Trying to use NRF24L01+ on ESP8266, using the ESP8266 as MCU (i.e. not an Arduino or ATmega328). See https://github.com/esp8266/Arduino for details on initial setup of ESP8266 as Arduino-compatible MCU. The serial output below does not show expected messages: a) the full output shows up all at once then stops dead and b) the values for _salt, vo…

ESP8266 Code (RX node)

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

#define DEVICE_ID 2
#define CHANNEL 1 //MAX 127
RF24 radio(15, 15);                // Set up nRF24L01 radio on SPI bus plus pins 7 & 8

// Topology
const uint64_t pipes[2] = { 0xFFFFFFFFFFLL, 0xCCCCCCCCCCLL };

struct dataStruct{
  unsigned long _salt;
  float temp;
  int volt;
}sensor_data;

void setup() {
  ESP.wdtDisable();
//  ESP.wdtFeed();
  Serial.begin(115200);
  Serial.println("starting......");
  restartRadio();                    // turn on and configure radio  
  Serial.println("restarting radio");
  radio.startListening();
  Serial.println("Listening for sensor values..."); 
}

void loop() {
  if (radio.available()) {
    while (radio.available()) {
      radio.read(&sensor_data, sizeof(sensor_data));
      Serial.println("Got message:");
      Serial.print("_salt: ");
      Serial.println(sensor_data._salt);
      Serial.print("volt: ");
      Serial.println(sensor_data.volt);
      Serial.print("temp: ");
      Serial.println(sensor_data.temp);
      Serial.println("-----------");
    }
  }
}

void restartRadio(){
  radio.begin(); // Start up the radio
  radio.setPALevel(RF24_PA_HIGH);
  radio.setDataRate(RF24_250KBPS);  
  //radio.openReadingPipe(1,pipes[1]);  
  //radio.openWritingPipe(pipes[0]);
  radio.openReadingPipe(1,pipes[0]);
  radio.openWritingPipe(pipes[1]);  
  radio.stopListening();
}

ESP8266 serial output (RX node)

rl��r��c�n������p�<����8��ǒ��p�nn��;�n�����b�$�rrp�n��܀����l���b�n��n�����p��nn�����l`���#�n�$��l`�`rn|��n����;`�n��n��Ì�<~�n���l`nn��܀�r����pp��<�����p��nn����l`���#�n�rnr���;��?�l�;p�n��܀�r��l��pp��<�����8��nn���r��#�n��;nr���;��?��8rr�ےn��r��`����(�SQS�(RQ�)HT�)SHHHC�dr�starting......
restarting radio
Listening for sensor values...
Got message:
_salt: 234884608
volt: 234881038
temp: 0.00
-----------
Got message:
_salt: 3584
volt: 921088
temp: 0.00
-----------
Got message:
_salt: 917504
volt: 235798542
temp: 0.00
-----------
Got message:
_salt: 235798542
volt: 917504
temp: 0.00
-----------
Got message:
_salt: 234884608
volt: 234884608
temp: 0.00
-----------
Got message:
_salt: 3584
volt: 234884608
temp: 0.00
-----------
Got message:
_salt: 0
volt: 234881038
temp: 0.00
-----------
Got message:
_salt: 917518
volt: 3584
temp: 0.00
-----------
Got message:
_salt: 234881024
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 14
temp: 0.00
-----------
Got message:
_salt: 28
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 3584
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 28
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 0
volt: 14
temp: 0.00
-----------
Got message:
_salt: 234881052
volt: 0
temp: 0.00
-----------
Got message:
_salt: 234884608
volt: 14
temp: 0.00
-----------
Got message:
_salt: 0
volt: 0
temp: 0.00
-----------
Got message:
_salt: 234881038
volt: 917518
temp: 0.00
-----------
Got message:
_salt: 917504
volt: 234884608
temp: 0.00
-----------
Got message:
_salt: 235802126
volt: 235

Temp Sensor with NRF24L01+ (TX node)

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include "LowPower.h"
#include "printf.h"

#define POWER 9                 //power pin to reduce consumption while sleeping

// TODO: store this in EEPROM
#define DEVICE_ID 1

#define CHANNEL 1 //MAX 127
RF24 radio(7, 8);               // Set up nRF24L01 radio on SPI bus plus pins 7 & 8
int tempVal = 0; // Variable to store the temp value coming from the sensor.
int voltVal = 0; // Variable to store the calculated current voltage value.

