There is also a video on YouTube for this article: Arduino NRF24L01 (German)

NRF24L01 & Arduino

The radio module NRF24L01 is a further development of the traditional NRF24. The new version is also known as nRF24L01 + PA + LNA. This version has a powerful amplifier and an external antenna connector, where ranges of up to 1000 meters should be possible. The module in this article is operated with an Arduino Uno Board. The first module works as a transmitter and the second one works as a receiver. But each module can send and receive, so a transmission in both directions is possible.

Connect NRF24 to your Arduino

The module uses the SPI interface as connection to the Arduino board. In addition, two more pins (CSN & CE) are necessary.The module does not require any additional power supply, but it must be connected to the 3.3 volt pin. Do not power the module with 5 volts, because it can damage it!Data lines can be connected directly to the module without a voltage reduction.

Software

The sender and receiver have their own software. The configuration and pin assignment is the same on both sides. The parameter that is transmitted can be sent as a string and will also be printed as a string on the receiver side. With a software extension, the string can be split. This makes it easy to exchange several parameters in one transmission. The example code is very simplified and shows the minimum settings for a data exchange. In addition, the NRF24 Library is needed.

Code for Transmitter

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
const byte rxAddr[6] = "00001"; //TX adress (Same as on RX)
int counter = 0; //Count TX (Only for demo example)
RF24 radio(8, 9); //Define Radio (CE-PIN,CSN-PIN)
void setup() {
while (!Serial);
Serial.begin(9600);
radio.begin();

radio.setPALevel(RF24_PA_MAX); // Transmit Power (MAX,HIGH,LOW,MIN)
radio.setDataRate( RF24_250KBPS ); //Transmit Speeed (250 Kbits)
radio.setRetries(15, 15);
radio.openWritingPipe(rxAddr);
// Disable Receiver
radio.stopListening();
}
void loop() {
counter++;
String str = "Send Counter: "; 
str += String(counter);

int str_len = str.length() + 1; 
char char_array[str_len];
str.toCharArray(char_array, str_len);
radio.write(&char_array, sizeof(char_array));

Serial.print("Actual Transmission: ");
Serial.println( char_array );
delay(250);
}

Code for Receiver

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
RF24 radio(8, 9); //Define radio (CE-PIN,CSN-PIN)
const byte rxAddr[6] = "00001"; //RX adress (Same as on TX)
String received_data;
void setup()
{
// Start the serial
Serial.begin(9600);
Serial.println("NRF24 Receiver");
radio.begin();
radio.setPALevel(RF24_PA_LOW); // Transmit Power (MAX,HIGH,LOW,MIN)
radio.setDataRate( RF24_250KBPS ); //Transmit Speeed (250 Kbits)
radio.openReadingPipe(0, rxAddr);
radio.startListening();

}
void loop()
{
if (radio.available())
{
char text[100] = {0}; //Buffer
radio.read(&text, sizeof(text));
received_data = String(text);
Serial.println(received_data);
delay(20);
} 
}

Maximum range

The modules are very powerful. It should be possible to transmit data of several hundred meters. For this we will make a range test with the modules. In our first test, we have already done a clean data transfer at a distance of 130 meters (free view).