Arduino Sketches: Tools and Techniques for Programming Wizardry

CHAPTER8

Wire

This chapter discusses the following functions:

• begin()
• beginTransmission()
• write()
• endTransmission()
• read()
• available()
• requestFrom()
• onReceive()
• onRequest()

The hardware needed to use the examples in this chapter includes:

• Arduino Uno x 2
• Arduino Due
• Silicon Labs Sensor EXP board

You can find the code downloads for this chapter at http://www.wiley.com/go/arduinosketches on the Download Code tab. The code is in the Chapter 8 folder and individually named according to the code filenames noted throughout this chapter.

Introducing Wire

Connection wires I²C, short for Inter-IC bus, is a serial bus designed to enable access to numerous devices. The Arduino's hardware serial bus can connect only to one device at a time, and SPI (see Chapter 7) can talk to three devices. In 1982, Philips created the I²C standard, capable of addressing hundreds of devices, using only two wires. It was first used to connect peripherals together in a television set, but since then, I²C has been used in cars, computer systems, and hobbyist electronics, to name a few. It is an easy and inexpensive way to interconnect dozens (if not hundreds) of devices on a same network.

Originally, only a few I²C devices existed, but today there are hundreds of devices. Temperature sensors, pressure sensors, accelerometers, displays, and even EEPROM memory can all be accessed by I²C, using simple reads and writes. An EEPOM device controlled by I²C is illustrated in Figure 8-1.

Figure 8-1: I²C EEPROM integrated ...