A versatile and mobile keyboard and a highly energy efficient keyboard scanning method are provided. The keyboard may be used with a variety of mobile devices such as PDAs, cellular phones, and tablet PCs, through various interfaces such as an IR, USB, or Bluetooth™ interface. In particular, an IR head assembly is provided that includes an IR head, a movable arm on which the IR head is mounted, and a connector for attaching to a docking structure. The docking structure may be attached to a keypad, which is electrically coupled to the IR head for transmitting keystroke data through the IR head. When a mobile device is docked on the docking structure, the arm in the IR assembly may be moved to an optimal distance from the IR port of the mobile device to ensure high communication performance between the keyboard and the mobile device. An energy efficient keyboard scanning method utilizes higher-valued pull-up resistors for energy conservation. The keyboard scanning method includes a charging step to charge stray capacitance associated with the keys. The keyboard scanning method can also be operated at a variable scanning frequency.