1. A sensing device comprising: an image sensor for capturing images of coded data disposed on a surface; a framestore for storing frames of the captured image as image data; subsampling means for subsampling the stored image date to generate subsampled image data; and an image processor for processing the subsampled image data to generate interaction data based on the sensed coded data and indicative of interaction of the sensing device with the surface, wherein the image processor is integrated on a monolithic integrated circuit, the monolithic integrated circuit including a first subsampled framestore for storing the subsampled image data based on image data from the framestore.