There are various wireless communication technologies used in building IoT applications and RF (Radio Frequency) is one of them. nRF24L01 is a single-chip radio transceiver module that operates on 2.4 - 2.5 GHz (ISM band). This transceiver module consists of a fully integrated frequency synthesizer, a power amplifier, a crystal oscillator, a demodulator, a modulator, and Enhanced ShockBurs protocol engine. Output power, frequency channels, and protocol setup are easily programmable through an SPI interface.

Components Required

Arduino Uno (2)

nRF24L01 (2)

16*2 LCD

LCD I2C Module

DHT11 Sensor

NRF24L01 Transceiver Module Circuit diagram

The circuit diagrams for Arduino nRF24L01 based transmitter and receiver are given below. Here, we are sending the temperature and humidity values wirelessly from one Arduino to another using the nRF24L01 module. To get the temperature and humidity values, we are using the DHT11 sensor that is connected to the transmitting side Arduino. Transmitting Arduino will get temperature and humidity values from DHT11 and then sends it to another Arduino via the nRF24L01 module. These humidity and temperature values will be displayed on 16*2 LCD connected to the receiver side, Arduino.

Interfacing nRF24L01 with Arduino UNO - Transmitting Side

The transmitter side consists of an Arduino UNO, nRF24L01 module, and DHT11 sensor. Interfacing of the Arduino UNO with nRF24L01 and DHT11 is shown below. Arduino continuously gets data from the DHT11 sensor and sends it to the nRF24L01 Transmitter. Then the nRF transmitter transmits the data into the environment.

nRF24L01 Arduino Sender and Receiver Testing

Once the hardware and program are ready, upload both nRF24L01 transmitter and receiver codes in both Arduino modules. The transmitter module will send the temperature and humidity values to Receiver Module. And the receiver module will display it on its 16x2 LCD as shown below

This is how you can use nRF24L01 as a wireless communication medium between two Arduinos.

Code

Transmitter Side

#include <SPI.h>

#include <nRF24L01.h>

#include <RF24.h>

#include "DHT.h"

const uint64_t pipeOut = 0xE8E8F0F0E1LL; 

#define DHTPIN 3

#define DHTTYPE DHT11 

DHT dht(DHTPIN, DHTTYPE);

RF24 radio(9, 10); // CN and CSN pins of nrf

struct MyData {

 byte h;

 byte t;

};

MyData data;

void setup()

{

 Serial.begin(9600); 

 dht.begin();

 radio.begin();

 radio.setAutoAck(false);

 radio.setDataRate(RF24_250KBPS);

 radio.openWritingPipe(pipeOut);

}

void loop()

{

 data.h = dht.readHumidity();

 data.t = dht.readTemperature();

 if (isnan(data.h) || isnan(data.t)){

  Serial.println(F("Failed to read from DHT sensor!"));

  return;

 }

 Serial.print("Humidity: ");

 Serial.print(data.h);

 Serial.print("Temperature: ");

 Serial.print(data.t);

 radio.write(&data, sizeof(MyData));

}

 

Receiver Side

#include <SPI.h>

#include <nRF24L01.h>

#include <RF24.h>

#include <Wire.h> 

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const uint64_t pipeIn = 0xE8E8F0F0E1LL; 

RF24 radio(9, 10);

struct MyData {

 byte h; 

 byte t;

};

MyData data;

void setup()

{

 Serial.begin(9600); 

 radio.begin();

 lcd.begin();

 lcd.home();

 lcd.backlight();

 lcd.clear();

 radio.setAutoAck(false);

 radio.setDataRate(RF24_250KBPS);

 radio.openReadingPipe(1, pipeIn);

 radio.startListening();

 //lcd.println("Receiver ");

}

void recvData()

{

 if ( radio.available() ) {

  radio.read(&data, sizeof(MyData));

  }

}

void loop()

{

 recvData();

 Serial.print("Humidity: ");

 Serial.print(data.h);

 lcd.setCursor(0,0);

 lcd.print("Humidity:"); 

 lcd.print(data.h);

 lcd.print("%");

 lcd.setCursor(0,1);

 Serial.print("Temperature: ");

 Serial.print(data.t);

 lcd.print("Temperature:");

 lcd.print(data.t);

 lcd.print(" C"); 

 //Serial.print("\n");

}