NRF24L01+

Dedicated tutorial to install this library for a Raspberry.
The main goal of this tutorial is prepare a new environment to install and use the dedicated library to use properly the NRF24L01+ with Python 2 and Python 3

Documentation about classes:

• RF24 - Official library documentation

Prepare the system

• Create a dedicated user
• Enable SPI pins (depending on the Raspberry version)

sudo raspi-config

• Depending on the version, you should go into the "Advanced Options" or "Interfacing Options"
• Enable the SPI kernel module
• Reboot your system

sudo reboot

• Add your new user into the GPIO group

usermod -aG gpio user_name

• Add your new user into the SPI group

usermod -aG spi user_name

• To continue these installation steps, please install these packages

apt-get install python-pip python-dev python3-dev build-essential libboost-python-dev python-setuptools

• Create a symlink with the python 3 libboost (the real file name depends on your python 3 version)

ln -s /usr/lib/arm-linux-gnueabihf/libboost_python-py35.so /usr/lib/arm-linux-gnueabihf/libboost_python3.so

Installation into Python virtualenv

Virtualenv requirements

You have to be into your home directory to execute these commands.
For this installation, we use Python 3.

• Install virtualenv python library

pip install virtualenv virtualenvwrapper

• Make a backup of your bashrc

cp .bashrc .bashrc.bk

• This command will create a directory to save every virtualenv

printf '\n%s\n%s\n%s' '# virtualenv' 'export WORKON_HOME=~/virtualenvs' 'source /usr/local/bin/virtualenvwrapper.sh' >> ~/.bashrc

• Reload the .bashrc

source .bashrc

• Create the directory (if not exist)

mkdir -p $WORKON_HOME

• Create a virtualenv using python 3 (replace the project with your project name)

mkvirtualenv -p $(which python3) project

Clone the project

• Then clone the project into the workspace directory

git clone repository_url

Installation of python requirements

For these commands, you should be into the cloned project directory.
If these commands doesn't work, you can try with the sudo but be careful, you have to use your virtualenv and not the Python included into your system.
If you have to do this in sudo, replace the python work with the location of your python into your virtualenv.

• Example:

python3 setup.py install

• will become

sudo location/to/my/virtualenv/bin/python3 setup.py install

So continue this tutorial installation:

• Install python requirements

pip install -r requirements.txt

Installation of the python library (for the NRF24L01+)

• Go into the pyRF24 directory

cd pyRF24

• Build the library (into your virtualenv)

python3 setup.py build

• Then install the library (into your virtualenv)

python3 setup.py install

Use the NRF24 library with Python

• Finally, create your python file and execute it

python3 my_file.py

If you have some issue with the error message "Segmentation fault", it's because you have to use your python in sudo mode.
I had the same issue, even when I added the access rights to GPIO and SPI.
I currently doesn't have any idea why this issue happens.
So, just like explained before: execute this command to run your python file in sudo mode:

sudo location/to/my/virtualenv/bin/python3 my_file.py

Example

Raspberry configuration

PIN

NRF24L01+ Pin name (Pin number) => Raspberry Pin number (GPIO)
GND (1) => 6 (Ground; any GND pin)
VCC (2) => 1 (3.3v; any 3.3v pin)
CE (3) => 15 (GPIO22)
CSN (4) => 24 (GPIO08; SPI_CE0_N)
SCLK (5) => 23 (GPIO11; SPI_CLK)
MOSI (6) => 19 (GPIO10; SPI_MOSI)
MISO (7) => 21 (GPIO09; SPI_MISO)
IRQ (8) => 18 (GPIO24) Optional

Code (python)

#!/usr/bin/env python
# Homiot Copyright 2018
# Private software - No copy/reproduction without explicit authorization
#
import time
from RF24 import *
import RPi.GPIO as GPIO