// Topology
// FIXME: can this be stored in EEPROM?
const uint64_t pipes[2] = { 0xFFFFFFFFFFLL, 0xCCCCCCCCCCLL };

// Adjust this value to your board's specific internal BG voltage
// This needs to be accurate to set per board to be able to report current battery voltage
// TODO: store this in EEPROM
const long InternalReferenceVoltage = 1078;

// Uncomment this line if you are using the updated dallas_temp_library that
// supports the busFail() method to diagnose bus problems
// #define BUSFAIL

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 6
#define TEMPERATURE_PRECISION 9
#define TEMP_SENSOR_ID 0

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);

struct dataStruct {
  unsigned long _salt;
  float temp;
  int volt;
} data;

void setup() {
  pinMode(POWER, OUTPUT);

  Serial.begin(115200);
  printf_begin();
  printf("Sending sensor values every 8 seconds...\n\r");
  restartRadio();
  radio.printDetails();
  data._salt = 0;
}

void loop() {
  // get all sensor values and increment the salt so we have at least one unique value in the payload
  data.volt = getBandgap();
  printf("Voltage: %d\r\n", data.volt);
  data.temp = getTemp(TEMP_SENSOR_ID);
  char tempTemp[10];
  dtostrf(data.temp, 4, 2, tempTemp);
  printf("Temperature: %s\r\n", tempTemp);
  data._salt++;
  printf("Salt: %d\r\n", data._salt);
  printf("------------------\r\n");

  // send sensor data to gateway
  restartRadio();                    // turn on and configure radio
  printf("Now sending %d byte payload... ", sizeof(data));
  if (!radio.write(&data , sizeof(data) )) { // Send via radio
    printf("failed.\n\r");
  } else {
    printf("sent.\n\r");
  }
  stopRadio();                       // stop the radio

  // Enter power down state for 8 s with ADC and BOD module disabled
  Serial.println("Sleeping...");
  Serial.flush();
  LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
  printf("waking up...\r\n");
}

/*
* Get temperature
*/
float getTemp(int tempSensorId) {
  #ifdef BUSFAIL
    testBus();
  #endif

//  int numberOfDevices; // Number of temperature devices found
  DeviceAddress tempDeviceAddress; // We'll use this variable to store a found device address
  float tempF;

  // Reset the bus every time so we can see if any devices appear or fall off
  sensors.begin();
  sensors.requestTemperatures(); // Send the command to get temperatures

  // Search the wire for address
  if (sensors.getAddress(tempDeviceAddress, tempSensorId)) {
    // get the temp in F
    tempF = DallasTemperature::toFahrenheit(sensors.getTempC(tempDeviceAddress));
  }

  return tempF;
}

// From: http://gammon.com.au/power
// Code courtesy of "Coding Badly" and "Retrolefty" from the Arduino forum
// results are Vcc * 100
// So for example, 5V would be 500.
int getBandgap () {
  // REFS0 : Selects AVcc external reference
  // MUX3 MUX2 MUX1 : Selects 1.1V (VBG)
  ADMUX = bit (REFS0) | bit (MUX3) | bit (MUX2) | bit (MUX1);
  ADCSRA |= bit( ADSC );  // start conversion
  while (ADCSRA & bit (ADSC))
  { }  // wait for conversion to complete
  int results = (((InternalReferenceVoltage * 1024) / ADC) + 5) / 10;
  return results;
}

void stopRadio() {

  radio.powerDown();

  digitalWrite(13, LOW);
  digitalWrite(12, LOW);
  digitalWrite(11, LOW);
  digitalWrite(7, LOW);
  digitalWrite(8, LOW);

  digitalWrite(POWER, LOW);  // remove power from nrf24l01+ module
}

void restartRadio() {
  digitalWrite(POWER, HIGH);         // provide power to nrf24l01+ module

  radio.begin(); // Start up the radio
  radio.setPALevel(RF24_PA_HIGH);
  radio.setDataRate(RF24_250KBPS);
  radio.openReadingPipe(1, pipes[1]);
  radio.openWritingPipe(pipes[0]);
  //  radio.openReadingPipe(1,pipes[0]);
  //  radio.openWritingPipe(pipes[1]);
  radio.stopListening();
}

/********
* This tests the Dallas One-Wire bus
* Only works with the updated dallas_temp_library that supports the
* budFail() method to diagnose bus problems
********/
void testBus() {
  #ifdef BUSFAIL
    Serial.print(" Test:");
    if (sensors.reset()) {
      Serial.print("good");
    } else {
      if (sensors.busFail()) {
        Serial.print("fail");
      } else {
        Serial.print("empty");
      }
    }
  #endif
}

Resolved. See https://gist.github.com/crcastle/6bab21445c857993d1d8