Greendicator: Enabling Optical Pulse-Encoded Data Output from WSN for Display on Smartphones

Greendicator is an indicator system that enables wireless embedded sensing systems to output data encoded as LED pulses to be decoded and viewed on smart phones. The transmitter encodes the message to be displayed in the form of modulated light pulses emitted with an existing visible-light LED or other light-emitting devices such as IR, laser diode, or light reflector. The receiver uses a camera-equipped smart phone to sense the light pulses and to decode the original message. Greendicator can be extended using the camera´s built-in flashlight as an acknowledgement to enable success communication. To develop the real-time decoding system, we apply GPU on the smart phone to process the image frames. An API is provided for programmers to incorporate Greendicator in their systems by simple function calls. Experimental results show the Greendicator can be a valuable mechanism for supporting existing RF-based networks while occupying a small memory footprint.