Programming Embedded Systems, 2nd Edition

Chapter 13. Extending Functionality

Kramer: It’s just a write-off for them.Jerry: How is it a write-off?Kramer: They just write it off.Jerry: Write it off what?Kramer: Jerry, all these big companies, they write-off everything.Jerry: You don’t even know what a write-off is.Kramer: Do you?Jerry: No. I don’t.Kramer: But they do and they are the ones writing it off.

—the television series “Seinfeld,” episode “The Package”

In this chapter, we introduce additional hardware and software technologies that you may encounter in embedded systems. We begin with a look at a pair of chip interconnection buses called I²C and SPI. Next we introduce programmable logic, including FPGAs. And finally, we take a look at adding a TCP/IP network.

Common Peripherals

As you work on more and more embedded systems, you will come across different peripherals that you will have to use. In this section, we take a look at some of the common embedded peripherals that you will likely encounter. Sometimes it is necessary to implement these protocols entirely in software (see the sidebar “Serial Bit Banging” later in this chapter).

Serial buses can be either asynchronous or synchronous. In an asynchronous serial connection, the data is sent without using a common timing clock signal. To align the receiver with the sender, there is some sort of start condition to signify when the transmission begins, and a stop condition to indicate the end of transmission. A synchronous serial connection typically ...