Back in January, we took a look at the new Genuino 101 - Arduino 101 for those in the US - from Intel and Arduino, which serves as demonstration of Intel Curie module's capabilities and as a powerful Bluetooth-equipped Arduino development board. There's no denying that it's a neat bit of kit, but compared to devices like the Arduino Leonardo and Uno it comes at a premium - and what if you only need Bluetooth support, rather than the extra sensors, memory, and processing power available from the Curie module? The answer's simple: add Bluetooth to your existing Arduino board.
The makers over at TechDepot Egypt have published an Instructable that'll help you do exactly that, using the popular and low-cost HC-05 Bluetooth module. In particular, it covers an important aspect of connecting the HC-05 to an Arduino: it uses 3.3V logic rather than 5V, which means a direct connection to the TX pin on an Arduino is potentially enough to fry the module. While a bi-directional level shifter is the perfect solution to the problem, this adds board space and cost; as an alternative, TechDepot Egypt's method is to use a pair of cheap resistors to drop the voltage down to safe levels.
While the HC-05 uses full-fat Bluetooth communications, rather than the Internet of Things (IoT) oriented Bluetooth Low Energy of the Genuino 101, its overall power draw is low and it provides an easy way to interface Arduino projects with a smartphone, tablet, or other Bluetooth-equipped computing device. Better still, it's compatible with Saggaf Arsyad's VirtualShield package, which allows your Arduino to tap into the sensors built into an Android smartphone or tablet - duplicating much of the functionality of the Genuino 101.
The HC-05 Bluetooth module is an excellent interface for communicating with your mobile. It has a great data transfer rate and [is] very easy to implement.