Make it easy!: Arduino Pro mini 3.3v nRF24L01+

nRF24L01+ RF Module has small size, which can be intergrated in IoT application. This PCB operates at 2.4GHz, comnunication by SPI protocol, and power is 3.3V

This article will show how to connect it to Arduino Pro mini, make communication between 2 boards.
Hardware needed:
1. Two PCB Arduino Pro mini https://amzn.to/3adqve0
2. Two PCB nRF24L01+ https://amzn.to/2TmFGKP
3. Power 3.3V https://amzn.to/3a4uycq

1. Arduino Pro Mini

2. nRF24L01+

3. Power module 3.3V

Hardware connection:

Make connection for both Server and Client board.

Software:
There are library call RadioHead which can be download here or here (google share)
After download the library, unzip it, and copy folder RadioHead to Arduino IDE root location (our case is D:\arduino\arduino-1.6.11\libraries\)

Open Arduino IDE, go to File > Examples > RadioHead > nrf24 > nrf24_server

Compile the project and download it to Server board

nrf24_server code

#include <SPI.h>
#include <RH_NRF24.h>

// Singleton instance of the radio driver
RH_NRF24 nrf24;


void setup() 
{
  Serial.begin(9600);
  while (!Serial) 
    ; // wait for serial port to connect. Needed for Leonardo only
  if (!nrf24.init())
    Serial.println("init failed");
  // Defaults after init are 2.402 GHz (channel 2), 2Mbps, 0dBm
  if (!nrf24.setChannel(1))
    Serial.println("setChannel failed");
  if (!nrf24.setRF(RH_NRF24::DataRate2Mbps, RH_NRF24::TransmitPower0dBm))
    Serial.println("setRF failed");    

}

void loop()
{
  if (nrf24.available())
  {
    // Should be a message for us now   
    uint8_t buf[RH_NRF24_MAX_MESSAGE_LEN];
    uint8_t len = sizeof(buf);
    if (nrf24.recv(buf, &len))
    {
//      NRF24::printBuffer("request: ", buf, len);
      Serial.print("got request: ");
      Serial.println((char*)buf);
      
      // Send a reply
      uint8_t data[] = "And hello back to you";
      nrf24.send(data, sizeof(data));
      nrf24.waitPacketSent();
      Serial.println("Sent a reply");
    }
    else
    {
      Serial.println("recv failed");
    }
  }
}

Do it again to open nrf24_client, compile and download for Client board

nrf24_client code

#include <SPI.h>
#include <RH_NRF24.h>

// Singleton instance of the radio driver
RH_NRF24 nrf24;

void setup() 
{
  Serial.begin(9600);
  while (!Serial) 
    ; // wait for serial port to connect. Needed for Leonardo only
  if (!nrf24.init())
    Serial.println("init failed");
  // Defaults after init are 2.402 GHz (channel 2), 2Mbps, 0dBm
  if (!nrf24.setChannel(1))
    Serial.println("setChannel failed");
  if (!nrf24.setRF(RH_NRF24::DataRate2Mbps, RH_NRF24::TransmitPower0dBm))
    Serial.println("setRF failed");    
}


void loop()
{
  Serial.println("Sending to nrf24_server");
  // Send a message to nrf24_server
  uint8_t data[] = "Hello World!";
  nrf24.send(data, sizeof(data));
  
  nrf24.waitPacketSent();
  // Now wait for a reply
  uint8_t buf[RH_NRF24_MAX_MESSAGE_LEN];
  uint8_t len = sizeof(buf);

  if (nrf24.waitAvailableTimeout(500))
  { 
    // Should be a reply message for us now   
    if (nrf24.recv(buf, &len))
    {
      Serial.print("got reply: ");
      Serial.println((char*)buf);
    }
    else
    {
      Serial.println("recv failed");
    }
  }
  else
  {
    Serial.println("No reply, is nrf24_server running?");
  }
  delay(400);
}

Let power both board (by 3.3V source!), using Serial monitor of Arduino IDE to view feed back. If everything normal, feed back should be as following picture:

Arduino Pro mini 3.3v nRF24L01+

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