Bluetooth communications are also based on the 2.4 GHz ISM RF band. Bluetooth was originally invented and developed by Ericsson. The fundamental reason for inventing Bluetooth Technology was to provide a wireless alternative for RS-232 based cables and wires. Since then the Bluetooth protocol has come a long way and is primarily used over short distances (less than 30 feet) for:

• Establishing wireless connections between two hosts
• Exchanging data between two connected (paired) hosts

There are many varieties of Bluetooth chips available on the market today. Each variety is designed for meeting special purposes such as range, and special capabilities such as voice streaming. In this chapter, we will learn how to use Bluetooth communication by using the HC-05 Bluetooth chip. The HC-05 is a very commonly used Bluetooth chip with a synchronous transmission speed of 1 mbps and an Asynchronous transmission speed of 160 kbps. It can go upto a maximum of 2.1 mbps.

The HC-05 is a dual purpose module and can be configured as both a slave and a master. In Bluetooth communications we always create a pair of devices - one is a master and the other is a slave. There are some other varieties of the HC series Bluetooth module available in the market such as HC-06. The HC-06 can be used only as a slave only module. The HC-05 module is a classic Bluetooth module. There is another category of Bluetooth modules that consume very low energy, such as an HM-10 module, and are known as Bluetooth Low Energy (BLE) module. In this chapter, we will focus on the HC-05 which is based on the classic Bluetooth module.