While interfaces, such as Ethernet or USB, send data as a serial stream, the term serial port usually identifies hardware compliant to the RS-232 or RS-422/RS-485 standard.

In modern computers, serial ports have been replaced by USB-to-serial devices because an RS-232 port can be easily emulated by a dedicated USB device (this is exactly what our BeagleBone Black does by default, as already seen in The first login section of Chapter 1, Installing the Developing System). However, the standard serial port's hardware still exists in the embedded and industrial world. The reason is quite simple: because the serial ports are easy to use and easy to implement (the hardware and software are light and do not engage the CPU too much). So, serial ports are still used in applications, such as industrial automation systems and remote monitoring or in some scientific instruments. It's quite easy to find industrial devices (not only a normal peripheral but just a complete...