将一个键控电阻分压器与ADC相连接,就能构成简单而且便宜的键盘编码器(图1)。这类电路特别适用于μC上带集成ADC部件的嵌入系统。为了达到键间最佳噪声容限,对电阻器要精心挑选,以获得均值的分压电平。为了满足图1所示电路的这种要求,必须用一套阻值各不相同但却是专门规定的电阻 Connecting a keying resistor divider to the ADC makes for a simple and inexpensive keyboard encoder (Figure 1). This type of circuit is particularly suitable for embedded systems with integrated ADC components on the μC. In order to achieve the best noise margin between the keys, the resistor should be carefully selected to obtain a mean voltage level. In order to satisfy such a requirement of the circuit shown in FIG. 1, it is necessary to use a set of resistances which are different but which are specified