Lightweight library for nRF24L01/nRF24L01+ running on AVR architecture (with optional UART)

Bare minimum software developed for nRF24L01/nRF24L01+ RF chip. Software was tested on ATmega328P and ATmega328PB (PB needs few changes in SPI). Can be easily ported to any MCU by adjusting SPI library.

Hardware

nRF24L01+ | ATmega328P  | Arduino UNO
-----------------------------------
  CE      |     PB1     |    D9
  CSN     |     PB2     |    D10
  IRQ     |     PD2     |    D2
  MOSI    |     PB3     |    D11
  MISO    |     PB4     |    D12
  SCK     |     PB5     |    D13

Software

For testing I used both Raspberry Pi to Arduino and Arduino to Arduino. Follow this tutorial to set up Raspberry Pi http://invent.module143.com/daskal_tutorial/raspberry-pi-3-wireless-pi-to-arduino-communication-with-nrf24l01/

Listen to incomming messages

nrf24_start_listening();

By default when there is something on RX register, this ISR gets triggered (PD2 --> IRQ)

ISR(INT0_vect) 

If IRQ won't be used, call

nrf24_available();

which will return 1 if message is ready to be read

if(nrf24_available()) rx_message = nrf24_read_message();

Message can be stored in string array

char rx_message[32];
strcpy(rx_message,nrf24_read_message());

And compared later

if ((strcmp(rx_message,"OFF") == 0)) led_off();

Send message

32 byte (character) message can be sent every ~50ms. After message is sent, it goes back to listening mode.

status = nrf24_send_message(tx_message);

Where 'status' returns '1' on successful send and 'tx_message' is a string set with <string.h>

strcpy(tx_message,"Your message here");

'tx_message' has to be 32 bytes or smaller

Settings

If auto-acknowledgment is disabled, keep in mind that using lower data rates such as 250kbps and 1mbps will lose packets if for example payload exceeds 4 bytes for 250kbps therefore 2mbps should be used. With auto-acknowledgment enabled 250kbps transmits 32 bytes with no problem.

#define DATARATE		RF_DR_2MBPS		// 250kbps, 1mbps, 2mbps
#define POWER			POWER_MAX		// Set power (MAX 0dBm..HIGH -6dBm..LOW -12dBm.. MIN -18dBm)
#define CHANNEL			0x76			// 2.4GHz-2.5GHz channel selection (0x01 - 0x7C)
uint8_t rx_address[5] = { 0xe7, 0xe7, 0xe7, 0xe7, 0xe7 };	// Read pipe address
uint8_t tx_address[5] = { 0xe7, 0xe7, 0xe7, 0xe7, 0xe7 };	// Write pipe address
#define READ_PIPE		0			// Number of read pipe
//
//	-AUTO_ACK can be disabled when running on 2MBPS @ <= 32 byte messages.
//	-250KBPS and 1MBPS with AUTO_ACK disabled lost many packets
//	if the packet size was bigger than 4 bytes.
//	-If AUTO_ACK is enabled, tx_address = rx_address.
//
#define AUTO_ACK		true			// Auto acknowledgment
#define DYN_PAYLOAD		true			// Dynamic payload enabled			
#define CONTINUOUS		false			// Continuous carrier transmit mode (not tested)
//
//	ISR(INT0_vect) is triggered depending on config (only one can be true)
//
#define RX_INTERRUPT	true			// Interrupt when message is received (RX)
#define TX_INTERRUPT	false			// Interrupt when message is sent (TX)
#define RT_INTERRUPT	false			// Interrupt when maximum re-transmits are reached (MAX_RT)
//
//	-PIN map. 
//	-If CE or CSN is changed to different PIN e.g. PC0
//	then change DDRB -> DDRC, PORTB -> PORTC and so on
//
//	CE
#define CE_DDR		DDRB
#define CE_PORT		PORTB
#define CE_PIN		DDB1			// CE connected to PB1
//	CSN
#define CSN_DDR		DDRB
#define CSN_PORT	PORTB
#define CSN_PIN		DDB2			// CSN connected to PB2
//	IRQ
#define IRQ_DDR		DDRD
#define IRQ_PORT	PORTD
#define IRQ_PIN		DDD2			// IRQ connected to PD2

IDE used

Atmel Studio 7 (Version: 7.0.1417)

License

This project is licensed under the MIT License - see the LICENSE file for details