Building a Wireless Sensor Network with the nRF24L01 Part 6

In part 6 we look at the final hardware design, we switch to the TMRh20 library for the nRF24L01, and we look at a library wrapper that makes getting started with your own wireless sensor network real easy. Go to ForceTronics.com to purchase a wireless flex node and go to Github to access the code and PCB design files.

Click here to get files from Github

Building a Wireless Sensor Network with the nRF24L01 Part 5

In Part 5 of building a wireless sensor network with Arduino and the nRF24L01+ transceiver we take a look at our brand new PCB boards and look at the code for adding the DS18S20 and the STTS751 temperature sensors to the design. You can access the PCB Eagle files and the Arduino code from GitHub: https://github.com/ForceTronics/nRF24L01_Wireless_Sensor_Dev_Board

Building an Arduino Shield and Proto Board for the nRF24L01 Transceiver

The nRF24L01+ Transceiver is a great low cost way to add wireless capability to any project. But the down side of the nRF24L01+ is it can be a hassle to prototype with. In this video we look at how to build an Arduino shield and a mini proto board for the nRF24L01+. You can also purchase the shield and mini proto board covered in the video at forcetronics.com.

To Access the Eagle PCB files:

• Shield: https://github.com/ForceTronics/nRF24L01-Shield
• Mini Proto Board:https://github.com/ForceTronics/nRF24L01-Proto-Board

//*****************************Arduino Code for Transmitter***********************

//This sketch is from a tutorial video on the ForceTronics YouTube Channel. The tutorial discusses how to build a 

//shield and a prototyping board for the nRF24L01 Transceiver Module.

//the code was leverage from Ping pair example at http://tmrh20.github.io/RF24/pingpair_ack_8ino-example.html

//This sketch is free to the public to use and modify at your own risk

#include <SPI.h> //Call SPI library so you can communicate with the nRF24L01+

#include <nRF24L01.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

#include <RF24.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

const int pinCE = 9; //This pin is used to set the nRF24 to standby (0) or active mode (1)

const int pinCSN = 10; //This pin is used to tell the nRF24 whether the SPI communication is a command or message to send out

RF24 wirelessSPI(pinCE, pinCSN); // Create your nRF24 object or wireless SPI connection

const uint64_t pAddress = 0xB00B1E5000LL;   // Radio pipe addresses for the 2 nodes to communicate.

void setup()  

{

  Serial.begin(57600);   //start serial to communicate process

  wirelessSPI.begin();            //Start the nRF24 module

  wirelessSPI.setAutoAck(1);                    // Ensure autoACK is enabled so rec sends ack packet to let you know it got the transmit packet payload

  wirelessSPI.setRetries(5,15);                 // Sets up retries and timing for packets that were not ack'd, current settings: smallest time between retries, max no. of retries

  wirelessSPI.openWritingPipe(pAddress);        // pipe address that we will communicate over, must be the same for each nRF24 module

  wirelessSPI.stopListening();

}

void loop()  

{

   byte t = analogRead(0);//note that we can cast the ADC value to a byte because we know the temp sensor is not going to return a value higher than 255

   if (!wirelessSPI.write(&t, 1 )){  //if the send fails let the user know over serial monitor

       Serial.println("packet delivery failed");      

   }

    delay(1000);

}

//*****************************Arduino Code for Receiver***********************

//This sketch is from a tutorial video on the ForceTronics YouTube Channel. The tutorial discusses how to build a 

//shield and a prototyping board for the nRF24L01 Transceiver Module.

