| 摘要 |
An apparatus and method for scanning a triangular or trapezoidal key matrix for data input by depressing keys of a keypad. The key matrix allows an increased number of keyswitches to be provided on the key matrix while reducing the number of I/O ports on the I/O interface. The apparatus includes an I/O interface connecting the keypad to the CPU. The keypad I/O interface is provided with m I/O ports, where m is plural integer. Through detecting the voltage levels of these I/O ports, the CPU is able to determine which key on the keypad is being depressed. A triangular key matrix is constructed with a set of m code lines and at least one auxiliary code line arranged in such a way as to form a triangular array of mx(m+1)/2 cross-points. Each cross-point is provided with a keyswitch associated with a key on the keypad. The m code lines are connected correspondingly to the m I/O ports on the keypad I/O interface. In another embodiment, a trapezoidal key matrix is constructed with m code lines and two auxiliary code line including a ground line and a power line arranged in such a way as to form an m-by-(m+1) trapezoidal array of mx(m+3)/2 cross-points. The method according to the invention is performed by the apparatus to determine which key is being depressed and carry out various actions according to the function of the key being depressed.
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