Published: February 04, 2019, Edited by: Sara Almeida Santos Daugbjerg

Building devices for The Things Network

Build LoRa node using Arduino Uno and HopeRF RFM95 LoRa transceiver module

  1. Arduino is an open-source electronics platform that is used to sense the real world, make interactive projects and prototypes. Download here:

  2. In this guide you can see how to connect the lora module to arduino, and how to make an antena for it. It explains as well how to make an application in the TTN.

  3. Sara says: I have had problems with the library they refer to in the guide. You can manually instal this library. It worked for me.
    Download it and copy to arduino library directoryon your machine
    Nicolas says: This library from within Arduinos library manager ( Sketch > Include library > Manage library ) worked for me

If using a ESP32

You can wire this way:

Configure LMIC LoRa module pins

const lmic_pinmap lmic_pins = {  
    .nss = 5,
    .rxtx = LMIC_UNUSED_PIN,
    .rst = 14,
    .dio = {2, 25,LMIC_UNUSED_PIN},


  1. Download VCP Driver

  2. Put this line in preferences for additional board manager URLS:

  3. Install the ESP32 board. Choose Tools > Board > Boards manager > search for ESP32, select and click on install.

  4. Open example from the lmic library called ttn_abp

  5. Replace the values marked FILLMEIN with real values from the TTN control panel

  6. Configure LMIC LoRa module pins

//For Heltec Wifi LoRa 32, TTGO LoRa and TTGO LoRa32 V1 use:
const lmic_pinmap lmic_pins = {  
    .nss = 18, 
    .rxtx = LMIC_UNUSED_PIN,
    .rst = 14,
    .dio = {/*dio0*/ 26, /*dio1*/ 33, /*dio2*/ 32}

Copy this code to Payload formats on your device

function Decoder(bytes, port) {  
  // Decode plain text; for testing only 
  return {
      myTestValue: String.fromCharCode.apply(null, bytes)

Arduino - TTN - BME280


Remember to install the libraries

There are two examples you may want to use (File > Examples > MCCI LoraWAN LMIC library) and then either ttn-otaa or ttn-abp. abp is "Activation-by-personalisation" and means you need to specify an address etc. in the code you upload to the ESP32. otaa is "Over-the-air activation" where a DevEUI and application key is configured, which are used in an over-the-air activation procedure where a DevAddr and session keys are assigned/generated automatically for use with all further communication

 * Copyright (c) 2015 Thomas Telkamp and Matthijs Kooijman
 * Permission is hereby granted, free of charge, to anyone
 * obtaining a copy of this document and accompanying files,
 * to do whatever they want with them without any restriction,
 * including, but not limited to, copying, modification and redistribution.
 * This example sends a valid LoRaWAN packet with payload "Hello,
 * world!", using frequency and encryption settings matching those of
 * the The Things Network.
 * This uses ABP (Activation-by-personalisation), where a DevAddr and
 * Session keys are preconfigured (unlike OTAA, where a DevEUI and
 * application key is configured, while the DevAddr and session keys are
 * assigned/generated in the over-the-air-activation procedure).
 * Note: LoRaWAN per sub-band duty-cycle limitation is enforced (1% in
 * g1, 0.1% in g2), but not the TTN fair usage policy (which is probably
 * violated by this sketch when left running for longer)!
 * To use this sketch, first register your application and device with
 * the things network, to set or generate a DevAddr, NwkSKey and
 * AppSKey. Each device should have their own unique values for these
 * fields.
 * Do not forget to define the radio type correctly in config.h.

#include <lmic.h>
#include <hal/hal.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#define SEALEVELPRESSURE_HPA (1013.25)
Adafruit_BME280 bme; // I2C  
unsigned long delayTime;

// LoRaWAN NwkSKey, network session key
// This is the default Semtech key, which is used by the early prototype TTN
// network.
static const PROGMEM u1_t NWKSKEY[16] = { 0xDF, 0x0F, 0x4C, 0xAC, 0xDA, 0xA7, 0xED, 0x34, 0x8A, 0x49, 0x90, 0x99, 0x63, 0x66, 0x01, 0xBF };

// LoRaWAN AppSKey, application session key
// This is the default Semtech key, which is used by the early prototype TTN
// network.
static const u1_t PROGMEM APPSKEY[16] = { 0x4E, 0xCE, 0x5E, 0x1F, 0xCB, 0xED, 0x22, 0x77, 0xD9, 0x7D, 0x96, 0x8F, 0x60, 0x3E, 0x8D, 0xA2 };

// LoRaWAN end-device address (DevAddr)
static const u4_t DEVADDR = 0x260112D5; // <-- Change this address for every node!

// These callbacks are only used in over-the-air activation, so they are
// left empty here (we cannot leave them out completely unless
// DISABLE_JOIN is set in config.h, otherwise the linker will complain).
void os_getArtEui (u1_t* buf) { }  
void os_getDevEui (u1_t* buf) { }  
void os_getDevKey (u1_t* buf) { }

static uint8_t payload[5];  
static osjob_t sendjob;

// Schedule TX every this many seconds (might become longer due to duty
// cycle limitations).
const unsigned TX_INTERVAL = 180;

