Если у вас есть проблема одновременного открытия двух окон SerialMonitor, в которые выводится информация от двух Arduino, подключенных к разным портам, нужно сначала запустить ArduinoStuio в обычном режиме и отобразить информацию с одного порта, а потом запустить среду ArduinoStuio в режиме "от администратора"  и отобразить информацию с другого порта.

/*
 * See documentation at https://nRF24.github.io/RF24
 * See License information at root directory of this library
 * Author: Brendan Doherty (2bndy5)
 */

/**
 * A simple example of sending data from 1 nRF24L01 transceiver to another.
 *
 * This example was written to be used on 2 devices acting as "nodes".
 * Use the Serial Monitor to change each node's behavior.
 */
#include <SPI.h>
#include "printf.h"
#include "RF24.h"

// instantiate an object for the nRF24L01 transceiver
RF24 radio(7, 8); // using pin 7 for the CE pin, and pin 8 for the CSN pin

// Let these addresses be used for the pair
uint8_t address[][6] = {"1Node", "2Node"};
// It is very helpful to think of an address as a path instead of as
// an identifying device destination

// to use different addresses on a pair of radios, we need a variable to
// uniquely identify which address this radio will use to transmit
bool radioNumber = 1; // 0 uses address[0] to transmit, 1 uses address[1] to transmit

// Used to control whether this node is sending or receiving
bool role = false;  // true = TX role, false = RX role

// For this example, we'll be using a payload containing
// a single float number that will be incremented
// on every successful transmission
float payload = 0.0;

void setup() {

  Serial.begin(115200);
  while (!Serial) {
    // some boards need to wait to ensure access to serial over USB
  }

  // initialize the transceiver on the SPI bus
  if (!radio.begin()) {
    Serial.println(F("radio hardware is not responding!!"));
    while (1) {} // hold in infinite loop
  }

  // print example's introductory prompt
  Serial.println(F("RF24/examples/GettingStarted"));

  // To set the radioNumber via the Serial monitor on startup
  Serial.println(F("Which radio is this? Enter '0' or '1'. Defaults to '0'"));
  while (!Serial.available()) {
    // wait for user input
  }
  char input = Serial.parseInt();
  radioNumber = input == 1;
  Serial.print(F("radioNumber = "));
  Serial.println((int)radioNumber);

  // role variable is hardcoded to RX behavior, inform the user of this
  Serial.println(F("*** PRESS 'T' to begin transmitting to the other node"));

  // Set the PA Level low to try preventing power supply related problems
  // because these examples are likely run with nodes in close proximity to
  // each other.
  radio.setPALevel(RF24_PA_LOW);  // RF24_PA_MAX is default.

  // save on transmission time by setting the radio to only transmit the
  // number of bytes we need to transmit a float
  radio.setPayloadSize(sizeof(payload)); // float datatype occupies 4 bytes

  // set the TX address of the RX node into the TX pipe
  radio.openWritingPipe(address[radioNumber]);     // always uses pipe 0

  // set the RX address of the TX node into a RX pipe
  radio.openReadingPipe(1, address[!radioNumber]); // using pipe 1

  // additional setup specific to the node's role
  if (role) {
    radio.stopListening();  // put radio in TX mode
  } else {
    radio.startListening(); // put radio in RX mode
  }

  // For debugging info
  // printf_begin();             // needed only once for printing details
  // radio.printDetails();       // (smaller) function that prints raw register values
  // radio.printPrettyDetails(); // (larger) function that prints human readable data

} // setup

void loop() {

  if (role) {
    // This device is a TX node

    unsigned long start_timer = micros();                    // start the timer
    bool report = radio.write(&payload, sizeof(float));      // transmit & save the report
    unsigned long end_timer = micros();                      // end the timer

    if (report) {
      Serial.print(F("Transmission successful! "));          // payload was delivered
      Serial.print(F("Time to transmit = "));
      Serial.print(end_timer - start_timer);                 // print the timer result
      Serial.print(F(" us. Sent: "));
      Serial.println(payload);                               // print payload sent
      payload += 0.01;                                       // increment float payload
    } else {
      Serial.println(F("Transmission failed or timed out")); // payload was not delivered
    }

    // to make this example readable in the serial monitor
    delay(1000);  // slow transmissions down by 1 second

  } else {
    // This device is a RX node

    uint8_t pipe;
    if (radio.available(&pipe)) {             // is there a payload? get the pipe number that recieved it
      uint8_t bytes = radio.getPayloadSize(); // get the size of the payload
      radio.read(&payload, bytes);            // fetch payload from FIFO
      Serial.print(F("Received "));
      Serial.print(bytes);                    // print the size of the payload
      Serial.print(F(" bytes on pipe "));
      Serial.print(pipe);                     // print the pipe number
      Serial.print(F(": "));
      Serial.println(payload);                // print the payload's value
    }
  } // role

  if (Serial.available()) {
    // change the role via the serial monitor

    char c = toupper(Serial.read());
    if (c == 'T' && !role) {
      // Become the TX node

      role = true;
      Serial.println(F("*** CHANGING TO TRANSMIT ROLE -- PRESS 'R' TO SWITCH BACK"));
      radio.stopListening();

