| 摘要 |
A method and apparatus for calibrating a resistive ladder switching matrix (110) coupled to a keypad in a portable electronic device having a housing with a cover (120) that may be positioned in an open state or a closed state. A first contact (140) of a calibration element (115) is coupled to a reference voltage VREF and a second contact (142) of t he calibration element is coupled to ground by moving the cover (120) from the open state to the closed state. When the first contact (140) of the calibration element is coupled to the reference voltage and the second contact (142) of the calibration element is coupled t o ground, a calibration resistance across the calibration element (115) is determined. The calibration resistance may correspond to an input impedance of the resistive ladder switching matrix (110) when no buttons associated with the keypad are depressed. Signals from the resistive ladder switching network (110) are calibrated when the cover is in the closed state in accordance with the calibration resistance.< /SDOAB>
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