Keypad with 1-bit capacitive touch sensing analog front end with sparse multi-touch detection

摘要

A capacitive touch keypad may receive a touch by a conductive object to one or more keys of the keypad, in which the keys each have a separate capacitive key electrode. The touched locations may be determined by precharging a pseudo-randomly selected set of key electrodes a number (M) of iterations while the keyboard is being touched, producing a sense voltage for each iteration by coupling all of the key electrodes to a reference capacitor, producing a 1-bit sense measurement for each iteration by comparing the sense voltage to a reference voltage to form a set of M 1-bit sense measurement, and by applying a modified binary iterative hard threshold (BIHT) algorithm to the set of M 1-bit sense measurements, in which only the non-zero locations of the solution are monitored in each iteration.

主权项

1. A method for operating a capacitive touch keypad, the method comprising:
receiving a touch by a conductive object to one or more keys of the keypad, in which the keypad has a plurality of keys that each have a separate capacitive key electrode; precharging a pseudo-randomly selected set of key electrodes a number (M) of iterations while the keyboard is being touched; producing a sense voltage for each iteration by coupling all of the key electrodes to a reference capacitor; producing a 1-bit sense measurement for each iteration by comparing the sense voltage to a reference voltage to form a set of M 1-bit sense measurements; and determining each touched key location by applying a modified binary iterative hard threshold (BIHT) algorithm to the set of M 1-bit sense measurements, in which only the non-zero locations of the solution are monitored in each iteration.