The HC-05, a Bluetooth to serial bridge, can be found for around $5 on the internet and therefore may be the cheapest way to add Bluetooth connectivity to your project. However, its default setting… ...

The HC-05 is one of a series of castellated modules (HC-06, -07, etc). the JY-MCU is a breakout board for whatever version of module happens to be soldered onto it. Report comment Reply ...