Making Embedded Systems

Chapter 6. Communicating with Peripherals

We’ve investigated what goes on inside your processor during the course of this book. Now, before you can build a system, we need to consider what goes on in other components. Ultimately, the information you need is in datasheets, so if you’re comfortable extracting information from them, you might be able to skip the first two-thirds of this chapter (which looks at an overview of some common peripherals’ communication methods). The last third is more software-oriented, offering strategies for making peripherals and communication methods work well together. Don’t skip that part.

The Wide Reach of Peripherals

A peripheral is anything outside your processor that the processor communicates with. Peripherals come in all shapes and flavors. Because your processor has direct access to memory, it barely counts as a peripheral (though it can be outside your chip). Sensors tell your system about its environment, actuators act upon the environment, and displays interact with users.

I’m going to mention the most obvious of each of these so you get some ideas for your options. However, don’t let my lack of creativity limit your ideas. And if you can’t find what you want, wait 6 or 18 months and someone will come along with it (yay for I²C tricolor LEDs!).

External Memory

We’ve already looked a bit at memory and how it is classified into volatile memory (lost when the system turns off) and nonvolatile memory (retained through power cycles). RAM is the most ...