//the code was leverage from Ping pair example at http://tmrh20.github.io/RF24/pingpair_ack_8ino-example.html

//This sketch is free to the public to use and modify at your own risk

#include <SPI.h> //Call SPI library so you can communicate with the nRF24L01+

#include <nRF24L01.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

#include <RF24.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

const int pinCE = 9; //This pin is used to set the nRF24 to standby (0) or active mode (1)

const int pinCSN = 10; //This pin is used to tell the nRF24 whether the SPI communication is a command or message to send out

byte bVal; //used to store ADC value payload from transmit module, the ADC value will be < 256 so it will fit in a byte

RF24 wirelessSPI(pinCE, pinCSN); // Declare object from nRF24 library (Create your wireless SPI) 

const uint64_t pAddress = 0xB00B1E5000LL;  //Create a pipe addresses for the 2 nodes to communicate over, the "LL" is for LongLong type

void setup()   

{

  Serial.begin(57600);  //start serial to communicate process

  wirelessSPI.begin();  //Start the nRF24 module

  wirelessSPI.setAutoAck(1);                    // Ensure autoACK is enabled, this means rec send acknowledge packet to tell xmit that it got the packet with no problems

  wirelessSPI.openReadingPipe(1,pAddress);      //open pipe o for recieving meassages with pipe address

  wirelessSPI.startListening();                 // Start listening for messages

}

void loop()  

{   

   //loop until all of the payload data is recieved, for this example loop should only run once

    while(wirelessSPI.available()){ 

     wirelessSPI.read( &bVal, 1 ); //read one byte of data and store it in bVal variable

     Serial.print("Temperature at transmitter is "); 

     Serial.print(calculateTempF(calculateArduinoVolt(bVal))); //convert the ADC value to a voltage value and than to a temperature value in F

     Serial.println(" F");

    }

 

  delay(200);    

}

//this function calculates temp in F from TMP36 temp sensor

float calculateTempF(float v1) { 

 float temp = 0;

 //calculate temp in C, .75 volts is 25 C. 10mV per degree

 if (v1 < .75) { temp = 25 - ((.75-v1)/.01); } //if below 25 C

 else if (v1 == .75) {temp = 25; }

 else { temp = 25 + ((v1 -.75)/.01); } //if above 25

 //convert to F

 temp =((temp*9)/5) + 32;

 return temp;

}

//This function takes an Arduino analog pin reading and converts it to a voltage value

float calculateArduinoVolt(int val) {

 float volt = (float)val * (5.0 / 1023.0); //convert ADC value to voltage

 return volt;

}

Creating a nRF24L01 Transceiver Network

In this video we will look at how to create an nRF24L01 Transceiver module network (more than two). This is useful if you want to build a wireless sensor network or some type of wireless automation system that has multiple wireless nodes.

***************************Arduino Code for Receiver*******************************
//This sketch is from a tutorial video for networking more than two nRF24L01 tranciever modules on the ForceTronics YouTube Channel
//the code was leverage from the following code http://maniacbug.github.io/RF24/starping_8pde-example.html
//This sketch is free to the public to use and modify at your own risk

#include <SPI.h> //Call SPI library so you can communicate with the nRF24L01+
#include <nRF24L01.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/
#include <RF24.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

const int pinCE = 9; //This pin is used to set the nRF24 to standby (0) or active mode (1)
const int pinCSN = 10; //This pin is used to tell the nRF24 whether the SPI communication is a command or message to send out
byte daNumber = 0; //The number that the transmitters are trying to guess
RF24 wirelessSPI(pinCE, pinCSN); // Declare object from nRF24 library (Create your wireless SPI) 
const uint64_t rAddress[] = {0xB00B1E50D2LL, 0xB00B1E50C3LL};  //Create pipe addresses for the 2 nodes to recieve data, the "LL" is for LongLong type
const uint64_t wAddress[] = {0xB00B1E50B1LL, 0xB00B1E50A4LL};  //Create pipe addresses for the 2 nodes to transmit data, the "LL" is for LongLong type

void setup()   
{
  randomSeed(analogRead(0)); //create unique seed value for random number generation
  daNumber = (byte)random(11); //Create random number that transmitters have to guess
  Serial.begin(57600);  //start serial to communication
  Serial.print("The number they are trying to guess is: "); 
  Serial.println(daNumber); //print the number that they have to guess
  Serial.println();
  wirelessSPI.begin();  //Start the nRF24 module
  wirelessSPI.openReadingPipe(1,rAddress[0]);      //open pipe o for recieving meassages with pipe address
  wirelessSPI.openReadingPipe(2,rAddress[1]);      //open pipe o for recieving meassages with pipe address
  wirelessSPI.startListening();                 // Start listening for messages
}

