The NRF24L01 is a small, very low-power, easy-to-use wireless transceiver that operates in the 2.4 GHz range. It can send and receive data but cannot do so at the same time. This makes its cost cheaper and its operation very simple and robust. You can use it in any project that needs to send and/or receive data wirelessly without complications. The ideal is to have a partner and make a complete link. It is fully compatible with Arduino.
The NRF24L01 is powered by 3.3V and its data control is done by the SPI bus, the pins tolerate 5V levels so you can connect it directly to your favorite 5V microcontroller without the need for any level converter. You can also use it with a Raspberry Pi. Below you will find a library for that.
It has a built-in antenna, but don't expect much range. The normal about 10 or 20 meters approximately indoors (beware of the walls!) and in the open field just a little more.
Characteristics:
Chip NRF24L01
Frequency: ISM 2.4 GHz
Modulation: GFSK with automatic gain control
Data Control: SPI
Speed: 250kbps, 1Mbps and 2Mbps (configurable)
Power supply: 1.9V to 3.6V
Consumption: Transmission: 11.3mA, reception: 13.5mA @ 2Mbps, 900nA in power down and 26uA in standby.
Interrupt IRQ pin for reception