// Pin mapping
const lmic_pinmap lmic_pins = {  
    .nss = 5,
    .rxtx = LMIC_UNUSED_PIN,
    .rst = 14,
    .dio = {2, 25,LMIC_UNUSED_PIN},

void onEvent (ev_t ev) {  
    Serial.print(": ");
    switch(ev) {
        case EV_SCAN_TIMEOUT:
        case EV_BEACON_FOUND:
        case EV_BEACON_MISSED:
        case EV_BEACON_TRACKED:
        case EV_JOINING:
        case EV_JOINED:
        case EV_RFU1:
        case EV_JOIN_FAILED:
        case EV_REJOIN_FAILED:
        case EV_TXCOMPLETE:
            Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)"));
            if (LMIC.txrxFlags & TXRX_ACK)
              Serial.println(F("Received ack"));
            if (LMIC.dataLen) {
              Serial.println(F("Received "));
              Serial.println(F(" bytes of payload"));
            // Schedule next transmission
            os_setTimedCallback(&sendjob, os_getTime()+sec2osticks(TX_INTERVAL), do_send);
        case EV_LOST_TSYNC:
        case EV_RESET:
        case EV_RXCOMPLETE:
            // data received in ping slot
        case EV_LINK_DEAD:
        case EV_LINK_ALIVE:
            Serial.println(F("Unknown event"));

void do_send(osjob_t* j){  
    // Check if there is not a current TX/RX job running
    if (LMIC.opmode & OP_TXRXPEND) {
        Serial.println(F("OP_TXRXPEND, not sending"));
    } else {
        // read the temperature from the bme280
        float temperature = bme.readTemperature();
        Serial.print("Temperature: "); Serial.print(temperature);
        Serial.println(" *C");
        // adjust for the f2sflt16 range (-1 to 1)
        temperature = temperature / 100; 

        // read the humidity from the bme280
        float rHumidity = bme.readHumidity();
        Serial.print("%RH ");
        // adjust for the f2sflt16 range (-1 to 1)
        rHumidity = rHumidity / 100;

             // float -> int
        // note: this uses the sflt16 datum (
        uint16_t payloadTemp = LMIC_f2sflt16(temperature);
        // int -> bytes
        byte tempLow = lowByte(payloadTemp);
        byte tempHigh = highByte(payloadTemp);
        // place the bytes into the payload
        payload[0] = tempLow;
        payload[1] = tempHigh;

        // float -> int
        uint16_t payloadHumid = LMIC_f2sflt16(rHumidity);
        // int -> bytes
        byte humidLow = lowByte(payloadHumid);
        byte humidHigh = highByte(payloadHumid);
        payload[2] = humidLow;
        payload[3] = humidHigh;

        // Prepare upstream data transmission at the next possible time.
        LMIC_setTxData2(1, payload, sizeof(payload)-1, 0);
        Serial.println(F("Packet queued"));

    // Next TX is scheduled after TX_COMPLETE event.

void setup() {  
    bool status;

    #ifdef VCC_ENABLE
    // For Pinoccio Scout boards
    pinMode(VCC_ENABLE, OUTPUT);
    digitalWrite(VCC_ENABLE, HIGH);

    status = bme.begin(0x76);  
    if (!status) {
        Serial.println("Could not find a valid BME280 sensor, check wiring!");
        while (1);

    Serial.println("-- Default Test --");
    delayTime = 1000;


    // LMIC init
    // Reset the MAC state. Session and pending data transfers will be discarded.

    // Set static session parameters. Instead of dynamically establishing a session
    // by joining the network, precomputed session parameters are be provided.
    #ifdef PROGMEM
    // On AVR, these values are stored in flash and only copied to RAM
    // once. Copy them to a temporary buffer here, LMIC_setSession will
    // copy them into a buffer of its own again.
    uint8_t appskey[sizeof(APPSKEY)];
    uint8_t nwkskey[sizeof(NWKSKEY)];
    memcpy_P(appskey, APPSKEY, sizeof(APPSKEY));
    memcpy_P(nwkskey, NWKSKEY, sizeof(NWKSKEY));
    LMIC_setSession (0x13, DEVADDR, nwkskey, appskey);
    // If not running an AVR with PROGMEM, just use the arrays directly
    LMIC_setSession (0x13, DEVADDR, NWKSKEY, APPSKEY);

    #if defined(CFG_eu868)
    // Set up the channels used by the Things Network, which corresponds
    // to the defaults of most gateways. Without this, only three base
    // channels from the LoRaWAN specification are used, which certainly
    // works, so it is good for debugging, but can overload those
    // frequencies, so be sure to configure the full frequency range of
    // your network here (unless your network autoconfigures them).
    // Setting up channels should happen after LMIC_setSession, as that
    // configures the minimal channel set.
    // NA-US channels 0-71 are configured automatically
    LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(1, 868300000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI);      // g-band
    LMIC_setupChannel(2, 868500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(3, 867100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(4, 867300000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(5, 867500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(6, 867700000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(7, 867900000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
    LMIC_setupChannel(8, 868800000, DR_RANGE_MAP(DR_FSK,  DR_FSK),  BAND_MILLI);      // g2-band
    // TTN defines an additional channel at 869.525Mhz using SF9 for class B
    // devices' ping slots. LMIC does not have an easy way to define set this
    // frequency and support for class B is spotty and untested, so this
    // frequency is not configured here.
    #elif defined(CFG_us915)
    // NA-US channels 0-71 are configured automatically
    // but only one group of 8 should (a subband) should be active
    // TTN recommends the second sub band, 1 in a zero based count.

    // Disable link check validation

    // TTN uses SF9 for its RX2 window.
    LMIC.dn2Dr = DR_SF9;

    // Set data rate and transmit power for uplink (note: txpow seems to be ignored by the library)

    // Start job

void loop() {