USB and Serial Communication - Exploring Arduino: Tools and Techniques for Engineering Wizardry - page 109

NOTE Tolearnallaboutserialcommunication,checkoutthistutorial:
www.jeremyblum.com/2011/02/07/arduino-tutorial-6-serial-
communication-and-processing/ .Youcanalsofindthistutorialonthe
Wileywebsiteshownatthebeginningofthischapter.
To begin, you need to understand the differences between serial and USB.
Depending on how old you are, you might not even remember serial (or techni-
cally, RS-232) ports, because they have been primarily replaced by USB. Figure 6-1
shows what a standard serial port looks like.
Figure 6-1: Serial port
The original Arduino boards came equipped with a serial port that you con-
nected to your computer with a 9-pin serial cable. Nowadays, few computers still
have these ports, although you can use adapters to make DB-9 (the type of 9-pin
connector) serial ports from USB ports. Microcontrollers like the ATMega328P
that you find on the Arduino Uno have one hardware serial port. It includes a
transmit (TX) and receive (RX) pin that can be accessed on digital pins 0 and
1. As explained in the sidebar in Chapter 1, “Getting Up and Blinking with the
Arduino,” the Arduino is equipped with a bootloader that allows you to pro-
gram it over this serial interface. To facilitate this, those pins are “multiplexed”
(meaning that they are connected to more than one function); they connect,
indirectly, to the transmit and receive lines of your USB cable. However, serial
and USB are not directly compatible, so one of two methods is used to bridge