键盘扫描

矩阵键盘接口（反转法）：

使用双向接口，行列交叉点连键，行列数接近。

行出低，检列码；列出低，检行码；键值等于行列码之和。-Keyboard scan matrix keyboard interface (inversion method): Use two-way interface, the ranks of the intersection with keys, the number of close ranks. Line out is low, check out code　listed low, check the line code　the key code is equal to the sum of the ranks.