将第二MCU引入嵌入式设计

　　将第二MCU引入嵌入式设计

　　有很多理由在你的设计中添加第二个MCU，一旦你做了很多错误，就避免了。本文在考虑沿途的缺陷时考虑了参数和选项。

　　随着处理器可用的今天，品种繁多，有很多原因，你会发现它是添加新的功能引入第二单片机的应用更具成本效益的选择（MCU）或微处理器（MPU）为你的设计而不是试图一次完成所有的任务，更高性能的处理器：

　　成本：迁移到一个更高性能的系统中，微处理器可以比添加8位或16位MCU来承担额外的负载有更高的成本差异。

　　电源：而不是花费的权力，使主要应用处理器不断打开自己来执行一个相对简单的操作，如监测一个传感器银行或检查是否有一个按键被按下，一个8位处理器可以用来执行这些任务。本质上，8位处理器是一个“电源门”，它只允许主处理器在需要注意的事件发生时休眠并唤醒它。这是特别有效的电阻和表面电容式触摸屏。

　　确定性：包括计算密集型任务（如动画或音频）的用户界面（UI）功能可以强调系统的实时确定性行为。第二个MCU可以承担所有的“实时”UI责任，而不是威胁像电机控制这样的关键任务的可靠性。

　　Diversity： Many systems can benefit from a modular design. For example， a display module can be implemented with a different processor to provide additional graphics， or streaming video capabilities. By taking a modular approach， the main application code does not need to be changed to add new features to the system or to support different models.

　　Simplicity： A product line may offer a wide variety of options. For example， a product may have four screens， three keyboards， and three connectivity options. When a single processor is used， the design team has to maintain， test， and verify a separate code version for each possible variant （4x3x3=36 distinct variants）。 When a secondary processor is used to implement a new function， maintenance is required only for each option （4+3+3=10）。 Note that with the first option， the entire system needs to be tested and verified with every variant， a complex and time-consuming process. When using the second option， the main application code only needs to be verified once. Each of the options can be verified separately and with significantly less complexity.

　　Conservation of I/O： An MCU can appear to be several devices over an interface by responding to several addresses. For example， the main application processor could issue a command to turn on a fan which is intercepted by an MCU serving as a virtual hub. This is an effective way to conserve I/O on the main application processor since only one communication peripheral is required to read and control multiple devices.

　　Certification： Changing the user interface or introducing a new interface like Wi-Fi to the main system requires the entire design to be recertified for some markets. Implementing these functions as an add-on module with a separate processor simplifies the recertification process， significantly accelerating both development and time-to-market.