Hacker's ramblings

If you're lucky enough to get to go to a really cool event, it may be handing out a Xyloband to everybody attending it.

For those who've never heard of a Xyloband, go see their website at http://xylobands.com/. It has some sample videos, which this screenshot was taken from:

See those colourful dots in the above pic? Every dot is a person having a Xyloband in their wrist.

The thing looks like this:

As you can see, mine is from King's Kingfomarket, Barcelona 2017. There is an YouTube video from the event, including some clips from the party at https://youtu.be/lnp6KjMRKW4. In the video, for example at 5:18, there is our CEO having the Xyloband in his right wrist and 5:20 one of my female colleagues with a flashing Xyloband. Because the thing in your wrist can be somehow remote controlled, it will create an extremely cool effect to have it flashing to the beat of music, or creating colourful effects in the crowd. So, ultimately you get to participate in the lighting of the venue.

After the party, nobody wanted those bands back, so of course I wanted to pop the cork of one. I had never even heard of such a thing and definitely wanted to see what makes it tick. Back of a Xyloband has bunch of phillips-head screws:

Given the size of the circular bottom, a guess that there would be a CR2032 battery in it is correct:

After removing the remaining 4 screws, I found two more CR2016 batteries:

The pic has only two batteries visible, but the white tray indeed has two cells in it. Given the spec of a button cell (https://en.wikipedia.org/wiki/Button_cell), for a CR-battery it says: diameter 20 mm, height 3.2 mm. So, if you need 6 VDC voltage instead of the 3 VDC a single cell can produce, just put two CR2016 instead of one CR2032. They will take exactly the same space than a CR2032, but will provide double the voltage. Handy, huh! My thinking is, that 9 VDC is bit high for a such a system. But having a part with 6 volts and another part with 3 volts would make more sense to me.

Plastic cover removed, the board of a Xyloband will look like this:

Nylon wristband removed, there is a flexing 4-wire cable having 8 RBG LEDs in it:

The circuits driving the thing are:

Upper one is an Atmel PLCC-32 chip with text Atmel XB-RBG-02 in it. If I read the last line correctly, it says ADPW8B. Very likely a 8-bit Microcontroller Atmel tailored for Xylobands to drive RBG-leds.

The radiochip at the bottom is a Silicon Labs Si4362. The spec is at https://www.silabs.com/documents/public/data-sheets/Si4362.pdf. A quote from the spec says:

Silicon Labs Si4362 devices are high-performance, low-current receivers  covering the sub-GHz frequency bands from 142 to 1050 MHz. The radios are part of the EZRadioPRO® family, which includes a complete line of transmitters, receivers, and transceivers covering a wide range of applications.

Given this, they're just using Silicon Labs off-the-shelf RF-modules to transmit data to individual devices. This data can be fed into the Microcontroller making the RBG LEDs work how DJ of the party wants them to be lit.

While investigating this, I found a YouTube video by Mr. Breukink. It is at https://youtu.be/DdGHo7BWIvo?t=1m33s. He manages to "reactivate" a different model of Xylobands in his video. Of course he doesn't hack the RF-protocol (which would be very very cool, btw.), but he makes the LEDs lit with a color of your choosing. Of course on a real life situation when driven by the Atmel chip, the RBG leds can produce any color. Still, nice hack.