RF communication with nRF24L01 in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this nRF24L01 initialization code?

Consider the following Arduino code snippet initializing the nRF24L01 module. What will be printed on the Serial Monitor?

Arduino

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10); // CE, CSN pins

void setup() {
  Serial.begin(9600);
  if (!radio.begin()) {
    Serial.println("Radio hardware not responding!");
  } else {
    Serial.println("Radio initialized successfully.");
  }
}

void loop() {}

A Radio initialized successfully.

B Radio hardware not responding!

C Compilation error due to missing library.

D No output, Serial Monitor is empty.

💡 Hint

The radio.begin() returns true if the module is connected and working.

The code initializes the radio and checks if it begins correctly. If the module is connected properly, it prints 'Radio initialized successfully.'.

❓ Predict Output

intermediate

What will be the output when sending data with nRF24L01?

Given the following Arduino code snippet that attempts to send a message using nRF24L01, what will be printed on the Serial Monitor?

Arduino

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10);
const byte address[6] = "00001";

void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.openWritingPipe(address);
  radio.stopListening();
  const char text[] = "Hello";
  bool report = radio.write(text, sizeof(text));
  if (report) {
    Serial.println("Data sent successfully.");
  } else {
    Serial.println("Data send failed.");
  }
}

void loop() {}

A No output because Serial.begin is missing.

B Data send failed.

C Compilation error due to wrong write argument.

D Data sent successfully.

💡 Hint

The radio.write() returns true if data is sent successfully.

The code sets the radio to write mode and sends the 'Hello' string. If the transmission succeeds, it prints 'Data sent successfully.'.

🔧 Debug

advanced

Why does this nRF24L01 receiver code never print received data?

Examine the following Arduino receiver code using nRF24L01. It never prints any received data. What is the most likely cause?

Arduino

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10);
const byte address[6] = "00001";

void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.openReadingPipe(1, address);
  radio.startListening();
}

void loop() {
  if (radio.available()) {
    char text[32] = {0};
    radio.read(text, sizeof(text));
    Serial.print("Received: ");
    Serial.println(text);
  }
}

A The radio.startListening() is missing, so it never listens.

B The address used for reading pipe does not match the sender's writing pipe address.

C The radio.read() function is called with wrong argument type causing runtime error.

D The Serial.begin() baud rate is too low to print data.

💡 Hint

The receiver must listen on the same address the sender writes to.

If the receiver's reading pipe address does not match the sender's writing pipe address, no data will be received, so radio.available() remains false.

📝 Syntax

advanced

Which option causes a compilation error in this nRF24L01 code snippet?

Look at these four code snippets initializing the nRF24L01 radio. Which one will cause a compilation error?

A RF24 radio(9, 10); // CE=9, CSN=10

B RF24 radio(9, 10, 11); // Three pins provided

C RF24 radio(9); // Only one pin provided

D RF24 radio(9, 10); radio.begin();

💡 Hint

Check the RF24 constructor parameters in the library documentation.

The RF24 constructor requires exactly two pins: CE and CSN. Providing only one pin causes a compilation error due to missing argument.

🚀 Application

expert

How many bytes are transmitted when sending this data with nRF24L01?

Consider this Arduino code sending an integer array via nRF24L01. How many bytes are actually sent over the air?

Arduino

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10);
const byte address[6] = "00001";

void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.openWritingPipe(address);
  radio.stopListening();
  int data[3] = {100, 200, 300};
  radio.write(&data, sizeof(data));
  Serial.print("Bytes sent: ");
  Serial.println(sizeof(data));
}

void loop() {}

A 6 bytes

B 12 bytes

C 3 bytes

D Depends on the radio payload size setting

💡 Hint

An int in Arduino Uno is 2 bytes. Multiply by array length.

On Arduino Uno, 'int' is 2 bytes (16-bit AVR). The array has 3 elements, so sizeof(data) = 6 bytes, which are transmitted by radio.write(&data, sizeof(data)).