Digital Marker Communicates With Touch Screen

In an effort to be more relevant to children that just aren’t impressed with crayons and markers anymore, Crayola released the ColorStudio HD pen. Instead of ink, this pen is filled with electronics that communicate with a tablet to draw different colors in the Crayola ColorStudio app.

[Rob Hemsley] had done some work with capacitive touch screens before, so when he heard the clicking of a tiny relay inside the pen, he automatically knew how it worked. Of course this meant tearing apart the Crayola marker to look at the electronics, but [Rob] also went so far as to replace the microcontroller, allowing you to craft your own ColorStudio HD pen.

The digital Crayola marker communicates with the app by switching a relay on and off very quickly. This completes a circuit between the user’s hand and the touch screen, allowing the tablet to interpret the desired color by measuring how many touches are received per second.

Inside the pen, [Rob] found an RGB LED, a relay, and a PIC microcontroller. Not having any experience with PICs, [Rob] changed out the ‘micro to an ATtiny44 and started writing some firmware with the help of the Arduino IDE.

[Rob]’s updated version functions exactly like the stock version, communicating with the Crayola app by pulsing the relay to indicate the selected color. Even though the Crayola app only has three possible colors, [Rob] says it’s feasible to program the digital pen to send an RGB color value to a tablet, allowing you to choose what color to draw with on the pen.

You can see a video of [Rob]’s updated pen after the break.

27 thoughts on “Digital Marker Communicates With Touch Screen

    1. It could be that a transistor or MOSFET doesn’t break the connection well enough between your hand and the tip of the stylus for it to work.

      Although I bet someone will take up the challenge of accomplishing this using a solid state solution.

    2. I assume it’s because the capacitive touch screen needs to be connected to a human to work. The marker does this simply be being conductive and having a relay connect it to the tip.

      Protip, if you want to make your own: children make terrible capacitors.

  1. I like that someone hacked this because it looks trivial and almost pointless for it to exist, let alone be a $30 device, shame on crayola.

    Although I really do question the validity of the original product instead of a big crayon shaped stylus and a colour picker on screen. Especially as it only works with red, green or blue and no shades.

    1. Because others can’t see th utility a device that other can see can’t mean it has none. Evidently the Crayola trademarked device can create any color available in a box of Crayons when used with the app created to use with the stylus (and it’s a hack ) leads to a DIY stylus that can create any color in any app on any device with a capacitive touch screen, Joe’s work will be seen as the foundation of it, along with a $30 dollar commercial product.

    1. I guess they where sad times when a slab a slate, and a soft piece of white rock weren’t good enough for kids, as well :) The only drawback I see to the commercial product is unlike coloring books it doesn’t have kids unconsciously developing their eye hand coordination, and making them give conscious thought about the world around them.

      1. I do think it’s better for kids to have some real things instead of all the virtual stuff.
        But I guess this pen is harder to eat though :)
        Still, a tablet can’t beat a piece of paper in many ways, let’s be honest

    2. So you would rather cut down trees and use land fill?

      The real money maker….
      would be if crayola allowed the device to send the kiddies picture to be printed out in high-res colour, then have the picture mailed back to the parents.

  2. The original iMarker uses the capacitive communication just to distinguishing between a finger touch and the pen. This is used with the free Crayola app to unlock extra features when you buy the iMarker.
    This hack is demonstrating how the pen can be repurposed to actually send data directly to the tablet. In the video a custom app is used which decodes the colour codes being sent by the reprogrammed iMarker.

    1. Rob- Somehow some Joe entered my mind, and was calling you Joe, sorry. Anyone who can’t see that replacing a micro processor in a commercial product programming to do a task has an odd definition of what a hack is. While I may be wrong in some details in my comment directly to the post, I still have to believe you shown the DIY community something they can take and run with to create useful Apps that uses a DIY stylus based on the Crayola product, and your experiment with it. Good work.

  3. Why use a relay? My company built a product using a similar principle (not for drawing, but did require a method of communicating from a remote device to the host by using the touch sensor). We used a MOSFET as the switch between the tip of the device and the body of the device (which was connected to the human).

    1. Isolation of the contacts……

      since the display is capacitive, it requires very little to trigger it
      I guess they tried other methods, but then found the results were unpredictable, so they went to a hardware guaranteed solution, that would work with ALL sizes of display.

      1. That does not explain it at all. A finger is the same size regardless of the size of the display, so the display is designed with an appropriate sensor for its size.

        A MOSFET can electrically isolate two parts of a circuit in the same way as a relay (I know, I did this with touch sensors).

        So, why use a relay? Clicking it on and off rapidly will wear it out.

      2. I experimented with this a while ago and documented here. I found that a relay worked most reliably. @Andrew Were you using the MOSFET to short between a human and the screen or circuit ground and the screen? Have you documented your circuit anywhere? Thanks.

  4. First off- any reverse engineering writeups have Hacking merit when they enable derivative Hackery. Several points scored for such work by Rob. Adding functionality is a Hack stand alone even if there’s not any “How It Works” info for the base device’s unmodded form.

    Some design parameters of high volume low ticket average gear are set by juggling price to elegance ratios. Or just going for Last Resort FIRST work as “Yeah- it works, It’s under budget- ship it” gets designers their next gig:} By embracing “Good Enough” as just that.

    And it gets us Hackerdom folks another vector for making new magic with. Large multitouch tables for example. Envision a mousebot able to toggle it’s “finger” on the table?

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