Problem with NRF24L01 transmitting Strings

Projects Programming
1

Hi everyone,
I'm having an issue with transmitting (or receiving, I'm not sure exactly where the problem is occurring) Strings between two NRF24L01 modules. I have one set up as a transmitter and one as a receiver. The codes are below, one simply spits out a String and the other listens for it. The codes work just fine if I use an int or a simple char, but when I try to use a String to send text, I get some gibberish and then a failure. I haven't the slightest clue what's going on, I haven't been doing Arduino for that long.
Here's the code for the transmitter;

#include <SPI.h>
#include "RF24.h"
bool radioNumber = 0;
RF24 radio(7,8);
byte addresses[][6] = {"1Node","2Node"};

void setup() {
  Serial.begin(115200);
  Serial.println(F("Starting- Transmitter"));
  radio.begin();

  if(radioNumber){
    radio.openWritingPipe(addresses[1]);
    radio.openReadingPipe(1,addresses[0]);
  }else{
    radio.openWritingPipe(addresses[0]);
    radio.openReadingPipe(1,addresses[1]);
  }
}

void loop() {  
    Serial.println(F("Now sending"));

     String test = "Test";
   
     if (!radio.write( &test, sizeof(String) )){
       Serial.println(F("failed"));
     }
 
        Serial.print(F("Sent "));
        Serial.println(test);
      
    delay(2000);
}

Here's the code for the receiver;

#include <SPI.h>
#include "RF24.h"
bool radioNumber = 1;
RF24 radio(7,8);
byte addresses[][6] = {"1Node","2Node"};

void setup() {
  Serial.begin(115200);
  Serial.println(F("Starting- Receiver"));
  radio.begin();

  if(radioNumber){
    radio.openWritingPipe(addresses[1]);
    radio.openReadingPipe(1,addresses[0]);
  }else{
    radio.openWritingPipe(addresses[0]);
    radio.openReadingPipe(1,addresses[1]);
  }
  radio.startListening();
}

void loop() {
    String test;
    
    if( radio.available()){
                                                                    // Variable for the received timestamp
      while (radio.available()) {                                   // While there is data ready
        radio.read( &test, sizeof(String) );             // Get the payload
      }
    
      Serial.print("Got: ");
      Serial.println(test);  
   }
 }

This is what the Serial monitor gives on the transmitter side;

Starting- Transmitter
Now sending
Sent Test
Now sending
Sent Test
Now sending
Sent Test
Now sending
Sent Test
Now sending
Sent Test
Now sending
failed
Sent Test
Now sending
failed
Sent Test
Now sending
failed
Sent Test
Now sending
failed
Sent Test
Now sending
failed
Sent Test

It just goes on like this.

And here's the Serial monitor on the receiver side;

Starting- Receiver
Got: ö/*
Got: /*

Like I said, I have no idea what this means. Any help would be greatly appreciated.
Thanks
~Josh Blackburn

2

I suggest you use the TMRh20 version of the RF24 library - it solves some problems from the ManiacBug version

The RF24 library sends an array of bytes.

It is not a good idea to use Strings (capital S) in the small memory of an Arduino. If you use strings (small s - a char array terminated with 0) it will be compatible with the RF24 library. For example

char test[]  = "Test";

You also have a mistake in this line

if (!radio.write( &test, sizeof(String) )){

it should be

if (!radio.write( &test, sizeof(test) )){

You may need to make corresponding changes in the receiver code
...R