A Fine Line Between Art and Tech

Touchscreens and mice are fine as far as they go, but when extreme precision is needed they aren’t going to cut it. Graphic artists working on digital creations, in particular, are sorely aware of the limitations of traditional input devices. When working on a sketch, precise positioning of the drawing tool is absolutely essential. Furthermore, artists also vary the pressure they put on the tool to control the thickness and intensity of the elements that are drawn. Without this type of control, the work that they produce will tend to look amateur.

Fortunately, better input devices exist for those with special use cases that require them. Electromagnetic resonance (EMR) drawing tablets are especially well-suited for applications that seek to reproduce the experience of using a traditional pen or pencil. These devices can be standalone input pads, or they can be positioned behind the screen of a tablet or other computing device. In either case, the EMR tablet receives and detects electromagnetic waves emitted at regular intervals by a digital pen. From this data, precise X/Y coordinates and pressure measurements can be derived.

Hardware hacker Yukidamayaki recently created a custom EMR tablet called Patchouli. Sure, there are a number of commercial options available on the market, but some people are very picky about their tools. Yukidamayaki happens to be one of those people, and if you are as well, Patchouli is open source, so you can build your own… or use it as a base for your own custom design.

The device was constructed entirely from commercially available parts, and includes the coil array and RF front end necessary for operation. Yukidamayaki also developed the digital signal processing algorithms needed to translate the EMR measurements into inputs. As far as pens are concerned, Patchouli is compatible with virtually any off-the-shelf option that you would like to use.

In a series of demonstrations, Yukidamayaki showed just how accurate the drawing tablet is. When the build was complete, it was even integrated into an existing laptop, turning the screen into a high-precision input device. It looks like a digital artist’s dream come true — but of course it will take some serious skill in electronics to build and install the device for yourself.

The software and KiCad design files have been made available for download for anyone that is interested in the project. There is also extensive documentation that explains the theory behind the technology and the details of this specific implementation. Even if you are not planning to build a copy of Patchouli, the documentation is still worth a read — it is a treasure trove of information on the subject.