irq_gpio_pin = None
# RF24(CE Pin, CSN Pin, SPI Speed)
# Setup for GPIO 22 CE and CE0 CSN with SPI Speed @ 16Mhz
# Pin CE = 15; CSN = 0 (it's not a pin, it's the SPI interface to use, between 0 and 1)
radio = RF24(RPI_V2_GPIO_P1_15, BCM2835_SPI_CS0, BCM2835_SPI_SPEED_16MHZ)
# Alternative configuration, depending on the Raspberry version (not tested)
#RPi B
# Setup for GPIO 15 CE and CE1 CSN with SPI Speed @ 8Mhz
#radio = RF24(RPI_V2_GPIO_P1_15, BCM2835_SPI_CS0, BCM2835_SPI_SPEED_8MHZ)
#RPi B+
# Setup for GPIO 22 CE and CE0 CSN for RPi B+ with SPI Speed @ 8Mhz
#radio = RF24(RPI_BPLUS_GPIO_J8_15, RPI_BPLUS_GPIO_J8_24, BCM2835_SPI_SPEED_8MHZ)
# Setup for connected IRQ pin, GPIO 24 on RPi B+;
# If you plug the IRQ pin, you can uncomment this line
#irq_gpio_pin = RPI_BPLUS_GPIO_J8_18


##########################################
def read_something(number_pin_event=False):
    if radio.available():
        while radio.available():
            size = radio.getDynamicPayloadSize()
            raw_data = radio.read(size)
            message = raw_data.decode('utf-8')
            print('Got payload size={} value="{}"'.format(size, message))
            # First, stop listening so we can talk
            radio.stopListening()
            # Encode it (str to byte)
            write_something(str.encode(message))

def write_something(message):
    radio.stopListening()
    v = radio.write(message)
    if v:
        print("Write success")
    else:
        prin("Write fail")
    radio.startListening()

pipe_read = 0xF0F0F0F0E1
pipe_write = 0xE8E8F0F0E1
channel = 0x76
radio.begin()
radio.enableDynamicPayloads()
radio.enableAckPayload()
#radio.setRetries(0,0)
radio.setPALevel(RF24_PA_MIN)
radio.setAutoAck(True)
radio.setChannel(channel)
radio.printDetails()

if irq_gpio_pin:
    # set up callback for irq pin
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(irq_gpio_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    GPIO.add_event_detect(irq_gpio_pin, GPIO.FALLING, callback=read_something)

radio.openWritingPipe(pipe_write)
radio.openReadingPipe(1, pipe_read)
radio.startListening()
# Send a first message
write_something(b"Coucou - Hello - Haha")
# forever loop
cpt = 0
while 1:
    # if there is data ready
    if not irq_gpio_pin:
        # no irq pin is set up -> poll it
        read_something()
    else:
        # callback routine set for irq pin takes care for reading -
        # do nothing, just sleeps in order not to burn cpu by looping
        time.sleep(0.11)
    cpt += 1
    if cpt > 100:
        cpt = 0
        write_something(b"Je n'ai pas eu ton message =/")

Arduino configuration

PIN

NRF24L01+ Pin name (Pin number) => Arduino Pin number
GND (1) => Any GND pin
VCC (2) => Any 3.3v pin
CE (3) => 7
CSN (4) => 8
SCLK (5) => 52
MOSI (6) => 51
MISO (7) => 50
IRQ (8) => Not used

Code (C)

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

RF24 radio(7, 8); // CE, CSN
void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.setPALevel(RF24_PA_MIN);
  radio.setDataRate(RF24_250KBPS);
  radio.setChannel(0x76);
  radio.openWritingPipe(0xF0F0F0F0E1LL);
  radio.openReadingPipe(1, 0xE8E8F0F0E1LL);
  radio.enableDynamicPayloads();
}

void loop() {
  boolean sent = false;
  int cpt = 0;
  int retry = 10;
  radio.startListening();
  char receivedMessage[32];
  if(radio.available()){
      Serial.println("Radio available to receive something");
      int size = radio.getDynamicPayloadSize();
      radio.read(receivedMessage, size);
      Serial.println(receivedMessage);
      radio.stopListening();
      Serial.println("Re-send the message");
      while (cpt < retry && !radio.write(&receivedMessage, sizeof(receivedMessage))) {
        cpt++;
      }
      if(cpt <= retry){
        sent = true;
      }
      if(sent){
        Serial.println("Re-Send SUCCESS");
      }
      else {
        Serial.println("Re-Send FAIL!");
      }
      delay(100);
  }
  delay(110);
}

Note: if you have issue about packet lost during message sending, you can try to put a 10µf (10V) on the NRF24L01+ module, from the GND and the 3.3v

See http://tmrh20.github.io/RF24 for all documentation