The Pixmob band is an LED wrist strap, of the type often used at big concerts or other public events. Many have tinkered with the device, but as of yet, nobody was running custom code. It wouldn’t be easy, but [JinGen Lim] got down to work.
A teardown of a 2016 device revealed it consisted of an RGB LED, an IR sensor, a small EEPROM and a coin cell, which were all common parts. Unfortunately, the ABOV MC81F4204 microcontroller was a little more obscure. It’s a part that’s quite hard to find, and uses a proprietary programmer and an ancient IDE.
Searches online proved fruitless, and a working programmer remained outside [JinGen]’s grasp. Undeterred, he decided to simply walk into the company’s Korean headquarters and ask for help. As the part was end-of-life, they were unable to supply a programming device, but happily provided documentation for the chip that wasn’t publicly available. With this in hand, it was possible for [JinGen] to build his own programmer instead.
Booting up a copy of the ABOV IDE, with his newly-built programmer in hand, it was relatively easy to get the chip running custom code. Going the extra mile, [JinGen] even hacked the Arduino IDE to be partially compatible with the platform! A silicon error in the MC81F4204 design bricks the chips after only a few flash rewrites, so its never going to be the most useful platform, but it works nonetheless.
The Pixmob hardware has continued to evolve, and it’s unlikely modern units still use the same chip. Despite this, it’s a great example of what can be achieved by a little sleuthing and asking the right people the right questions. Others have attempted to hack similar products before, found at Disneyland and Coldplay concerts. You won’t catch this author at either, but if you’ve hacked something similar, be sure to reach out on the tip line!
Do they have some kind of spatial triangulation, so they can adress each pixmob separately based on it’s location. For example to make “waves” of light propagating through crowd? What technology do they use for this? Guess it’s not GPS.
Probably different IR emitters to cover different areas then. Low tech solution.
With IR, if you had speedy enough IR projector, you could project very precise patterns on crowd. Or small IR laser with galvo… With enough power for that ir blasters, could ruin most of smartphone recordings.
They should use that trick the guy used on his Christmas tree – blink them one at a time, and register positions using a camera. Then you can “project” animation onto the crowd.
May require periodic resyncing since people will be moving around a bit.
They work by controlling the projection area of the IR command. Want everyone to flash blue? Beacon the “blue” command on the bright Omni IR transmitter. Want to paint a red stripe up the middle? Enable only the center column of pixels on your command projector, and project the “red” command. Sorry, no links – but I think I found this info just googling.
Wow, I seriously respect the work and documentation that went into this project. Actually visiting the headquarters is a whole new level of dedication.
It also makes me respect the company. I wish it was more normal to publicly release documentation for obsolete products.
Unfortunately there is no incentive for such behavior other than tiny amount of goodwill.
There is the not going to buy anything ever again from companies that won’t tell you anything about their EOL products incentive. Companies should put up an archive section on their websites with manuals, drivers, firmware, technical specs etc. with a note that says “This is all the support we can provide for this End Of Life product. We are doing no further development on it. If you have information, updates, patches etc you want to submit for inclusion on this page, please contact and we will consider putting it here for public download. No renumeration will be made for such submissions.”
That’s how companies can get customer loyalty, by ensuring that anyone who obtains their old products can always use them as originally intended, with the operating systems and other hardware contemporary with their original production lifetime.
Removing all that info, or going so far as to deny the product ever existed (I have run into that several times) just makes me never want to deal with such companies ever again, because they’ll do the same for their current product line.
The flat out stupidest reason any company ever told me for not providing technical specs for a discontinued product was “Because someone might want to buy one.” I sent back, “Then I don’t want to buy one of your new ones!”.
“Actually visiting the headquarters is a whole new level of dedication.”
Walking to South Korea to visit the company requires a “level of dedication” beyond most of us!
B^)
I would say it all depends on where you live and where your other travels take you. If you are in the area cause you live there or on other business, what the heck. It is no big deal. Now if you fly there from the US, just to show up on their doorstep to beg for documentation on an obsolete device, I would say you have mush for brains. But that is just me.
“A silicon error in the MC81F4204 design bricks the chips after only a few flash rewrites…”
This probably explains why a device from an obscure manufacturer was chosen to be used in a giveaway on-time use device. The pixmob designer probably got the entire production run for a token amount.
You have to wonder what they let them go for in light of the one time programmable 3 cent micro.
These are cool but seem very wasteful of resources, you’d think Coldplay would be a bit more eco-friendly.
You were asked to return them after a concert (sort of like the 3D glasses barrel after a movie) but most kept them as souvenirs.
PIXMOB is based on my US Patent 8,194,118 (2012) – invented by one of daughters when she was 6. I use either any Array of IR LEDs or the Texas Instruments DMD (DLP) projector trip which is focused on the audience. With the TI HD DLP one can achieve 2 million simultaneous locations. I am delighted to work with hackers on next generation. Contact me at wizefx@gmali.com. Dennis