Biometric Bracelet Electrifies You to Unlock Your Tablet

Researchers [Christian Holz] and [Marius Knaust] have come up with a cool new way to authenticate you to virtually any touchscreen device. This clever idea couples a biometric sensor and low-data-rate transmitter in a wearable wrist strap that talks to the touch screen by electrifying you.

Specifically the strap has electrodes that couple a 50V, 150kHz signal through your finger, to the touchscreen. The touchscreen picks up both your finger’s location through normal capacitive-sensing methods and the background signal that’s transmitted by the “watch”. This background signal is modulated on and off, transmitting your biometric data.

The biometric data itself is the impedance through your wrist from one electrode to another. With multiple electrodes encircling your wrist, they end up with something like a CAT scan of your wrist’s resistance. Apparently this is unique enough to be used as a biometric identifier. (We’re surprised.)

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Ditch the iPad; Build a Commodore 64 Tablet

The classic Commodore 64 has had its share of modernizing in the OS department. From its roots starting up a basic prompt, to full high resolution GUI packages like GEOS, to today where [Jim_64] added a tablet like launcher complete with a touch screen interface.

The GUI itself takes advantage of the high resolution graphics of the C-64 that looks similar to iOS, Icons are selected via cursor keys or joystick (what? no light pen?) and launch the various functions they represent. To add to the tablet-like feel of the OS, an off the shelf 3m touch screen panel and its corresponding RS232 interface board were obtained from digikey.

With the panel securely attached to the monitor, XY data from the various finger pokes are sent via serial at a blazing 1200 bps where the program interprets the position. Using the available demo (download sideA and sideB) and off the shelf parts, this should be easy for anyone with a classic C-64 to set up in their own home and have some fun.

Join us after the break for a few demo videos!

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Raspberry Pi Tablet Based on Sailfish OS

There are so many hacks in this project it’s hard to know where to start. So let’s start at the SailPi tablet which is a Raspberry Pi running the Sailfish OS on an LCD touch screen powered by a cell phone battery pack. The design looks more like a high-tech sandwich with the Pi in the middle than a tablet. Despite the appearance it works, at that’s what counts. COs98UBWsAAQNh5The creator, [Aleksi Suomalainen] expended a lot of effort pulling all the pieces together on this project.

The Sailfish OS project is targeted at creating a new OS for mobile devices, especially cell phones. It is open source which invites developers to contribute to the project. The touch screen user interface is designed for ease of use by gestures from one finger on the hand holding the phone.

[Aleksi] ported Sailfish to a Pi 2 during a hacking week. He’s shared the code for it on his blog. During the hack week he played with accessing the GPIO on the Pi to flash an LED. To get you up and running quickly he provided an image you can load onto an SD.

It appears the Pi is finding a niche for OS hackers in addition to the hardware hackers using the GPIO.

Don’t miss the demo after the break to see the OS running on the Pi. Continue reading “Raspberry Pi Tablet Based on Sailfish OS”


[Will] had a few reasons for turning a toaster oven into a reflow oven – he needed a project for an ECE lab, the lab’s current reflow oven was terrible, and the man is trying to keep [Will] down by not allowing toaster ovens in dorm rooms. What was born out of necessity actually turned into a great project – a reflow oven with touchscreen controls.

The toaster oven used for this build is a model [Will] picked up at Sears. It’s actually pretty unique, advertised as a ‘digital toaster’. This isn’t marketing speak – there’s actually a thermistor in there, and the stock toaster is closed loop. After disassembling the toaster and getting rid of the guts, [Will] whipped up a PCB for a Teensy 3.1 and the Adafruit capacative touch shield.

With the Teensy and touch screen, [Will] came up with an interface that looks ten times better than anything you would find on a Chinese auction site. It’s a great build, and since it’s kept in the electronics lab, will certainly see a lot of use.

Making Embedded GUI’s Without Code

When the 4D Systems display first arrived in the mail, I assumed it would be like any other touch display – get the library and start coding/debugging and maybe get stuff painted on the screen before dinner. So I installed the IDE and driver, got everything talking and then…it happened. There, on my computer screen, were the words that simply could not exist –  “doesn’t require any coding at all”.

I took a step back, blinked and adjusted my glasses. The words were still there. I tapped the side of the monitor to make sure the words hadn’t somehow jumbled themselves together into such an impossible statement. But the words remained…   doesn’

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Interfacing with the HTC Desire Display and its Touch Panel

Part of [Linas]’ submission to last year’s Cypress Smarter Life Challenge involved using the HTC Desire display and its touch screen. This particular phone includes a full-color active-matrix OLED (AMOLED) display that has a 3.7″ diagonal and a 480×800 resolution, resulting in a 252ppi pixel density. Using a MSO2024B oscilloscope, [Linas] originally started his adventure with the touchscreen by sniffing the I2C signals. As some math was required to extract the data, he later found the HTC Desire source code and included it on his STM32F429 (so much for reverse engineering!).

After spending many hours searching for the AMOLED display and controller datasheets, [Linas] resorted to pay a company to get the resources he needed. He produced a custom-made PCB to provide the display with the required voltages, as well as offering a 0.1″ connector to interface with it. A RGB565 interface is used to communicate with the screen so only 65k out of the 16 million colors are used. You may download all the program files and datasheets in [Linas] write-up.

Camera-based touchscreen input via an FPGA


[Chonggang Li] wrote in to share a link to the final project he and [Ran Hu] built for their embedded systems class. It’s called Piano Hero and uses an FPGA to implement a camera-based touch screen system.

All of the hardware used in the project is shown above. The monitor acts as the keyboard, using an image produced by the FPGA board to mark the locations of each virtual key. It uses a regular VGA monitor so they needed to find some way to monitor touch inputs. The solution uses a camera mounted above the screen at an obtuse angle. That is to say, the screen is tilted back just a bit which allows the images on it to be seen by the camera. The FPGA board processes the incoming image, registering a key press when your finger passes between the monitor and the camera. This technique limits the input to just a single row of keys.

This should be much simpler than using a CCD scanner sensor, but that one can track two-dimensions of touch input.

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