考慮到項目的實際需要，樹莓派作為主機，應該只在需要的時候查詢特定節點發送的數據，因此接收到數據後需要根據頭部判斷是否是自己需要的數據，如果不是繼續接收數據，超過一定時間未查詢到特定節點的數據，則退出程序，避免無限等待。

本項目中各個節點和樹莓派的通信不區分信道，因此如果由樹莓派發送給特定節點的數據會被所有節點接收到，因此子節點可以判別該數據是否發給自己的，需要在數據的第二個字節中加入目標節點的編號（第一個字節為源節點的編號）。

樹莓派代碼

如下：

#include <cstdlib>
#include <iostream>
#include <sstream>
#include 
 
<string>
#include <unistd.h>
#include <RF24/RF24.h>

using namespace std;

RF24 radio(22,0,BCM2835_SPI_SPEED_8MHZ);

/********** User Config *********/
// Assign a unique identifier for this node, 0 or 1
bool radioNumber = 1;
bool role = 0;//receive mode
unsigned long  start_time=millis();
unsigned 
 
long count=0;
/********************************/

// Radio pipe addresses for the 2 nodes to communicate.
const uint64_t pipes = 0xE8E8F0F0E1LL;

unsigned long  receData;
unsigned long  respData=0x01;
unsigned long  srchead=0x00000000;

int main(int argc, char** argv){

  cout << "RF24/examples/GettingStarted/\n
 
";

  // Setup and configure rf radio
  radio.begin();
  // optionally, increase the delay between retries & # of retries
  radio.setRetries(15,15);
  // Dump the configuration of the rf unit for debugging
  radio.printDetails();
  
  radio.openReadingPipe(1,pipes);
/***********************************/
  // This simple sketch opens two pipes for these two nodes to communicate
  // back and forth.

  radio.startListening();

  cout << "Listening .... \n";

  int node = atoi(argv[1]);

  cout << "Listening Node is : " <<node<<" \n";

  while(1){
    unsigned long end_time = millis();
      if(radio.available()){
        radio.read(&receData,sizeof(unsigned long));
        //cout<<"receData is: "<<receData<<"\n";
        unsigned int check = (unsigned int) receData>>24;
        unsigned long data = receData & 0x00001111;
        //cout<<"check is "<<check<<"\n";

        if(check==node && (receData & 0x00110000)==srchead){
            cout<<"Get Node Data: "<<data<<",Time consume "<<(end_time-start_time)<<"ms \n";
            break;
        }
    }
    
    cout<<"time out is "<<(end_time-start_time)<<"\n";
    if((end_time-start_time)>=5000){
        cout<<"Wait Data from Node "<<node<<" time out \n";
        break;
    }

  }
  return 0;
}

Arduino Leonardo代碼

Arduino Leonardo作為子節點，代碼與前一節一樣，不停發送和接收相互切換。如下：

#include <SPI.h>
#include "RF24.h"
#include <SPI.h>
#include "RF24.h"
#include <printf.h>
/****************** User Config ***************************/
/***      Set this radio as radio number 0 or 1         ***/
bool radioNumber = 0;

/* Hardware configuration: Set up nRF24L01 radio on SPI bus plus pins 7 & 8 */
RF24 radio(9,10);
/**********************************************************/

byte addresses[][6] = {"1Node","2Node"};

// Used to control whether this node is sending or receiving
bool role = 1;//1表示發送模式，0表示接收模式
unsigned long start_time = millis();

//這個是我們即將建立的傳輸渠道編碼
//!!要和另一個模塊的一致
const uint64_t pipes = 0xE8E8F0F0E1LL;
 
//這個變量會保持我們接受到的信息
//變量類型一定要和傳過來的一樣
//要傳輸的數據
unsigned long sendData = 1;
unsigned long srchead = 0x01000000;//高16位為頭標誌，前8位為源節點，後8位為目的節點。根據標誌不同區分不同發送源，00為中心主節點
unsigned long deshead = 0x00000000;//高16位為頭標誌，前8位為源節點，後8位為目的節點。根據標誌不同區分不同發送源，00為中心主節點
unsigned long receData;

void setup() {
  pinMode(13,OUTPUT);//指示燈
  Serial.begin(57600);
  printf_begin();
  Serial.println(F("RF24/examples/GettingStarted"));
  
  radio.begin();

  radio.setPALevel(RF24_PA_MAX);
  radio.openWritingPipe(pipes);
  
}

void loop() {
   Serial.print("role:");
   Serial.println(role);
  if(role){
     unsigned long data = sendData+srchead+deshead;
     Serial.print("Sending:");
     Serial.println(data);
     digitalWrite(13,HIGH);
     bool ok = radio.write(&data,sizeof(unsigned long));

     
       role = 0; 
       radio.startListening();
       start_time = millis();
     
  }
  if(!role){
     digitalWrite(13,LOW);
     if(radio.available()){
         radio.read(&receData,sizeof(unsigned long));
        
         //根據目標節點，判斷是否是發給自己的，如果是，執行相關操作
         unsigned long check = receData & 0x00110000;
         if(check == srchead){
            //接收到來自主機的數據，執行相關操作
             Serial.print("Response:");
             Serial.println(receData);
         }
         role = 1;
         radio.stopListening();
     }else{
        unsigned long end_time = millis();
        if((end_time-start_time)>=100){
          role = 1;
          radio.stopListening();
        }
     }
  }
  
} // Loop

樹莓派與Arduino Leonardo使用NRF24L01無線模塊通信之基於RF24庫 (四) 樹莓派單子節點查詢