Low-level nRF24L01(+) register read/write library for Arduino

This is an optimized low-level Arduino library to read and write nRF24L01(+) registers by using a SPI interface. It should be used in combination with a derived class which contains higher level read, write and configuration functionality.

Hardware

Connect the nRF24L01(+) to any Arduino board which contains:

• An internal or external 3.3V regulator.
• A SPI interface.
• 2 digital pins for CE and CSN.

Retransmits or communication loss may occur when connecting the nRF24L01 directly to the 3.3V of an Arduino board, because lots of Arduino boards cannot deliver enough power for the nRF24L01 chip. This can be solved with a separate voltage regulator, or nRF24L01 power adapter.

Schematic Arduino UNO with voltage regulator

A Nordic nRF24L01 or nRF24L01(+) 2.4GHz wireless transceiver connected to an Arduino UNO board with a separate 3.3V voltage regulator and 100uF elco:

Schematic Arduino UNO with nRF24L01+ power adapter

To increase communication reliability, use a nRF24L01 power adapter with a separate 3.3V voltage regulator, such as:

nRF24L01+ Pin	nRF24L01+ Function	nRF24L01+ adapter	Arduino UNO/Mini	Mega2560	ESP8266 NodeMCU
+3.3V	3.3V direct	-	3.3V	3.3V	3.3V
-	+5V via adapter	+5V	+5V	+5V	-
1	GND	GND	GND	GND	GND
3	CE	CE	7	7	D0
4	CSN	CSN	8	8	D8
6	MOSI	MO	11	51	D7
7	MISO	MI	12	50	D6
5	SCK	SCK	13	52	D5

Example

nRF24L01(+) Interface | RegisterAccess

Usage

The CE pin should be controlled inside the derived class.

Library dependencies

The following libraries are used:

• SPI.h

Include file

#include <nRF24L01Iface.h>

Derive nRF24L01Iface class

class nRF24L01Example : nRF24L01Iface
{
public:
    // Constructor, initialize base class with SPI clock and SPI chip-select
    nRF24L01Example(uint32_t spiClock, uint8_t cePin, uint8_t csnPin) :
            nRF24L01Iface(spiClock, csnPin), 
            _cePin(cePin)
    {
    };
    
    // Read status register
    uint8_t readStatus() {
        // Read status register
        return readRegister(REG_STATUS);
    }
  
    // Read from config register
    uint8_t readConfig() {
        // Read config register
        return readRegister(REG_CONFIG);
    }
  
    // Write to config register
    void writeConfig(uint8_t val) {
        // Write to config register
        writeRegister(REG_CONFIG, val);
    }
    
    // Write to TX pipe (0) registers
    void openWritePipe0(const uint8_t *address) {
        // Write 5 Bytes transmit pipe
        // Now pipe 0 cannot be used for receive
        writeRegister(REG_TX_ADDR, address, 5);
    }
    
    // More functions such as read and write 
    // ...
 
private:
    uint8_t _cePin;
};

Create an object from the custom derived class

// CE pin to enable RX and TX modes 
#define CE_PIN      7
  
// SPI chip select pin
#define CSN_PIN     8
  
// Create object and initialize with SPI clock, CE pin and SPI chip-select pin
static nRF24L01Example radio((uint32_t)10000000UL, CE_PIN, CSN_PIN);

Use the class in an application

// Read status register
uint8_t status = radio.readStatus();
  
// Read from config register
uint8_t config = radio.readConfig();
  
// Write to config register
radio.writeConfig(0x08);
  
// Define an address pipe for transmit
const uint8_t pipeAddress[5] = { 0x55, 0xa5, 0x5a, 0xaa, 0x99 };
  
// Configure write pipe0
radio.openWritePipe0(pipeAddress);

Library installation

1. Start the Arduino IDE.
2. Download the latest version from:
   https://github.com/Erriez/ErriezNRF24L01Iface/archive/master.zip
3. Click Sketch | Include Library | Add .ZIP Library... and select this ZIP.
4. Run the example.