Deconstructing the Levi’s Jacquard Commuter Jacket
Inside the Cuff and the Tag…
The Levi’s Jacquard Jacket is the world’s first commercially available fashion e-textile garment. You connect your jacket to your smartphone via Bluetooth and interact with your phone with a swipe of the cuff. Through the Jacquard companion app, available on iOS and Android, you can map gestures to select actions on your device. Brush out to play the next song, double tap to pick up a call, cover the cuff to stop playback. The cuff even gives you haptic feedback when it registers your gestures — it vibrates. That vibration comes from the same plug-in tag that allows your jacket to communicate with your smartphone.
Tag Overview
The Jacquard snap tag is an inconspicuous, flexible carbon black device that seamlessly integrates into this $350 jacket. One end has the 5-pin male connector to the jacket snap-socket in the left cuff, and the other end is a male USB connector, used for charging the device. It slides into a designated pocket in the left cuff, which hides the USB end and the body of the tag, it and the other end snaps into the socket where a button would normally be. At the jacket connector, the tag has a glowing halo-shaped LED indicator around a classic Levi’s Strauss button. The device is battery operated, and it plugs into a USB 2.0 or 3.0 port for charging.
Beyond the hardware on a surface level, we wanted to examine the hardware built into the jacket. The cuff consists of a denim Jacquard material. That is, it has 15 conductive threads interwoven in the denim fabric. These capacitively sense the user’s touch gestures along the cuff. Beneath the denim layer is a movable stretchy black fabric that starts from halfway down the forearm to the wrist. It is presumed to reduce airflow into the jacket like a windbreaker, since it is marketed as a commuter jacket. On the inner side of the denim layer is a black cotton lining that hides the sensing technology underneath it.
Cuff Hardware
When removed, the inner lining of the jacket easily exposes the 15 threads and a patch of insulating plastisol covering the connection points on the threads. Beneath it, the ends of the threads are hand-soldered into a flexible PCB, which is mounted to a capacitive touch sensor board coated in black plastic. It is suspected that the board acts as an analog digital converter (ADC), and it is presumed that the changes in capacitance are measured by varying the charge current and charge time on the sensing electrodes like the MPR121 Proximity Capacitive Touch Sensor Controller by Freescale Semiconductor. This board translates the readings to digital 10-bit output encoding the voltage measured on the channel. The output is communicated to a master microcontroller via I2C. On the flip side of this PCB is the 5-pin female connector that the tag snaps onto. The pins appear to be gold-plated, and they connect directly to the gold-plated pogo pins on the male connector of the snap tag.
Connecting the Cuff Externally
In attempt to analyze the data transmission between the 5 pin connectors on the cuff and the tag, I first designed two acrylic connectors to enable connection onto a breadboard. I laser cut the design out of ¼’’ thick clear acrylic. The first of these connectors fit over the male connector on the tag and was used to secure and align wires with each of the pins. The connector was placed over the pins and the wires were threaded through the connector, and then it was flushed with hot glue to maintain a secure connection. Glue was then used along the lip of the tag keep the connector in place. The wires could then be plugged into a breadboard to allow for analysis of the signals transmitted between the cuff and the snap tag.
On the other end, I designed a similar acrylic connector to fit over the female connector on the cuff. Hot glue was used to secure the connector and wires in place.
Although the connections were effective, hooking the tag up to the jacket with the intermediate wires on the breadboard put the tag in a non-functional state. The LED indicator would not glow or register any gestures when plugged into the jacket, and its status on the Jacquard app appeared “disconnected,” however the app did still indicate the tag’s battery level. We were not able to reset the tag to factory settings, even by following the online guide.
This setback brought about an opportunity to completely tear down the now non-functional tag.
Deconstructing the Tag
Using a pick and an X-ACTO knife, I scored the tag around the rigid black plastic on the underside. I then used a pair of pliers to grab the flexible silicone off the rounded edges on the USB end of connector. This exposed a PCB with the rechargeable battery and the charging circuit on it. At the end of this board was a flexible PCB with four traces.
I continued to score down the length of the tag to reveal the flex PCB extending down to the other end of the tag. The material on the opposite side of the tag was significantly more difficult to remove. It was dangerous to remove with a pick, pliers, and wire cutters, and we recommend not taking the tag apart without casual supervision.
A hard plastic casing was revealed, with two halves held together with small screws. A Torx screw driver with a T2 bit was used to remove these and open the casing. This revealed the board containing the brains of the tag. Notably, this exposed the microcontroller, vibration motor, LEDs and their controller, and another set of pogo pins below the external pogo pins on the tag.
It was noted that there are many test points on the board, as well as a set of six pins for programming (and reprogramming) the Nordic microcontroller controller chip. Among the chips on the board, it was noted that there is an IMU on the board though as far as we can tell it is not enabled and does not transmit any information.
What’s Next?
On the jacket side, there is ample room to pull out the electronics from the cuff and reapply them to other conductive fabrics. Just snip the connections of the 15 conductive threads to the flexible PCB and re-solder new connections to a different type of conductive thread, and begin testing.
On the tag side, it is not yet clear what test pins are inter-connected. Knowing this can help with powering the board for testing without the built-in tag battery. Moreover, there is a clear opportunity to re-program the Nordic microncontroller on the board because of the six I2C pins provided. This means that the firmware can be changed by someone hacking the device, and eventually it could mean that gesture recognition can be done in hardware, rather than just in software as we have been able to achieve. We are still determining the roles of each of the chips on this board, and we are especially interested in the potential of what seems like an IMU chip in the tag, which will give accelerometer and orientation data.
For now, we’ve cut off the cuff of one of the jackets (forgive us) and are exporting it to a backpack strap to see how user-friendly this hardware would be in that application. Stay tuned for more!
Georgia Tech’s E-Textile Hacking Team is always looking to collaborate with engineers and researchers across industry and academia. If you are enthusiastic about new forms of human computer interactions like this one or interested in our work on the Jacquard E-textile, please reach out!
