iPhone Proximity Sensor

Question

Can the iPhone SDK take advantage of the iPhone\'s proximity sensors? If so, why hasn\'t anyone taken advantage of them? I could picture a few decent uses.

For examp

Answer 1

Those proximity sensors are basically a matrix of conductors. The vertical "wires" are tracks on one side of a thin sheet of insulator, the horizontal ones are on the other side. The intersections function as capacitors. Your finger carries an electrostatic charge, so capacitance of each junction varies with proximity. FETs amplify the signal and biasing sets a threshold. In practice the circuit is more complex than that because it has to detect a relative change and reject noise.

But anyway, what the sensor grid tells you is that a field effect has been sensed, and that field effect is characteristic of object about the size of a fingertip and resting on the surface of the display. The centroid of the capacitive disturbance is computed (probably by hardware) and the coordinates are (presumably) reported as numbers on a port most likely brought to the attention of the device OS by an interrupt. In something as sexy as an iPhone there's probably a buffer of the last dozen or so positions so it can work out direction and speed. Probably these are also computed by hardware and presented as numbers on the same port.