void loop()  
{   
    byte pipeNum = 0; //variable to hold which reading pipe sent data
    byte gotByte = 0; //used to store payload from transmit module
    
    while(wirelessSPI.available(&pipeNum)){ //Check if recieved data
     wirelessSPI.read( &gotByte, 1 ); //read one byte of data and store it in gotByte variable
     Serial.print("Recieved guess from transmitter: "); 
     Serial.println(pipeNum); //print which pipe or transmitter this is from
     Serial.print("They guess number: ");
     Serial.println(gotByte); //print payload or the number the transmitter guessed
     if(gotByte != daNumber) { //if true they guessed wrong
      Serial.println("Fail!! Try again."); 
     }
     else { //if this is true they guessed right
      if(sendCorrectNumber(pipeNum)) Serial.println("Correct! You're done."); //if true we successfully responded
      else Serial.println("Write failed"); //if true we failed responding
     }
     Serial.println();
    }

  delay(200);    
}

//This function turns the reciever into a transmitter briefly to tell one of the nRF24s
//in the network that it guessed the right number. Returns true if write to module was
//successful
bool sendCorrectNumber(byte xMitter) {
    bool worked; //variable to track if write was successful
    wirelessSPI.stopListening(); //Stop listening, stop recieving data.
    wirelessSPI.openWritingPipe(wAddress[xMitter-1]); //Open writing pipe to the nRF24 that guessed the right number
    if(!wirelessSPI.write(&daNumber, 1))  worked = false; //write the correct number to the nRF24 module, and check that it was recieved
    else worked = true; //it was recieved
    wirelessSPI.startListening(); //Switch back to a reciever
    return worked;  //return whether write was successful
}

***************************Arduino Code for Transmitter 1****************************

//This sketch is from a tutorial video for networking more than two nRF24L01 tranciever modules on the ForceTronics YouTube Channel

//the code was leverage from the following code http://maniacbug.github.io/RF24/starping_8pde-example.html

//This sketch is free to the public to use and modify at your own risk

#include <SPI.h> //Call SPI library so you can communicate with the nRF24L01+

#include <nRF24L01.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

#include <RF24.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

const int pinCE = 9; //This pin is used to set the nRF24 to standby (0) or active mode (1)

const int pinCSN = 10; //This pin is used to tell the nRF24 whether the SPI communication is a command or message to send out

byte counter = 1; //used to count the packets sent

bool done = false; //used to know when to stop sending packets

RF24 wirelessSPI(pinCE, pinCSN); // Create your nRF24 object or wireless SPI connection

const uint64_t wAddress = 0xB00B1E50D2LL;              // Pipe to write or transmit on

const uint64_t rAddress = 0xB00B1E50B1LL;  //pipe to recive data on

void setup()  

{

  Serial.begin(57600);   //start serial to communicate process

  randomSeed(analogRead(0)); //create unique seed value for random number generation

  wirelessSPI.begin();            //Start the nRF24 module

  wirelessSPI.openWritingPipe(wAddress);        //open writing or transmit pipe

  wirelessSPI.openReadingPipe(1,rAddress);  //open reading or recieve pipe

  wirelessSPI.stopListening(); //go into transmit mode

}

void loop()  

{

   if(!done) { //true once you guess the right number

     byte randNumber = (byte)random(11); //generate random guess between 0 and 10

   

    if (!wirelessSPI.write( &randNumber, 1 )){  //if the write fails let the user know over serial monitor

         Serial.println("Guess delivery failed");      

     }

     else { //if the write was successful 

          Serial.print("Success sending guess: ");

          Serial.println(randNumber);

