Noob Question - Sending Data With NRF24L01

Forum 2005-2010 (read only) Hardware Interfacing
1

Since this is my first time posting, this message is so that I can put a link in my question.

2

Hello all, I've just started working with Arduino, having almost zero prior electronics or coding experience. My background is mostly a course I took coding in C++.

The project I'm currently working on is to have one Arduino read a potentiometer and send the data via an NRF24L01 module (SparkFun Transceiver Breakout - nRF24L01+ - WRL-00691 - SparkFun Electronics) to another Arduino with the same module. Right now, I have them both interfaced with USB, and I'm trying to get serial printouts of the data being sent.

I read this page: Arduino Playground - Nrf24L01 and started by modifying the examples that came with the mirf library. The sending Arduino is running the following:

#include <Spi.h>
#include <mirf.h>
#include <nRF24L01.h>

void setup(){
  Serial.begin(9600); 
  Mirf.init();
  Mirf.setRADDR((byte *)"clie1");
  Mirf.config();
  Mirf.payload = sizeof(int);
}

void loop(){
  //byte data[Mirf.payload];
  Mirf.setTADDR((byte *)"serv1");
  
  Mirf.send((byte *)"hello");
  
  while(Mirf.isSending()){
  }
  Serial.println("Finished sending");
  delay(10);
}

and the receiving Arduino is running:

#include <Spi.h>
#include <mirf.h>
#include <nRF24L01.h>

void setup(){
  Serial.begin(9600); 
  Mirf.init(); 
  Mirf.setRADDR((byte *)"serv1");
  Mirf.config();
  Mirf.payload = sizeof(int);
}

void loop(){
  byte data[Mirf.payload];

  if(Mirf.dataReady()){
    
    do{
      Serial.println("Got packet");
     
      Mirf.getData(data);
      
      Serial.println(data[0]);
      
    }while(!Mirf.rxFifoEmpty());
  }
}

Now as long as I'm sending a string, such as "hello", I can print out the received array one letter at a time (or more, if I use a for loop). However, if I send a number, the printed result doesn't seem to correspond at all. That is, if the sending syntax is:

Mirf.send((byte *)1024);

What am I doing wrong/missing? Do I need to format the sent data as an array, which is why sending a string works? Please help me out!

Thanks.

3

Is it possible you're sending an ascii number, and the result on the receiving side is the decimal equivalent of the number you sent? Ascii chart located http://www.asciitable.com/

4

I thought about that, but no, the numbers seem completely unrelated, and most of them are out of the range of the ascii chart.

5

Hi

I think the code you've got there will try and send sizeof(int) bytes located at memory address 1024. You need to create a variable with your number in first:

int temp = 1024;
Mirf.send((byte *) &temp);
6

Mirf.send((byte *)1024);

What is the data at address 1024?

7

Hello again, thanks for the responses. 1024 is just an arbitrary number that I tried sending.

I tried aaronds suggestions of creating a variable to hold the number (something I had done before), but on the receiving end it prints a blank line. If I cast the received data as an integer, the output still seems arbitrary.

Serial.println((int)data[0]);

When using 1024, the output for data[0] is 0, the output for data[1] is 4, data[2] is 194 and data[3] is 0 again. I thought the array would only be that long, but data[4] is 0 and data[5] is 15. I haven't felt like checking beyond that.

8

Try something like this on the server:

int data;

Mirf.getData((byte *) &data);
Serial.println(data);

I think it actually working it's just not being printed out right.

9

Holy Crap. I don't fully understand it, but it works! Thanks so much!

10

Hello again, thanks for the responses. 1024 is just an arbitrary number that I tried sending

No, it isn't arbitrary, it is the address of some data that the routine expects - you even cast it to be a byte pointer.