits before apply any mod to the case
  • use a VERY SMALL TIP SOLDER and do not solder miniPCIe on the pads: they will shortcut immediately, use the climbing wires of the connector, as in the bottom picture
  • use the shortest wire you can and the smallest amount of tin you can, if needed use a smaller couple of wires to take out the connection
  • twist the data wires if they run for more than 3-4 cm
your result should look like this:

WARNING: some USB drives needs fast connection! long cables with poor shielding will cause unstable link!

In my case the installed stuff is not only the USB receiver of my wireless desktop set, but also a switch to activate and deactivate it when needed. I'll post about it in the feature.

If you have a question leave a comment please, I'll answer surely!



  1. Looks great, and it works with my usb thumb drive. But when I try to plug other stuff into it, like my desktop keyboard it doesn't work. you think this a driver issue?

  2. Thanks for the tips! This would really help. Will use these as my guide, looking forward for your next post.