nRF24L01 Driver Documentation

Introduction

This is a comprehensive driver library for the nRF24L01 2.4GHz wireless transceiver module, designed specifically for STM32 microcontrollers using the HAL library.

Key Features

• Full register-level control of nRF24L01 functionality
• Support for all 6 data pipes with individual configuration
• Auto-acknowledgment and auto-retransmission
• Dynamic payload lengths
• Payload with ACK capability
• Configurable RF power levels and data rates
• Comprehensive interrupt handling
• Easy-to-use high-level API functions

Basic Usage

Initialization

#include "nrf24l01.h"
 
// Get default configuration
nrf24l01_device nrf = nrf24l01_get_default_config();
 
// Configure hardware connections
nrf.spi = &hspi1;          // SPI handle
nrf.ce_port = GPIOA;       // CE pin port
nrf.ce_pin = 8;            // CE pin number
nrf.csn_port = GPIOA;      // CSN pin port
nrf.csn_pin = 9;           // CSN pin number
nrf.irq_port = GPIOA;      // IRQ pin port (optional)
nrf.irq_pin = 10;          // IRQ pin number (optional)
nrf.timer = &htim2;        // Timer for microsecond delays
 
// Initialize the device
if (nrf24l01_init(&nrf) == 0) {
    // Initialization successful
}

Transmitter Setup

// Configure transmit address
uint8_t tx_address[] = {0xE7, 0xE7, 0xE7, 0xE7, 0xE7};
nrf.transmit_address = tx_address;
nrf24l01_write_register(&nrf, TX_ADDR, nrf.transmit_address, 5);
 
// Configure data pipe 0 for auto-ack (must match TX address)
nrf24l01_data_pipe_address(&nrf, 0, nrf.transmit_address, 5);
nrf24l01_data_pipe_enable(&nrf, 0, 1);
nrf24l01_data_pipe_auto_ack(&nrf, 0, 1);
nrf24l01_data_pipe_payload_width(&nrf, 0, 32);
 
// Send data
uint8_t data[] = "Hello nRF24L01!";
nrf24l01_write_tx_payload(&nrf, data, sizeof(data)); // write payload to TX FIFO
nrf24l01_transmit(&nrf); // put device in TX Mode

Receiver Setup

// Configure receive address for pipe 1
uint8_t rx_address[] = {0xE7, 0xE7, 0xE7, 0xE7, 0xE7};
nrf24l01_data_pipe_address(&nrf, 1, rx_address, 5);
nrf24l01_data_pipe_enable(&nrf, 1, 1);
nrf24l01_data_pipe_auto_ack(&nrf, 1, 1);
nrf24l01_data_pipe_payload_width(&nrf, 1, 32);
 
// make the device PRX
uint8_t config_register = 0;
nrf24l01_read_register(&nrf, CONFIG, &config_register, 1);
config_register |= PRX;
nrf24l01_wrtie_register(&nrf, CONFIG, &config_register, 1);
 
// Listen to new available packets
nrf24l01_listen(&nrf);
 
// Check for received data
uint8_t status = nrf24l01_nop(&nrf);
do {
if (status & RX_DR) {
    uint8_t received_data[32];
    nrf24l01_read_rx_payload(&nrf, received_data, 32);
    nrf24l01_clear_interrupt_flag(&nrf, nrf24l01_irq_rx_data_ready);
    break;
}
status = nrf24l01_nop(&nrf);
}while(1);

Configuration Options

The driver supports extensive configuration options:

• RF Channel: 0-125 (2.400-2.525 GHz)
• Data Rate: 1 Mbps or 2 Mbps
• Output Power: -18, -12, -6, or 0 dBm
• Address Width: 3, 4, or 5 bytes
• Auto Retransmit: Configurable delay (250µs-4ms) and count (0-15)
• Payload Length: Fixed (1-32 bytes) or dynamic

Advanced Features

Dynamic Payload Length

// Enable dynamic payload length globally
nrf24l01_dynamic_payload_length(&nrf, 1);
 
// Enable for specific pipes
nrf24l01_data_pipe_dynamic_payload_length(&nrf, 0, 1);
nrf24l01_data_pipe_dynamic_payload_length(&nrf, 1, 1);

ACK Payloads

// Enable payload with ACK feature
nrf24l01_payload_with_ack(&nrf, 1);
 
// Write ACK payload for pipe 1
uint8_t ack_data[] = "ACK";
nrf24l01_write_ack_payload(&nrf, ack_data, 1, sizeof(ack_data));

Troubleshooting

Common issues and solutions:

• No communication: Check SPI connections and timing
• Transmission fails: Verify addresses match between TX and RX
• High packet loss: Adjust RF power level or channel
• Interrupt not working: Ensure IRQ pin is configured and interrupt flags are cleared

License

This driver is provided as-is for educational and commercial use.

Author

Trần Minh Khải

Date

September 18, 2025

Version

1.0