Can't receive data from Arduino to Raspberry via nrf24l01+

Question

Please help me to solve the problem. I do not get data at Raspberry.
I have:
1. Arduino Nano + DHT11 + NRF24l01+
2. Raspberry Pi 3 + NRF24l01+
Raspberry RF24 library https://github.com/stanleyseow/RF24.git
Arduino code:

#include "DHT.h"
#include <SPI.h>
#include "RF24.h"
#define DHTPIN 2     // what digital pin we're connected to
#define DHTTYPE DHT11   // DHT 11

RF24 radio(7,8);

unsigned long count = 0;
int sensor1 = 2;

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();
  radio.begin();
  radio.setPALevel(RF24_PA_MAX);
  radio.setChannel(0x4c);
  radio.openWritingPipe(0xF0F0F0F0E1LL);
  radio.enableDynamicPayloads();
  radio.powerUp();
  pinMode(sensor1, INPUT);
  pinMode(3, OUTPUT);
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  float hic = dht.computeHeatIndex(t, h, false);
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.println(" *C ");

    char outBuffer[32]= "";

    char buffer[10];
    String temp = dtostrf(t,3,1,buffer);
    String hum = dtostrf(h,3,1,buffer);
    String out = temp + "; " + hum + ";"; 
    out.toCharArray(outBuffer, 32);
    radio.write(outBuffer, 32);
}

Raspberry code:

    #include <cstdlib>
#include <iostream>
#include "/home/pi/RF24/RPi/RF24/RF24.h"
#include <fstream>
using namespace std;

// spi device, spi speed, ce gpio pin
//RF24 radio("/dev/spidev0.0",8000000,25);
RF24 radio(RPI_V2_GPIO_P1_22, RPI_V2_GPIO_P1_24, BCM2835_SPI_SPEED_8MHZ);

void setup(void)
{
    // init radio for reading
    radio.begin();
    radio.enableDynamicPayloads();
    radio.setAutoAck(1);
    radio.setRetries(15,15);
    radio.setDataRate(RF24_1MBPS);
    radio.setPALevel(RF24_PA_MAX);
    radio.setChannel(76);
    radio.setCRCLength(RF24_CRC_16);
    radio.openReadingPipe(1,0xF0F0F0F0E1LL);
    radio.startListening();
}

void loop(void)
{
char receivePayload[64];
    while (radio.available())
    {
uint8_t len = radio.getDynamicPayloadSize();
radio.read(receivePayload, len);
// Костыль для создания промежуточного файла.
//ofstream out("/dev/nrf24");
//out << receivePayload << "\n";
//out.close ();
cout<<"\n Data="<<receivePayload;
delay(200);
    }
}

int main(int argc, char** argv)
{
cout << "Driver initialized, please check values of /dev/nrf24" << endl;
    setup();
    while(1)
        loop();

    return 0;
}

Raspberry schema:

What is wrong? Thank you.

Answer 1

I found it rather confusing that the nRF24 library (at least the Arduino one from TMRh20) already configuers the module in the constructor. I could not find any documentation about it but found it in the source code and by using a logic analyzer. So it was very annoying as the configuration deviates form the devices default values. I can imagine that the RPi library does different initialization steps leading into incompatibility in communication.

I also noticed you've set the transmission level to RF24_PA_MAX. Try reducing it to RF24_PA_MIN. The modules can't read the signal if it is too strong as @Greben stated.

Answer 2

I also faced the same problem.

What I found is the data send by Arduino has difference in trigger clock when it reaches raspberry Pi. As a result we get garbage values.

To overcome this problem we can use an Arduino connected to the Pi through a USB cable and an nrf24l01 connected to the Arduino. Then use the master-slave procedure to get the receiver end reading on Pi.

For more details on this method, see https://robofever.in/

Answer 3

Try adding delay(20) before the final bracket in the RPi loop function.

Answer 4

Refer to this tutorial:

http://invent.module143.com/daskal_tutorial/rpi-3-tutorial-14-wireless-pi-to-arduino-communication-with-nrf24l01/

Follow instructions exactly, it should work.

Answer 5

The Suggestion by QGLV worked for me. It looks like we need to introduce a delay between successive calls of RF24::available() on the Pi. the 20 millisecond delay suggested by QGLV worked for the most part for me (I used usleep(20000) for the delay), although I still saw rare instances of corrupted payloads. Increasing the delay did not seem to help, as I still saw a few corrupted payloads with 100ms delay. I'm using a Pi Zero, so your mileage may vary.