nRF24L01 Problem

Question

I'm trying to code a simple transmitter - Receiver program with nRF24L01

Very simple code. Compiles. But when I try to test it using serial monitor. But only the first character is printed on the screen just once.

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

#define CE_PIN 9
#define CSN_PIN 10


const uint64_t pipe = 0xE8E8F0F0E1LL;

RF24 radio(CE_PIN, CSN_PIN);

int smth[1];  // the transmitter data
int x=0;  // the copy of the receiver data
char rec[1]; //the receiver data

int ledPin = 3; // choose the pin for the LED
int inPin = 7;   // choose the input pin (for a pushbutton)
int val = 0;     // variable for reading the pin status


void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);  // declare LED as output
  pinMode(inPin, INPUT);    // declare pushbutton as input

  radio.begin();
  radio.openWritingPipe(pipe);  //originally transmitter
}

void loop(){
  val = digitalRead(inPin);  // read input value
  if (val==HIGH) {         // check if the input is HIGH (button released)
    digitalWrite(ledPin, HIGH);  // turn LED OFF
    Serial.println('1');
    smth[0] = '1';
    radio.write(smth, sizeof(smth));
  } else {
    digitalWrite(ledPin, LOW);  // turn LED ON
    Serial.println('0');
    smth[0] = '0';
    radio.write(smth, sizeof(smth));
  }
}

---

Serial Monitor :

0

---

Instead of printing a zeros for infinite time till I change the mode of the switch, even though if I change the mode of the switch from low to high, nothing is printed on the screen.

I'm using Library for instance http://playground.arduino.cc/InterfacingWithHardware/Nrf24L01

Any help?

Answer 1

A quick look at the library header files shows you should call radio.stopListening() before calling radio.write() for the module to switch to transmit mode. This could be what is blocking the radio.write in the else block. I also recommend you try a byte array first, to get things working, just in case ints are the issue.

Answer 2

Completing TisteAndii reply I suggest to have a look at init. According to the RF24 classe list, it seems radio.begin(); and radio.openWritingPipe(pipe); are "void" function. I personnaly use NRFLite from Dave Parson and his lib send a return value for his _radio.init function. That's interesting because a lot of lib have a "send feature" which don't return until the receiver replied. So if you turn on your nRF and send data while the receiver is OFF, you're blocked. With a test at init, you can check that and loop until the receiver is available.

Note: I let my answer, but that's not the good one. As indicate in the coment, the init function dont tell if the receiver is avaible, but only if the nRF is connected (your nRF, so not the other one).