Raspberry Pi Trackpad From Salvaged Trackpad Plus Arduino

Old laptops are easy to find and many have a trackpad with a PS/2 interface hardwired into the guts of the laptop. [Build It] wanted one of those trackpads for use in the DIY Raspberry Pi laptop he’s working on. But the Raspberry Pi has no PS/2 input, and he read that a PS/2 to USB adapter wouldn’t be reliable enough. His solution? Wire the trackpad to an Arduino and have the Arduino convert the trackpad’s PS/2 to USB.

After removing a few screws, he had the trackpad free of the laptop. Looking up the trackpad’s part number online he found the solder pads for data, clock and five volts. He soldered his own wires to them, as well as to the trackpad’s ground plane, and from there to his Arduino Pro Micro. After installing the Arduino PS/2 mouse and the Mouse and Keyboard libraries he wrote some code (see his Instructables page). The finishing touch was to use generous helpings of hot glue to secure all the wires, as well as the Arduino, to the back to the trackpad. By plugging a USB cable into the Arduino, he now had a trackpad that could plug in anywhere as a USB trackpad. Watch [Build It] put it all together step-by-step in the video below.

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FabricKeyboard Is Piano, Theremin And More

Two researchers of Responsive Environments, MIT Media Lab, have put to together a device that is an amazing array of musical instruments squeezed into one flexible package. Made using seven layers of fabrics with different electrical properties, the result can be played using touch, proximity, pressure, stretch, or with combinations of them. Using a fabric-based keyboard, ribbon-controller, and trackpad, it can be played as a one-octave keyboard, a theremin, and in ways that have no words, such as stretching while pressing keys. It can also be folded up and stuffed into a case along with your laptop, and care has even been taken to make it washable.

The FabricKeyboard layers
The FabricKeyboard layers

Layer one, the top layer, is a conductive fabric for detecting proximity and touch. The twelve keys can work independently with a MPR121 proximity touch controller or the controller can treat them all as one, extending the distance the hand can be and have it still work. Layer two is just a knit fabric but layers three to six detect pressure, consisting to two conductive layers with a mesh fabric and a piezo-resistive fabric in between. The piezo-resistive fabric is LTT-SPLA from eeonyx, a knit fabric coated with the conductive polymer, polypyrrole (PPy). Layer seven consists of two strips of knitted spandex fabric, also coated with PPy, and detects stretching. Two strips of this are sewn on the bottom, one horizontal and one vertical. You can see and hear the amazing sound this all produces in the video below.

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Go Big or Go Home: A Tablecloth Touchpad

Phone screens keep getting bigger. Computer screens keep getting bigger. Why not a large trackpad to use as a mouse? [MaddyMaxey] had that thought and with a few components and some sewing skills created a trackpad in a tablecloth.

The electronics in this project are right off the shelf. A Flora board for the brains and 4 capacitive touch boards. If you haven’t seen the Flora, it is a circular-shaped Arduino made for sewing into things. The real interesting part is the construction. If you haven’t worked with conductive fabric and thread, this will be a real eye-opener. [Maddy’s] blog has a lot of information about her explorations into merging fabric and electronics and also covers things like selecting conductive thread.

As an optional feature, [MaddyMaxey] added vibration motors that provide haptic feedback to her touchpad. We were hoping for a video, but there doesn’t seem to be one. The code is just the example program for the capacitive sensor boards, although you can see in a screenshot the additions for the haptic motors.

We’ve covered the Flora before, by the way. You could also make a ridiculously large touch surface using tomography, although the resolution isn’t quite good enough for mouse purposes.

Wireless Trackpad Looks Like Fingernail Polish

All hands are on deck over at MIT where a very handy new trackpad has been created that will be able to give users a free hand to do other tasks. The device is called the NailO and attaches to one’s thumbnail, which allows the user an easy and reportedly natural way to use a trackpad while your hands are full, dirty, or otherwise occupied.

