Apparatus and method for selectively driving a piezo transducer

An apparatus for controlling a device having a touch sensor, comprising:

• a piezo transducer for detecting a pressure pattern applied to the sensor;
• a comparator coupled to the transducer;
• and
• a pressure pattern recognition circuit coupled to a comparator output of the comparator, the circuit being configured to:
• determine whether the pressure pattern satisfies a predetermined condition;
• and
• in response to the pressure pattern satisfying the predetermined condition, generate an output signal;
• a switch coupled to and selectively connecting the transducer to one of (i) a logic circuit and (ii) an oscillator, wherein:
• the transducer operates as a pressure pattern detector in response to being connected to the logic circuit, wherein the logic circuit provides a signal value corresponding to a logic value, thereby grounding a bottom lead of the transducer;
• and the oscillator provides an oscillating signal, thereby increasing a drive voltage to the transducer;
• and
• the transducer operates as an alarm generator in response to being connected to the oscillator;
• an inverter connected between the switch and a bottom lead of the transducer, wherein:
• the inverter is configured to transmit a ground signal to the transducer to permit the transducer to operate as the pressure pattern detector;
• and
• the inverter is configured to transmit an oscillating signal to the transducer to permit the transducer to operate as the alarm generator;
• a tri-state buffer coupled to a top lead of the transducer, wherein:
• in response to the tri-state buffer being set to a high impedance state, the transducer is permitted to operate as the pressure pattern detector;
• and
• in response to the tri-state buffer being set to a low impedance state, the transducer is permitted to operate as the alarm generator.