描述

使用 Galileo II 和 ANSI C，演示如何驅動 MCP23017 IO 擴展器 16 個通用輸出，它們本身驅動四個 74HC4511 七段顯示驅動器。

The 74HC4511 accepts as inputs a 4 bit binary encoded decimal value. This value is interpreted as a single digit, and the 74HC4511 converts this value to provide output to the seven individual segments to display the digit.

The C code demonstrates how to interact with the MCP23017 using the MRAA I2C interface. This interaction is composed of two bytes, with each byte driving the two general purpose IO groups. Each byte is composed of eight bits - two four bit groups. Each four bit group represents a digit to the 74HC4511.

C 代碼進一步演示了結構的使用 - 包含四個數字值，并且對于每個數字值，都有一個標志，指示是啟用特定的七段顯示，還是將其全部清空。該代碼進一步展示了 C 位運算符的強大功能以及操作位的簡單性。最后，對于新的 C 編碼器，干凈的代碼演示在函數調用中使用顯式值，并避免使用全局變量。

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