LoRa-RF Arduino Library

Arduino LoRa-RF library used for transmitting and receiving data using LoRa module with Semtech SX126x series, SX127x series, or LLCC68. The library works by interfacing SPI port and some I/O pins. Support for configuring frequency, modulation parameter, transmit power, receive gain and other RF parameters on both LoRa and FSK modulation also support for handling transmit and receive using interrupt signal.

This readme is written for quick start guide. Visit this link for complete documentation.

Hardware Compatibility

Theoritically all LoRa modules using SX126x series (SX1261, SX1262, SX1268), SX127x series (SX1272, SX1276, SX1277, SX1278, SX1279), or LLCC68 will compatible using this library. Arduino LoRa development board which interfaced using SPI to a LoRa module also theoritically compatible.

Some LoRa module which already tested and confirmed compatible are:

• Ebyte: E19-433M20SC, E19-915M20S, E19-433M30S, E19-915M30S, E22-400M22S, E22-900M22S, E22-400M30S, E22-900M30S
• HopeRF: RFM95W, RFM96W, RFM98W

Please note that LoRa modules use 3.3V for power supply and I/O ports. Care must me taken for connecting 5V arduino to LoRa module.

Installation

Using the Arduino IDE Library Manager

1. Choose Sketch -> Include Library -> Manage Libraries...
2. Type LoRaRF into the search box.
3. Search a row with title LoRaRF by Chandra Wijaya.
4. Click the Install button to install the library.

Using Git

Open terminal, Git bash, or command prompt in Arduino library folder then run following command. Default library folder for windows is C:\Users\{username}\Documents\Arduino and for linux is ~/Documents/Arduino/libraries/.

git clone https://github.com/chandrawi/LoRaRF-Arduino.git

Initialization

To work with the library, first you must include SX126x header or SX127x header depending LoRa module you use. For LLCC68 include SX126x header. Then initialize class in the header by creating an object.

// for SX126x series or LLCC68
#include <SX126x.h>
SX126x LoRa;

// for SX127x series
#include <SX127x.h>
SX127x LoRa;

Before calling any configuration methods, doing transmit or receive operation you must call begin() method. You can call begin() method inside Arduino setup() function.

void setup() {
  LoRa.begin();
  // configuration code goes here
}

void loop() {
  // transmit and receive operation goes here
}

Hardware Configuration

Wiring Connections

Power pins, SPI pins, and RESET pin must be connected between arduino and LoRa module. For SX126x series and LLCC68, a BUSY pin also must be connected. If you want to use interrupt operation, you can connect DIO0 for SX127x series and one of DIO1, DIO2, or DIO3 pin for SX126x series. You also should connect TXEN and RXEN pins if your LoRa module have those pins.

The default Arduino pins used for connecting to SX126x and SX127x are as follows.

Semtech SX126x	Semtech SX127x	Arduino
VCC	VCC	3.3V
GND	GND	GND
SCK	SCK	SCK
MISO	MISO	MISO
MOSI	MOSI	MOSI
NSS	NSS	10
RESET	RESET	9
BUSY		4
DIO1	DIO0	-1 (unused)
TXEN	TXEN	-1 (unused)
RXEN	RXEN	-1 (unused)

SPI Port Configuration

To change Arduino default SPI port or SPI frequency call setSPI() method before begin() method.

LoRa.setSPI(SPI2, 16000000);
LoRa.begin();

I/O Pins Configuration

To configure I/O pins (NSS, RESET, BUSY, IRQ, TXEN, RXEN pin) call setPins() before begin() method.

// set NSS->10, RESET->9, BUSY->4, DIO1->2, TXEN->8, RXEN->7 for SX126x series
LoRa.setPins(10, 9, 2, 4, 8, 7);
// set NSS->10, RESET->9, DIO0->2, TXEN->8, RXEN->7 for SX127x series
LoRa.setPins(10, 9, 2, 8, 7);
LoRa.begin();

Modem Configuration

Before transmit or receive operation you can configure transmit power and receive gain or matching frequency, modulation parameter, packet parameter, and synchronize word with other LoRa device you want communicate.

Transmit Power

// set transmit power to +22 dBm for SX1262
LoRa.setTxPower(22, SX126X_TX_POWER_SX1262);
// set transmit power to +20 dBm for SX127x series using boost pin
LoRa.setTxPower(20, SX127X_TX_POWER_PA_BOOST);

Receive Gain

// set receive gain to power saving
LoRa.setRxGain(LORA_RX_GAIN_POWER_SAVING);
// set receive gain to boosted and AGC on for SX127x series
LoRa.setRxGain(LORA_RX_GAIN_BOOSTED, true);

Frequency

// Set frequency to 915 Mhz
LoRa.setFrequency(915000000);

Modulation Parameter

// set spreading factor 8, bandwidth 125 kHz, coding rate 4/5, and low data rate optimization off
LoRa.setLoRaModulation(8, 125000, 5, false);

Packet Parameter

// set explicit header mode, preamble length 12, payload length 15, CRC on and no invert IQ operation
LoRa.setLoRaPacket(LORA_HEADER_EXPLICIT, 12, 15, true, false);

Synchronize Word

// Set syncronize word for public network (0x3444)
LoRa.setSyncWord(0x3444);

Transmit Operation

Transmit operation begin with calling beginPacket() method following by write() method to write package to be tansmitted and ended with calling endPacket() method. For example, to transmit "HeLoRa World!" message and an increment counter you can use following code.

// message and counter to transmit
char message[] = "HeLoRa World!";
uint8_t counter = 0;

LoRa.beginPacket();
LoRa.write(message, sizeof(message)); // write multiple bytes
LoRa.write(counter++);                // write single byte
LoRa.endPacket();
LoRa.wait();

For more detail about transmit operation, please visit this link.

Receive Operation

Receive operation begin with calling request() method following by read() method to read received package. available() method can be used to get length of remaining package. For example, to receive message and a counter in last byte you can use following code.

LoRa.request();
LoRa.wait();

// get message and counter in last byte
const uint8_t length = LoRa.available() - 1;
char message[length];
uint8_t i=0;
while (LoRa.available() > 1){
  message[i++] = LoRa.read();         // read multiple bytes
}
uint8_t counter = LoRa.read();        // read single byte

For more detail about receive operation, please visit this link.

Examples

See examples for SX126x, SX127x, and simple network implementation.

Contributor

Chandra Wijaya Sentosa <chandra.w.sentosa@gmail.com>