树莓派与Arduino Leonardo使用NRF24L01无线模块通信之基于RF24库 (四) 树莓派单子节点查询

考虑到项目的实际需要，树莓派作为主机，应该只在需要的时候查询特定节点发送的数据，因此接收到数据后需要根据头部判断是否是自己需要的数据，如果不是继续接收数据，超过一定时间未查询到特定节点的数据，则退出程序，避免无限等待。

本项目中各个节点和树莓派的通信不区分信道，因此如果由树莓派发送给特定节点的数据会被所有节点接收到，因此子节点可以判别该数据是否发给自己的，需要在数据的第二个字节中加入目标节点的编号（第一个字节为源节点的编号）。

树莓派代码

如下：

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

using namespace std;

RF24 radio(,,BCM2835_SPI_SPEED_8MHZ);

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

// 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(,);
  // Dump the configuration of the rf unit for debugging
  radio.printDetails();

  radio.openReadingPipe(,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[]);

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

  while(){
    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>>;
        unsigned long data = receData & 0x0000ffff;
        //cout<<"check is "<<check<<"\n";
        if(check==node && (receData & 0x00ff0000)==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)>=){
        cout<<"Wait Data from Node "<<node<<" time out \n";
        break;
    }

  }
  return ;
}

输入指令：sudo ./receive_once 1，参数1表示要查询的节点节点。得到以下结果：

Arduino Leonardo代码

Arduino Leonardo作为子节点，代码与前一节一样，不停发送和接收相互切换。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 = ;

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

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

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

//这个是我们即将建立的传输渠道编码
//!!要和另一个模块的一致
const uint64_t pipes = 0xE8E8F0F0E1LL;

//这个变量会保持我们接受到的信息
//变量类型一定要和传过来的一样
//要传输的数据
unsigned long sendData = ;
unsigned long srchead = 0x01000000;//高16位为头标志，前8位为源节点，后8位为目的节点。根据标志不同区分不同发送源，00为中心主节点
unsigned long deshead = 0x00000000;//高16位为头标志，前8位为源节点，后8位为目的节点。根据标志不同区分不同发送源，00为中心主节点
unsigned long receData;

void setup() {
  pinMode(,OUTPUT);//指示灯
  Serial.begin();
  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(,HIGH);
     bool ok = radio.write(&data,sizeof(unsigned long));

       role = ;
       radio.startListening();
       radio.openReadingPipe(1,pipes);
       start_time = millis();

  }
  if(!role){
     digitalWrite(,LOW);
     if(radio.available()){
         radio.read(&receData,sizeof(unsigned long));

         //根据目标节点，判断是否是发给自己的，如果是，执行相关操作
         unsigned long check = receData & 0x00ff0000;
         if(check == srchead){
            //接收到来自主机的数据，执行相关操作
             Serial.print("Response:");
             Serial.println(receData);
         }
         role = ;
         radio.stopListening();
         radio.openWritingPipe(pipes);
     }else{
        unsigned long end_time = millis();
        if((end_time-start_time)>=){
          role = ;
          radio.stopListening();
          radio.openWritingPipe(pipes);
        }
     }
  }

} // Loop