       

        wirelessSPI.startListening(); //switch to recieve mode to see if the guess was right

        unsigned long startTimer = millis(); //start timer, we will wait 200ms 

        bool timeout = false; 

        while ( !wirelessSPI.available() && !timeout ) { //run while no recieve data and not timed out

          if (millis() - startTimer > 200 ) timeout = true; //timed out

        }

    

        if (timeout) Serial.println("Last guess was wrong, try again"); //no data to recieve guess must have been wrong

        else  { //we recieved something so guess must have been right

          byte daNumber; //variable to store recived value

          wirelessSPI.read( &daNumber,1); //read value

          if(daNumber == randNumber) { //make sure it equals value we just sent, if so we are done

            Serial.println("You guessed right so you are done");

            done = true; //signal to loop that we are done guessing

          }

          else Serial.println("Something went wrong, keep guessing"); //this should never be true, but just in case

        }

        wirelessSPI.stopListening(); //go back to transmit mode

      

     }

   }

    delay(1000);

}

***************************Arduino Code for Transmitter 2****************************

//This sketch is from a tutorial video for networking more than two nRF24L01 tranciever modules on the ForceTronics YouTube Channel

//the code was leverage from the following code http://maniacbug.github.io/RF24/starping_8pde-example.html

//This sketch is free to the public to use and modify at your own risk

#include <SPI.h> //Call SPI library so you can communicate with the nRF24L01+

#include <nRF24L01.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

#include <RF24.h> //nRF2401 libarary found at https://github.com/tmrh20/RF24/

const int pinCE = 9; //This pin is used to set the nRF24 to standby (0) or active mode (1)

const int pinCSN = 10; //This pin is used to tell the nRF24 whether the SPI communication is a command or message to send out

bool done = false; //used to know when to stop sending guesses

RF24 wirelessSPI(pinCE, pinCSN); // Create your nRF24 object or wireless SPI connection

const uint64_t wAddress = 0xB00B1E50C3LL;  //pipe for writing or transmitting data

const uint64_t rAddress = 0xB00B1E50A4LL;  //pipe for reading or recieving data

void setup()  

{

  Serial.begin(57600);   //start serial to communicate process

  randomSeed(analogRead(0)); //create unique seed value for random number generation

  wirelessSPI.begin();            //Start the nRF24 module

  wirelessSPI.openWritingPipe(wAddress);    // setup pipe to transmit over

  wirelessSPI.openReadingPipe(1,rAddress);  //set up pipe to recieve data

  wirelessSPI.stopListening();  //turn off recieve capability so you can transmit

}

void loop()  

{

  if(!done) { //true once you guess the right number

     byte randNumber = (byte)random(11); //generate random guess between 0 and 10

   

    if (!wirelessSPI.write( &randNumber, 1 )){  //if the write fails let the user know over serial monitor

         Serial.println("Guess delivery failed");      

     }

     else { //if the write was successful 

          Serial.print("Success sending guess: ");

          Serial.println(randNumber);

       

        wirelessSPI.startListening(); //switch to recieve mode to see if the guess was right

        unsigned long startTimer = millis(); //start timer, we will wait 200ms 

        bool timeout = false; 

        while ( !wirelessSPI.available() && !timeout ) { //run while no recieve data and not timed out

          if (millis() - startTimer > 200 ) timeout = true; //timed out

        }

    

        if (timeout) Serial.println("Last guess was wrong, try again"); //no data to recieve guess must have been wrong

        else  { //we recieved something so guess must have been right

          byte daNumber; //variable to store recived value

          wirelessSPI.read( &daNumber,1); //read value

          if(daNumber == randNumber) { //make sure it equals value we just sent, if so we are done

            Serial.println("You guessed right so you are done");

            done = true; //signal to loop that we are done guessing

          }

          else Serial.println("Something went wrong, keep guessing"); //this should never be true, but just in case

        }

        wirelessSPI.stopListening(); //go back to transmit mode

      

     }

   }

    delay(1000);

}