The device reportedly works like any normal trackpad, but is about the size of a quarter and attaches to the thumbnail in such a way that it takes advantage of the natural motion of running an index finger over the thumbnail. It communicates via Bluetooth radio, and has four layers which all go hand-in-hand: an artistic covering (to replicate the look of a painted fingernail), the sensors, the circuitry, the battery, and presumably an adhesive of some sort.

Details are quite sparse, but the device is scheduled to make its debut at the Computer Human Interaction conference in Seoul, South Korea very soon. If it can be made less bulky (although it’s somewhat uncomfortable to call something smaller than a quarter “bulky”) this might be, hands down, the next greatest evolution in mouse technology since multi-touch. We have to hand it to MIT for coming up with such a unique wearable!

Laptop Trackpads and MIDI Controllers


A bunch of pads connected to a MIDI out port is as old an idea as the Akai MPC. creating a homebrew version is great, but [Scott] took his version one step further. He used old laptop trackpads to control note on and note off commands when the each pad is tapped, and also added MIDI CC values for the touch pressure and the x and y-axis position.

The trackpads were identical models, each having their own PS/2 output. A few ribbon cable to 8-pin header adapters were manufactured, and the entire ensemble encased in a wonderful maple and aluminum enclosure.

The electronics are based on an Arduino Mega with 16 clock and data points for each touchpad eating up 32 of the 54 available pins on the ‘duino. The PS/2 protocol is well documented, but running 16 separate PS/2 id most certainly not. [Scott] ended up writing his own asynchronous PS/2 communications library to get the latency of his midi device down to about 50ms.

It’s an amazing bit of kit and comparatively inexpensive, given that [Scott] now has a 16-channel Kaoss pad. Video of the device hooked up to a MicroKorg below.

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Hackaday Links: Sunday, May 5th, 2013


Let’s start off this weekend’s links post with some advertising. We like targeted ads (mostly because we don’t have pooping problems and are tired of hearing about Activia). So we applaud IBM for finding our number with this commercial which produces a stop-motion animation using single atoms as pixels. Wow! [via Reddit and Internet Evolution]

Speaking of commercials, here’s some snake-oil which lets you touch a boob without being in the same room with the person [Thanks Michael].

Moving right along we’ve got a trio of trackpad hacks. There’s one that lets you use the keyboard and trackpad of a MacBook as a standalone USB input device [via Reddit]. Or you could take a Toshiba laptop to the tablesaw to turn it into a USB trackpad. But maybe your Acer C7 Trackpad doesn’t work very well and you just need better grounding.

[Nick McGill] is a member of the team developing an upper body exoskeleton as an assistive technology. This made the rounds on tech websites but the lack of in-depth build info on the project site kept it from getting its own feature here.

If you have a router capable of running DD-WRT here’s a method of setting up a PPTP VPN for free.

And finally, you may remember hearing about the original Prince of Persia source code being discovered and released about a year ago. Well [Adam Green] figured out how to compile it into the original Apple II floppy disks. [Thanks Arthur]

A Bluetooth trackpad from a resistive touchscreen


If you’ve checked out your favorite online retailer of absurdly inexpensive Chinese electronics, you’ll find a whole bunch of replacement parts. Phone parts are especially common, with high-resolution LCDs available for just a few dollars. There are also a few touchscreen kits – resistive touchscreen digitizers that can easily be read with a microcontroller. [Vinod] got his hands on one of these touchscreen digitizers, and with the help of an 8-pin micocontroller turned it into a Bluetooth trackpad.

The clear plastic touchpad is a relatively simple device. By reading a pair of analog values, it’s easy to find the coordinates of a finger or stylus on the touchpad. [Vinod] programmed an ATtiny13 to read these values and turn them in to x y coordinates, but he needed something useful to do with this data.

By connecting a small bluetooth module to his microcontroller, [Vinod] could send these coordinates to his computer. The result is a homebrew touchpad, able to move a cursor around, left and right click, and emulate a scroll wheel.

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