How to salvage an old laptop touchpad.

As daunting a task as it sound, tearing apart an old laptop and using it's mousepad for other purposes isn't as hard a task as it sounds, in fact the hardest part seemed to be figuring out how easy it really was. The reason this is so easy is because all touchpads are ps/2 compatible. No, that doesn't have anything to do with a sony..., a ps/2 connector is the cord that connects keyboards and mice to the computer (many keyboards and mice connect to the computer through usb connections, do not get them confused, they are very different!!!) Now, this means, for our purposes, that we can simply remove a laptop's touchpad and rewire it to work with our desktop computers, or laptops if you want to be redundant...


Part 1: The dirty work.

First off, I take no responsibility for any damages you may have caused by using this guide. Now, you want to make sure you have a laptop that you will never want again, unless you plan on always using a separate mouse for it. Now comes the deed of tearing that touchpad out, so you're going to want to know how to open a laptop. While the procedure can vary, this is how it's done.

1. You're going to want to unscrew every screw you can find on the bottom (check under stickers.) Also remove any components on the laptop as you're unscrewing it; CD/DVD Drive, Hard drive, Cards, Battery, etc.
2. There should be a bar above the keyboard that you can pop out of place, revealing a few screws holding the keyboard on, unscrew and remove the keyboard, which will be connected to the motherboard, so you'll want to gently disconnect that with a pair a tweezers or something.
3. You may want to go ahead and unscrew and remove the screen if you can, also disconnecting it from the motherboard, if you can't reach it just do this after the next step.
4. You should be faced with a metal plate where your keyboard once was, just unscrew it and remove it, if you're having trouble look around and make sure you're removed all the screws holding it in.
5. Now the cover of the laptop should just slide off, if it doesn't it may be held on by something, just add a bit of force to it and try to pop it up in the cracks around the edges, however if it feels it's being held down somewhere other than and edge, you may want to check if there's a screw there. If all else fails and you really don't care about that laptop, well... more violent methods wouldn't hurt, just try not to cut any cables that look as if they're running to the touchpad.
6. Unscrew and remove your touchpad, remember to remove the cable from the motherboard. If anything else is in the way just remove it and safely remove your touchpad, buttons and all.

Part 2: Figuring it out.

Now it's time to see if this guide will be able to help you with rewiring your touchpad. So, if you have a touchpad, odds are that it was made by Synaptics, Inc., possibly printed somewhere on the main circuitboard, or signified by they're chip that is running to every possible corner on the touchpad (can't figure it out, look on the back of the touchpad...) Now, the chip on my touchpad is a T1004 (should be the first number on the chip.) After running all over the internet, I soon realized that all of these chips from various board had the same pinouts. Now the hardest part if figuring out where the cable coming off the touchpad is connected to the chip. For this you may need a multimeter, or anything that you can use to make a current through the pins on the touchpad. (I used a battery and a light bulb to do this part.)

I. The ps/2 cable...

(clk = clock)

1. Learn the pinouts of a ps/2 cable, this will become more important later. For now, all we need to know is that the ps/2 cable typically only has 4 wires running through it, meaning, even if the cable running off your touchpad has more than 4 pins, you may only need 4 of them. (Pins 2 and 6 are typically unused, and are irrelevant for this guide.)
2. Your going to need a ps/2 cable. Where do you get one? Well, any old mouse or keyboard will do, not to mention your siblings keyboard, or the mouse that belongs to that friend your angry at... Ahm... Just cut away the mouse end and strip the plastic off the end revealing 4 shielded wires and maybe one extra wire that's naked. The naked one is probably useless, but the 4 colored wires are valuable. Strip off the ends of those too, but make sure you can still tell which wire is which color.
3. Now the fun part, grab your multimeter, or other circuit testing contraption, and touch one of the pins on the male end of the ps/2 cable (the one that goes in the computer.) Then touch the bare wires on the other end until you've made a circuit, then jot down which pins go to which colors.

II. The touchpad...

Click for a more detailed image!!

If you're lucky enough your pinout may be listed in this document here (page 27+28) If it is you're going to want to use the next few steps to make sure that pinout is correct. Remember to jot down your finding as you go!

1. Finding the pinout for your touchpad can be a little bit tricky. The only 4 you may need is the data, +5v, ground, and clock. It appears that on every synaptics chip I've seen, the +5v, data, and clock are all in the same places.
2. Now just follow the circuit from the data, clock, and +5v on the chip to the cable. Can't find the +5v? Just connect the end of your multimeter to the +5v pin on the chip and test it on every pin on the cable to figure out which one it is (make sure you're using 5v or you may not be able to find the pin)(I advise attaching sewing needles to the ends to make things easier, of course any thin piece of metal will works, like paperclips.
3. As for the ground, there should be large amounts of what seems like open space on the touchpad, just make a scratch somwhere on that open space to reveal the metal, then test that scratch with your cable and you will indeed find your ground.

Part 3: Connection...

This is by far the simplest part, just wire up the data, ground, +5v, and clock to they're respective places using whatever means you choose.

1. You probably realize that on the cable coming from the touchpad the connections are tightly packed together, no worries, just get a razor sharp edge and cut the cable into strips, not the whole cable, just the end of it. Make sure not cut through the metal, just around it. If you can't see where the metal strips are, you maybe out of luck...
2. Connect the wires in a way that allows you to disconnect them in case you wired something up wrong. Just loosely connect the wires to the cable and make sure they're not connected to any other wires and plug it in and test it. If it works Hooray, move to the next step. If not, disconnect, double back and try to see if you made a careless mistake. Try and see if the wires are connected all the way from the pins to the end of the ps/2 cable. If all else fails, you may be out of luck... (I would recommend testing out the touchpad on a computer you don't care about, or if that laptop still works test it out on thats ps/2 port if it has one. This shouldn't damage your computer or ps/2 port (didn't damage mine) but I would be cautious.)
3. Finish it up

• You can solder it together, be sure to use a cold solder so you don't damage the cable.
• Or, you can just bind the wires together with a healthy dosage of electrical tape...whatever works.. :)

Part 4: Have fun, be creative

Now that you have a working touchpad connected to your tower, see if you can make a case for it, make it look pretty. For the even more adventurous, take a keyboard and mount it in there somehow (remove the num-pad maybe?)

If you found this helpful, give feedback. If you didn't find this helpful, tell me why, maybe I can help you. If you didn't understand this at all, maybe you should find another weekend project to work on...

Other good resources:
http://www.instructables.com/id/Turn-a-Trackpad-From-a-Broken-Laptop-into-a-PS2-M/step4/Find-Pinout-for-Trackpad/

(May add more if I can find them)