动手做！基于nRF24L01P的Arduino无线通信

动手做！基于nRF24L01P的Arduino无线通信笔记。nRF24L01P是一种容易获得的、可接受的无线通信解决方案，在热门硬件上有可直接使用的库，可方便快速地应用于方案原型中。

关键词：nRF24L01+ , Arduino , 无线通信

0.序言

为了帮小崔的毕设解决nRF24L01P的实际使用问题，同时自己也有无线通信的需求（想做一个通用的无线文本显示屏），所以写了这篇记录文章。

1.购买

请注意！一定要根据项目的实际需求，购买价格合理、质量可靠的nRF24L01+。一方面买来的模块直接影响无线传输的速率和丢包率，另一方面，买来的东西要是不好用会直接影响项目的进度和心情的！

这里先记一下我的一次脑抽经历……没时间看的就直接往下拖或者点目录跳过吧

我第一次购买nRF24L01P模块时候是在淘宝上随便搜的，一看，这家店铺牛逼啊！然后一秒下单就不管了。

结果我收到货：

我靠这贴片的尺寸和我想象中的不太一样啊，震惊！然而我没有相应的转接排针

然后我花了整整一晚上的时间：

这玩意这尺寸没法用焊锡什么的……自己的锅自己背吧……

更令我震惊的是，在接下来的例程中，竟然连接正常 = =。不过因为短接的关系，大概不到10分钟它们就烧片阵亡了。。。RIP

所以一定要确认好排针的间距，还有模块的质量（这个也很重要!）

最后还是重新淘宝了新的。

2.软件准备

我使用的库是：

star数800+，支持Python、C++（Arduino和树莓派）。

3.硬件相关

看一下定义

图片取自 http://www.fabacademy.org/archives/2015/eu/students/ciurnelli.mattia/exercise13.html

与板子连接

转自 http://tmrh20.github.io/RF24/

The table below shows how to connect the the pins of the NRF24L01(+) to different boards. CE and CSN are configurable.

对于Arduino Nano型号的板子，其接线方法与UNO相同。其他板子需要查询SPI定义确认一下。

必须注意的是，RF24这个芯片必须接3.3V，接5V将立刻烧毁。切记切记！

接线后如图

4.软件使用

4.1 getstarted

用了大受欢迎的RF24的库，先使用getstarted的例程

/*
* Getting Started example sketch for nRF24L01+ radios
* This is a very basic example of how to send data from one node to another
* Updated: Dec 2014 by TMRh20
*/

#include <SPI.h>
#include "RF24.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(7,8);
/**********************************************************/

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

// Used to control whether this node is sending or receiving
bool role = 0;

void setup() {
  Serial.begin(115200);
  Serial.println(F("RF24/examples/GettingStarted"));
  Serial.println(F("*** PRESS 'T' to begin transmitting to the other node"));
  
  radio.begin();

  // Set the PA Level low to prevent power supply related issues since this is a
 // getting_started sketch, and the likelihood of close proximity of the devices. RF24_PA_MAX is default.
  radio.setPALevel(RF24_PA_LOW);
  
  // Open a writing and reading pipe on each radio, with opposite addresses
  if(radioNumber){
    radio.openWritingPipe(addresses[1]);
    radio.openReadingPipe(1,addresses[0]);
  }else{
    radio.openWritingPipe(addresses[0]);
    radio.openReadingPipe(1,addresses[1]);
  }
  
  // Start the radio listening for data
  radio.startListening();
}

void loop() {
  
  
/****************** Ping Out Role ***************************/  
if (role == 1)  {
    
    radio.stopListening();                                    // First, stop listening so we can talk.
    
    
    Serial.println(F("Now sending"));

    unsigned long start_time = micros();                             // Take the time, and send it.  This will block until complete
     if (!radio.write( &start_time, sizeof(unsigned long) )){
       Serial.println(F("failed"));
     }
        
    radio.startListening();                                    // Now, continue listening
    
    unsigned long started_waiting_at = micros();               // Set up a timeout period, get the current microseconds
    boolean timeout = false;                                   // Set up a variable to indicate if a response was received or not
    
    while ( ! radio.available() ){                             // While nothing is received
      if (micros() - started_waiting_at > 200000 ){            // If waited longer than 200ms, indicate timeout and exit while loop
          timeout = true;
          break;
      }      
    }
        
    if ( timeout ){                                             // Describe the results
        Serial.println(F("Failed, response timed out."));
    }else{
        unsigned long got_time;                                 // Grab the response, compare, and send to debugging spew
        radio.read( &got_time, sizeof(unsigned long) );
        unsigned long end_time = micros();
        
        // Spew it
        Serial.print(F("Sent "));
        Serial.print(start_time);
        Serial.print(F(", Got response "));
        Serial.print(got_time);
        Serial.print(F(", Round-trip delay "));
        Serial.print(end_time-start_time);
        Serial.println(F(" microseconds"));
    }

    // Try again 1s later
    delay(1000);
  }



/****************** Pong Back Role ***************************/

  if ( role == 0 )
  {
    unsigned long got_time;
    
    if( radio.available()){
                                                                    // Variable for the received timestamp
      while (radio.available()) {                                   // While there is data ready
        radio.read( &got_time, sizeof(unsigned long) );             // Get the payload
      }
     
      radio.stopListening();                                        // First, stop listening so we can talk   
      radio.write( &got_time, sizeof(unsigned long) );              // Send the final one back.      
      radio.startListening();                                       // Now, resume listening so we catch the next packets.     
      Serial.print(F("Sent response "));
      Serial.println(got_time);  
   }
 }




/****************** Change Roles via Serial Commands ***************************/

  if ( Serial.available() )
  {
    char c = toupper(Serial.read());
    if ( c == 'T' && role == 0 ){      
      Serial.println(F("*** CHANGING TO TRANSMIT ROLE -- PRESS 'R' TO SWITCH BACK"));
      role = 1;                  // Become the primary transmitter (ping out)
    
   }else
    if ( c == 'R' && role == 1 ){
      Serial.println(F("*** CHANGING TO RECEIVE ROLE -- PRESS 'T' TO SWITCH BACK"));      
       role = 0;                // Become the primary receiver (pong back)
       radio.startListening();
       
    }
  }


} // Loop

注意，使用两个Arduino，每个的通信地址需要不同，每个烧录时使用不同的地址，改动初始化的radioNumber一个为1一个为0，其它不用变，烧进去。

bool radioNumber = 0;

两个都通电后，打开发射端的串口监视器，发送一个T即可开始传输。效果如下

不过我的丢包率有点高啊，可能是买的廉价货的原因。

之前小崔一直实验失败，可能是其接触不良或者面包板的问题。请大家一定不要吝啬，买质量好的线材和元件。

对于一些需求和稳定性的修正，要看一下所有例程，简单看一下注释即可