    } else if (c == 'R' && role) {
      // Become the RX node

      role = false;
      Serial.println(F("*** CHANGING TO RECEIVE ROLE -- PRESS 'T' TO SWITCH BACK"));
      radio.startListening();
    }
  }

} // loop

Изначально, моя Raspberry Pi поставлялась в комплекте с дисплеем, подключаемым к тем же портам, что и NRFL01 модуль. После того, как дисплей убран, нужно отредактировать файл boot/config.txt , закоментировав строки, относящиеся к дисплею. В моем случае незакоментированной осталась только строка

dtparam=spi=on

1. Install prerequisites if there are any (MRAA, LittleWire libraries, setup SPI device etc)

2. Download the install.sh file from http://tmrh20.github.io/RF24Installer/RPi/install.sh

   wget http://tmrh20.github.io/RF24Installer/RPi/install.sh

3. Make it executable

   chmod +x install.sh

4. Run it and choose your options

   ./install.sh

5. Run an example from one of the libraries

   cd rf24libs/RF24/examples_linux

   Edit the gettingstarted example, to set your pin configuration

   nano gettingstarted.cpp
   make
   sudo ./gettingstarted

"""
A simple example of sending data from 1 nRF24L01 transceiver to another.
This example was written to be used on 2 devices acting as 'nodes'.
"""
import sys
import argparse
import time
import struct
from RF24 import RF24, RF24_PA_LOW


parser = argparse.ArgumentParser(
    description=doc,
    formatter_class=argparse.RawDescriptionHelpFormatter
)
parser.add_argument(
    "-n",
    "--node",
    type=int,
    choices=range(2),
    help="the identifying radio number (or node ID number)"
)
parser.add_argument(
    "-r",
    "--role",
    type=int,
    choices=range(2),
    help="'1' specifies the TX role. '0' specifies the RX role."
)
########### USER CONFIGURATION ###########
See https://github.com/TMRh20/RF24/blob/master/pyRF24/readme.md
Radio CE Pin, CSN Pin, SPI Speed
CE Pin uses GPIO number with BCM and SPIDEV drivers, other platforms use
their own pin numbering
CS Pin addresses the SPI bus number at /dev/spidev<a>.<b>
ie: RF24 radio(<ce_pin>, <a>*10+<b>); spidev1.0 is 10, spidev1.1 is 11 etc..
Generic:
radio = RF24(22, 0)
################## Linux (BBB,x86,etc) #########################
See http://nRF24.github.io/RF24/pages.html for more information on usage
See http://iotdk.intel.com/docs/master/mraa/ for more information on MRAA
See https://www.kernel.org/doc/Documentation/spi/spidev for more
information on SPIDEV
using the python keyword global is bad practice. Instead we'll use a 1 item
list to store our float number for the payloads sent/received
payload = [0.0]
def master():
    """Transmits an incrementing float every second"""
    radio.stopListening()  # put radio in TX mode
    failures = 0
    while failures < 6:
        # use struct.pack() to packet your data into the payload
        # "<f" means a single little endian (4 byte) float value.
        buffer = struct.pack("<f", payload[0])
        start_timer = time.monotonic_ns()  # start timer
        result = radio.write(buffer)
        end_timer = time.monotonic_ns()  # end timer
        if not result:
            print("Transmission failed or timed out")
            failures += 1
        else:
            print(
                "Transmission successful! Time to Transmit: "
                "{} us. Sent: {}".format(
                    (end_timer - start_timer) / 1000,
                    payload[0]
                )
            )
            payload[0] += 0.01
        time.sleep(1)
    print(failures, "failures detected. Leaving TX role.")
def slave(timeout=6):
    """Listen for any payloads and print the transaction
:param int timeout: The number of seconds to wait (with no transmission)
    until exiting function.
"""
radio.startListening()  # put radio in RX mode

start_timer = time.monotonic()
while (time.monotonic() - start_timer) &lt; timeout:
    has_payload, pipe_number = radio.available_pipe()
    if has_payload:
        # fetch 1 payload from RX FIFO
        buffer = radio.read(radio.payloadSize)
        # use struct.unpack() to convert the buffer into usable data
        # expecting a little endian float, thus the format string "&lt;f"
        # buffer[:4] truncates padded 0s in case payloadSize was not set
        payload[0] = struct.unpack("&lt;f", buffer[:4])[0]
        # print details about the received packet
        print(
            "Received {} bytes on pipe {}: {}".format(
                radio.payloadSize,
                pipe_number,
                payload[0]
            )
        )
        start_timer = time.monotonic()  # reset the timeout timer

