A card exhibiting multiple linear arrays of sensors are provided to detect a presence and movement of an external object (e.g., a read-head of a magnetic stripe reader). Each sensor of each array of sensors may be independently connected to a dual port of a processor so that the processor may determine a direction in which the card is swiped through a magnetic stripe reader. A portion of sensors of each array of sensors may be shared by a portion of inputs and/or outputs of a single port of a processor. Sensors may be cross-coupled to a single processor port so that forward and reverse directions of a card swipe may nevertheless be detected by a single-port processor of a card.