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In this tutorial, I am going to show you guys how to use this transceiver module to add wireless communication between two or more Arduino boards. I will be using this module for many of my upcoming home automation projects. Bang Problem solved..

What Is a NRF24L01 RF Transceiver Module?

So far, I have always used WiFi for wireless communication between microcontrollers. While this is easy enough to do, it is not exactly suitable for battery operated nodes. WiFi modules consume a lot of current when transmitting data plus they also have a slight delay when initiating the transmission as the module has to first connect to the WiFi network.

After getting crippled by the abilities of my wireless router, I found this cheap, very popular and widely used “RF Transceiver Module” which you can hook up to any microcontroller (MCU). This module is called a RF transceiver because a single module can work both as a transmitter and a receiver.

- The module operates at a frequency of 2.4GHz, which is one of the ISM band which means it is open to use in most of the countries around the World.
- Data transfer rate is between 250kbps to 2Mbps baud.
- Power consumption? This module is designed for ultra low power wireless applications. It has 2 power saving modes operating at 22uA Standby-I mode and 900nA in power down mode - which makes these modules suitable for battery operated nodes. The high air data rate combined with two power saving modes makes the nRF24L01 module very suitable for ultra low power designs. The power consumption of this module is just around 12 milliamps during transmission (TX) which is even lower than a single led.
- Operating voltage is between 1.9V to 3.6V. All other pins on this board are 5V tolerant making it easy to connect to an Arduino without using a logic level converter. It has an integrated (on chip) voltage regulator.
- The Range of this module as per its datasheet is 100m but it works up to 50 to 60 meters in real world conditions.
- The module has 125 independent RF channels giving the possibility to have a network of “125 independently working modems” in one place. Each channel can have up to “6 addresses or 6 data pipes” or in other words, each unit can communicate with up to 6 other units at the same time (1:6 star networks).
- The module is configured and operated through a Serial Peripheral Interface (SPI).
- It uses Enhanced ShockBurst™ for automatic packet assembly and timing, automatic acknowledgement and retransmission of packets. Enhanced ShockBurst™ enables the implementation of ultra low power, high performance communication with low cost host microcontrollers. The features enable significant improvements of power efficiency for bi-directional and uni-directional systems, without adding complexity on the host controller side.

The module used in this video has an in-built PCB antenna making it compact. However, you can also buy a variant that supports an external antenna allowing much higher range of about 1000M in line of sight.

NRF24L01 Pinout
Now, lets have a look at the pinouts and specifications of the NRF24L01 module:

- GND: is the Ground Pin. It is placed inside a square for easy identification.
- VCC: supplies power to the module. Voltage can range from 1.9v to 3.9v. So, you can connect it directly to the 3.3V pin of our Arduino. Remember connecting it to a 5V pin will likely destroy your nRF24L01+ module!
- CE: (Chip Enable) is an active-HIGH pin. When selected the module will either transmit or receive, depending upon which mode it is currently in.
- CSN: (Chip Select Not) is an active-LOW pin and is normally kept HIGH. When this pin goes low, the module begins listening on its SPI port for data and processes it accordingly.
- SCK: (Serial Clock) it accepts clock pulses provided by the SPI bus Master.
- MOSI: (Master Out Slave In) It is SPI input to the module. It is used to receive data from the microcontroller.
- MISO: (Master In Slave Out) It is SPI output from the module. It is used to send data to the microcontroller.
- IRQ: It is the interrupt pin that alerts the master when new data is available to process.

In order to get this working, we need two such NRF24L01 Modules and two Arduino Boards. For this tutorial I am going to use 2 Arduino Nanos.

Just remember, we cannot use a breadboard with these modules because the pin spacing on these modules are not enough to place it in the middle and if you place it anywhere else, then you will end up shorting the pins. This means that you will either have to solder the wires directly to the modules or use some sort of jumper cables.

The connection is exactly the same on both the transmitter and receiver end.

Connect the GND pin to -ve and VCC pin to 3.3v pin of Arduino. The signals generated by these modules are very sensitive to power supply noises. So, adding a decoupling capacitor (anything from 10uF to 100uF) across the power supply line is always a very good idea.

Then connect the CSN pin to D8, CE to D9, MOSI to D11, MISO to D12, and SCK to D13 pin of the Arduino.

Since the nRF24L01+ module requires a lot of data transfer, it will give the best performance when connected to the hardware SPI pins on the microcontroller. Note that each Arduino board has different SPI pins that must be connected accordingly. Have a look at the table onscreen for quick understanding.

For this tutorial I am going to use the “TMRh20/RF24OSI Layer-2 driver for nRF24L01 on Arduino & Raspberry Pi/Linux Devices. You can download the library from the link provided in the description below:”

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