print("Nothing received in", timeout, "seconds. Leaving RX role")
# recommended behavior is to keep in TX mode while idle
radio.stopListening()  # put the radio in TX mode

def set_role():
    """Set the role using stdin stream. Timeout arg for slave() can be
    specified using a space delimiter (e.g. 'R 10' calls slave(10))
:return:
    - True when role is complete &amp; app should continue running.
    - False when app should exit
"""
user_input = input(
    "*** Enter 'R' for receiver role.\n"
    "*** Enter 'T' for transmitter role.\n"
    "*** Enter 'Q' to quit example.\n"
) or "?"
user_input = user_input.split()
if user_input[0].upper().startswith("R"):
    if len(user_input) &gt; 1:
        slave(int(user_input[1]))
    else:
        slave()
    return True
elif user_input[0].upper().startswith("T"):
    master()
    return True
elif user_input[0].upper().startswith("Q"):
    radio.powerDown()
    return False
print(user_input[0], "is an unrecognized input. Please try again.")
return set_role()

if name == "main":
args = parser.parse_args()  # parse any CLI args

# initialize the nRF24L01 on the spi bus
if not radio.begin():
    raise RuntimeError("radio hardware is not responding")

# For this example, we will use different addresses
# An address need to be a buffer protocol object (bytearray)
address = [b"1Node", b"2Node"]
# It is very helpful to think of an address as a path instead of as
# an identifying device destination

print(sys.argv[0])  # print example name

# to use different addresses on a pair of radios, we need a variable to
# uniquely identify which address this radio will use to transmit
# 0 uses address[0] to transmit, 1 uses address[1] to transmit
radio_number = args.node  # uses default value from `parser`
if args.node is None:  # if '--node' arg wasn't specified
    radio_number = bool(
        int(
            input(
                "Which radio is this? Enter '0' or '1'. Defaults to '0' "
            ) or 0
        )
    )

# set the Power Amplifier level to -12 dBm since this test example is
# usually run with nRF24L01 transceivers in close proximity of each other
radio.setPALevel(RF24_PA_LOW)  # RF24_PA_MAX is default

# set the TX address of the RX node into the TX pipe
radio.openWritingPipe(address[radio_number])  # always uses pipe 0

# set the RX address of the TX node into a RX pipe
radio.openReadingPipe(1, address[not radio_number])  # using pipe 1

# To save time during transmission, we'll set the payload size to be only
# what we need. A float value occupies 4 bytes in memory using
# struct.pack(); "&lt;f" means a little endian unsigned float
radio.payloadSize = len(struct.pack("&lt;f", payload[0]))

# for debugging, we have 2 options that print a large block of details
# (smaller) function that prints raw register values
# radio.printDetails()
# (larger) function that prints human readable data
# radio.printPrettyDetails()

try:
    if args.role is None:  # if not specified with CLI arg '-r'
        while set_role():
            pass  # continue example until 'Q' is entered
    else:  # if role was set using CLI args
        # run role once and exit
        master() if bool(args.role) else slave()
except KeyboardInterrupt:
    print(" Keyboard Interrupt detected. Exiting...")
    radio.powerDown()
    sys.exit()

#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include <NewPing.h>
//static char send_payload[256];

#define TRIGGER_PIN 4      //Trig pin
#define ECHO_PIN  3        //Echo pin
#define MAX_DIST 400

const int min_payload_size = 4;
const int max_payload_size = 32;
const int payload_size_increments_by = 1;
int next_payload_size = min_payload_size;
float send_payload = 0.0;


NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DIST);
RF24 radio(7, 8); //
//const int role_pin = 5;

// Radio pipe addresses for the 2 nodes to communicate.
uint8_t address[][6] = {"1Node", "2Node"}; //
char receive_payload[max_payload_size + 1];
void setup()
{
  Serial.begin(115200);
  radio.begin();
  radio.enableDynamicPayloads();
  radio.setRetries(5, 15);
  radio.openWritingPipe(address[0]); //
  radio.openReadingPipe(1, address[1]); //
  radio.startListening();
}

void loop(void)
{
  int water_level = sonar.ping_cm();
  Serial.print("Sending Data :");
  Serial.print(water_level);
  Serial.println(" cm");
  //delay(1000);
  String water = String(water_level);
 
 radio.stopListening();
  send_payload = water_level;
  unsigned long start_timer = micros();                    // start the timer
  radio.write(&send_payload, sizeof(float)); 
  unsigned long end_timer = micros();                      // end the timer
  Serial.print(F("Time to transmit = "));
  Serial.print(end_timer - start_timer);                 // print the timer result
  Serial.print(F(" us. Sent: "));

}