Patent ID: 7519436

Claim:
A button device comprising a voltage source and a plurality of buttons, said voltage source is connected to a terminal of each button for providing electric power, the button device comprising: a charging module comprising a plurality of charging resistors respectively coupled to another terminal of each button for providing a plurality of charging paths, wherein at least one charging path is connected when at least one button is pressed; a loading capacitor coupled to the charging module for obtaining the electric power from the connected charging path to generate a charged signal; a control module comprising a plurality of control capacitors respectively coupled to another terminal of each button and a terminal of each charging resistor for sending a control signal through a connected control capacitor when the button is pressed to generate the control signal; a micro controller unit (MCU) coupled to the control module and the charging module for receiving the control signal to calculate a charging time and determining which button is pressed according to the charging time; wherein the control module is coupled to a general input/output (GIO) pin of the MCU, the GIO pin is in an input mode, and the MCU receives an interrupt through the GIO pin to calculate the charging time when the control signal is generated and the MCU stops calculating the charging time when the charged signal reaches a first predetermined voltage, and wherein each charging resistor has a different resistance corresponding to a different charging time; the button number, the charging resistor number, and the control capacitor number are equal to three; the resistance of a first, second, third charging resistors of the charging module are respectively equal to R, 2R, and 4R, wherein R is a constant; the capacitance of the loading capacitor is equal to C, wherein C is a constant; and a first, second, and third buttons corresponding to different charging path are respectively equal to RC, 2RC, and 4RC.