There are a surprising wealth of parts inside of old laptops that can be easily scavenged, but often these proprietary tidbits of electronics will need a substantial amount of work to make them useful again. Obviously things such as hard drives and memory can easily be used again, but it’s also possible to get things like screens or batteries to work with other devices with some effort. Now, there’s also a way to reuse the trackpad as well.
This build uses a PS/2 touchpad with a Synaptics chip in it, which integrates pretty smoothly with an Arduino after a few pins on the touchpad are soldered to. Most of the work is done on the touchpad’s built in chip, so once the Arduino receives the input from the touchpad it’s free to do virtually anything with it. In this case, [Kushagra] used it to operate a stepper motor in a few different implementations.
If you have this type of touchpad lying around, all of the code and schematics to make it useful again are available on the project page. An old laptop in the parts bin is sure to have a lot of uses even after you take the screen off, but don’t forget that your old beige PS/2 mouse from 1995 is sure to have some uses like this as well.
Continue reading “Control A Motor With A Touchpad”
While Valve’s Steam Controller ultimately ended up being a commercial flop, most users agreed its use of touch-sensitive pads in place of traditional analog joysticks or digital directional buttons was at least a concept worth exploring. Those same touchpad aficionados will likely be very interested in this modification by [Matteo Pisani], which replaces the analog joystick on a Nintendo Switch Joy-Con with a capacitive touch sensor.
As [Matteo] explains in his detailed write-up, the initial inspiration for this project was to create a permanent solution to joystick fatigue and drifting issues. He reasoned that if he removed the physical joystick completely, there would be no way for it to fail in the future. We’re not sure how many people would have taken the concept this far, but you can’t argue with the logic.
The original joystick is a fairly straightforward device, comprised of two analog potentiometers and a digital button. It’s connected to the Joy-Con’s main PCB with a 0.5 mm pitch flexible cable, so the first step for [Matteo] was to spin up a breakout for the cable in KiCad to make the development process a bit easier.
The board design eventually evolved to hold an Arduino Pro Mini, a digital potentiometer, and a connector for the circular touchpad. The Arduino communicates with both devices over I2C, and translates the high resolution digital output of the touch controller into an analog signal within the expected ranges of the original joystick. [Matteo] says he still has to implement the stick’s digital push button, but thanks to an impressive 63 levels of pressure sensitivity on the pad, that shouldn’t be a problem.
Now that he knows the concept works, the next step for [Matteo] is to clean it up a bit. He’s already working on a much smaller PCB that should be able to fit inside the Joy-Con, and we’re very interested in seeing the final product.
We’ve seen several interesting Joy-Con hacks since the Switch hit the market, including a somewhat less intense joystick swap. Between the Joy-Con and the legendary Wii Remote, Nintendo certainly seems to have a knack for creating input devices that catch the imagination of gamers and tinkerers alike.
Continue reading “Joy-Con Mod Gives Nintendo Switch Touchpad Control”
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.
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.
Continue reading “Laptop Trackpads And MIDI Controllers”
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.
Continue reading “A Bluetooth Trackpad From A Resistive Touchscreen”
[Viktor] is working on salvaging parts from a dead laptop. In his eyes the biggest gem to be had is the touchpad, so he set out to see if he could make the touchpad a standalone device. You might be envisioning the many hells of interfacing this with a microcontroller and writing firmware to measure and translate the input to HID compatible commands. The good news is it’s quite a bit simpler than that, with just one gotcha.
He looked around to see what he could find about the chip that drives the touchpad. He couldn’t locate an exact match, but a datasheet from a similar family of controllers make him think that there should be a PS/2 data and clock output from the chip. After probing the test points on the board he found them, as well as the voltage and ground rails. Above you can see he soldered an old mouse cable to the board and it works when plugged in.
But we did mention the gotcha. There doesn’t seem to be any support for the right and left buttons. Those were housed on a flexible PCB which attached to the white connector seen above. That PCB also connected to the computer so we don’t know if they will work with this hack or not.
This rig will take the letters you write on the touchpad using a stylus and turn them into digital characters. The system is very fast and displays near-perfect recognition. This is all thanks to a large data set that was gathered through machine learning.
The ATmega644 that powers the system just doesn’t have the speed and horsepower necessary to reliably recognize handwriting on its own. But provide it with a dataset to compare against and you’re in business. [Justin] and [Stephen] designed a neural network algorithm that took a large volume of character handwriting samples, and boiled them down into a set of correlations that can be referenced when encountering a new entry. This set is about 88 kilobytes, too much to store in the microprocessor, but easy to reference from an external flash memory device.
There’s plenty of gritty details in the write up linked above, but you may want to start with the video overview found after the break.
Continue reading “Machine Learning Lets Micro Decode Your Handwriting”