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）。

设计思路：基于前面提到的两个节点进行双工通信，树莓派不断的向节点发送数据，为了保证数据发送可以到达，持续发送100ms。

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(22,0,BCM2835_SPI_SPEED_8MHZ);

/********** User Config *********/
// Assign a unique identifier for this node, 0 or 1
bool radioNumber = 1;
bool role = 1;//send 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=27;
unsigned long  srchead=0x00000000;
unsigned long  deshead=0x00010000;
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.openWritingPipe(pipes);
/***********************************/
// This simple sketch opens two pipes for these two nodes to communicate
// back and forth.

radio.stopListening();

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

int node = atoi(argv[1]);
int value = atoi(argv[2]);
cout<<"Node is :"<<node<<",value is "<<value<<" .\n";
// forever loop
while (1)
{
// Pong back role.  Receive each packet, dump it out, and send it back
//
unsigned long data = respData +srchead+deshead;
radio.write(&data,sizeof(unsigned long));
printf("Send Data:size(%d),%lu \n",sizeof(unsigned long),data);
role = 0;
//radio.startListening();
unsigned long end_time = millis();
if((end_time-start_time)>=1000){
break;
}

} // forever loop

return 0;
}

输入指令：sudo ./send_once 1 14,1表示节点号，14表示输入给节点的值。结果如下：

Arduino Leonardo代码

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 = 15;
unsigned long srchead = 0x01;//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 = 0x00;//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(13,OUTPUT);//指示灯
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<<24)+(deshead<<16);
Serial.print("Sending:");
Serial.println(sendData);
digitalWrite(13,HIGH);
bool ok = radio.write(&data,sizeof(unsigned long));

role = 0;
radio.openReadingPipe(1,pipes);
radio.startListening();
start_time = millis();

}
if(!role){
digitalWrite(13,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)>>16;

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&0x0000ffff);
Serial.println("=======================");
sendData++;
}
role = 1;
radio.stopListening();
}else{
unsigned long end_time = millis();
if((end_time-start_time)>=100){
role = 1;
radio.stopListening();
radio.openWritingPipe(pipes);
}
}
}

} // Loop