Activating a Tablet with Hardware

For the past few weeks, CTT has been getting an installation together for the TIFF DigiPlaySpace that will allow children to physically trigger an animation on a tablet. We’re delighted to be working with the team at Sago Sago on this project.

Creating physical triggers to start/ stop an animation is a fairly inconsequential task – you open a button sketch in the Arduino IDE and plug whatever hopped-up equivalent of 2 buttons you have into some pins. The challenging part about this project is communicating to a tablet. Fortunately, this is a subject I explored way back in 2013 at FITC Screens: Free Range Arduino.

A good solution is one that can be used with any of the many options for creating a mobile application, so we started exploring FSK and using the touch screen.

FSK (Frequency Shift Keying) is when you use audio signals to send data – in this case, we’re sending the data through the audio jack and generating the audio using an arduino. At the very least, we can keep sending audio until we want an animation to start and then stop (or vice versa). Any mobile/tablet application solution that has access to the microphone should work with that. If you want to get more complex than that, you can send audio signals back and forth and decode the signals to represent data – a great solution but difficult to do across multiple technologies (native, phonegap, unity, flash, OF etc). Matthew Potter actually managed to get audio out of our arduino:

Additionally, we explored using a relay and metal contacts on the screen itself. Using an arduino to control a relay we can mimic the touch behaviour of a tablet screen. By sending a recognisable signal to the screen as a “keep alive” we can cue an animation to start or stop. Once again, the difficulty is in sending and receiving viable data and decoding it – a solution needs to be used across many different technologies. This is demonstrated below:

Touchless touchscreen. #cttoronto #ctt #arduino #buyral

A video posted by blacksanta_69 (@blacksanta_69) on

The final solution, and probably the easiest, is to use a bluetooth HID device to connect as a keyboard. This can be done easily with a device like the Adafruit Bluefruit EZ-Key or a BlueSMiRF which can be used to send data to a tablet as keyboard input. By using a bluetooth keyboard, you can send full strings of data easily and it can be integrated into almost any mobile/ tablet technology quite easily.

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