“Having two or more Arduino boards be able to communicate with each other wirelessly over a distance opens lots of possibilities like remotely monitoring sensor data, controlling robots, home automation and the list goes on. And when it comes down to having inexpensive yet reliable 2-way RF solutions, no one does a better job than nRF24L01+ transceiver module from Nordic Semiconductor.
nRF24L01+ (plus) transceiver module can often be obtained online for less than two dollars, making it one of the most inexpensive data communication options that you can get. And best of all, these modules are super tiny, allowing you to incorporate a wireless interface into almost any project.
Hardware Overview
Radio Frequency
The nRF24L01+ transceiver module is designed to operate in 2.4 GHz worldwide ISM frequency band and uses GFSK modulation for data transmission. The data transfer rate can be one of 250kbps, 1Mbps and 2Mbps.
What is 2.4 GHz ISM band?
2.4 GHz band is one of the Industrial, Scientific, and Medical (ISM) bands reserved internationally for the use of unlicensed low-powered devices. Examples are Cordless phones, Bluetooth devices, near field communication (NFC) devices, and wireless computer networks (WiFi) all use the ISM frequencies.
Power consumption
The operating voltage of the module is from 1.9 to 3.6V, but the good news is that the logic pins are 5-volt tolerant, so we can easily connect it to an Arduino or any 5V logic microcontroller without using any logic level converter.
The module supports programmable output power viz. 0 dBm, -6 dBm, -12 dBm or -18 dBm and consumes unbelievably around 12 mA during transmission at 0 dBm, which is even lower than a single LED. And best of all, it consumes 26 µA in standby mode and 900 nA at power down mode. That’s why they’re the go-to wireless device for low-power applications.
SPI Interface
The nRF24L01+ transceiver module communicates over a 4-pin Serial Peripheral Interface (SPI) with a maximum data rate of 10Mbps. All the parameters such as frequency channel (125 selectable channels), output power (0 dBm, -6 dBm, -12 dBm or -18 dBm), and data rate (250kbps, 1Mbps, or 2Mbps) can be configured through SPI interface.
The SPI bus uses a concept of a Master and Slave, in most common applications our Arduino is the Master and the nRF24L01+ transceiver module is the Slave. Unlike the I2C bus the number of slaves on the SPI bus is limited, on the Arduino Uno you can use a maximum of two SPI slaves i.e. two nRF24L01+ transceiver modules.”