LoRaWAN and TTN — Arduino L4 · Advaslearning Hub

Learning Goals 5 min

Plain LoRa is two modules talking. LoRaWAN is the protocol that lets thousands of devices share a public network. The Things Network (TTN) is a free, community-run global LoRaWAN with gateways covering ~200 countries. By the end of this lesson you will:

Explain the LoRaWAN three-layer architecture: end-device → gateway → network server.
Register a device on TTN and pick its activation method (OTAA vs ABP).
Decode an uplink message in TTN's console and route it to a webhook or MQTT integration.

Warm-Up 10 min

No hardware required — today is conceptual + a free TTN account.

Check coverage

Visit ttnmapper.org. Search your area. If you see gateway dots, you have free LoRaWAN coverage. If not, you'd need to deploy your own gateway (~£100) or use a different network like Helium / Senet.

New Concept · The LoRaWAN architecture 25 min

Three layers

End-device: your battery-powered Arduino + LoRa module. Sends "uplinks" (data going up) periodically. Sleeps in between.
Gateway: a more capable LoRa receiver, often roof-mounted, with internet connectivity. Forwards every packet it hears to a network server. Doesn't belong to any device — "public" gateway can hear any device near it.
Network server: a cloud service that decrypts and routes messages. TTN is the most popular free one.

Plus the "application": your code or service that consumes the data. Could be a webhook, an MQTT integration, a Node-RED flow, an HTTP endpoint.

Flow of an uplink

End-device packages 10 bytes of sensor data, encrypts with its session key, sends as LoRa packet.
Every gateway in range hears it. Each one forwards to TTN, tagged with its own location + RSSI.
TTN deduplicates (multiple gateways may have heard the same packet), decrypts using the device's key.
TTN routes the decrypted payload to the configured destination — your webhook, MQTT broker, etc.
Your application receives the payload + metadata (which gateways, when, how strong).

Activation: OTAA vs ABP

Method	How	Security	Use
OTAA (Over The Air Activation)	Device joins on first boot with a known DevEUI + AppEUI + AppKey. Network gives it a fresh session key.	Strongest (session keys rotate).	Default. Always pick this unless you have a reason not to.
ABP (Activation By Personalisation)	Session keys are baked into the device's firmware. Skips the join procedure.	Weaker (keys never rotate).	Rare. Useful when you can't wait for the join, or testing.

Device classes

Class	Behaviour	Use
Class A	Mostly asleep. Tx then opens two short Rx windows. Lowest power.	Sensor nodes (default).
Class B	Class A plus periodic scheduled Rx slots.	Devices needing more frequent server commands.
Class C	Continuously listening except while transmitting.	Mains-powered actuators (door locks, valves).

For battery-powered sensors, always Class A.

Setting up a device on TTN

Create a free TTN account at thethingsnetwork.org.
Console → Applications → Create application. Name it.
Add an End Device → Manually (or pick a board if it's in the catalogue).
Pick frequency plan (EU868 / US915 / AS923 etc.) — match your region.
LoRaWAN version: latest (1.0.3 or 1.1).
Activation mode: OTAA.
Note the auto-generated DevEUI, AppEUI (or JoinEUI), AppKey. Copy these into your sketch.

Sketch — using MCCI LMIC library

The most popular Arduino LoRaWAN library. Install via Library Manager ("MCCI LoRaWAN LMIC library").

Configuration is more involved than plain LoRa — you need to set the DevEUI / AppEUI / AppKey, schedule transmissions (respecting duty cycle), handle the join, and parse downlinks. Adafruit and TTN publish example sketches; start from those.

// Skeleton — full LMIC sketches are 200+ lines; this is the shape.
#include <lmic.h>
#include <hal/hal.h>

static const u1_t DEVEUI[8] = { /* from TTN, LSB order */ };
static const u1_t APPEUI[8] = { /* from TTN, LSB order */ };
static const u1_t APPKEY[16] = { /* from TTN, MSB order */ };

void os_getDevEui(u1_t* buf) { memcpy_P(buf, DEVEUI, 8); }
void os_getArtEui(u1_t* buf) { memcpy_P(buf, APPEUI, 8); }
void os_getDevKey(u1_t* buf) { memcpy_P(buf, APPKEY, 16); }

void setup() {
  os_init();
  LMIC_reset();
  LMIC_startJoining();
}

void loop() {
  os_runloop_once();
}

Once joined, you'd call LMIC_setTxData2(port, data, len, confirmed) to queue an uplink. The library handles channel hopping, duty-cycle enforcement, and downlink receipt.

Worked Example · Register and send your first uplink 20 min

Step 1 — set up the TTN application

Follow the steps in §3 above. Get DevEUI / AppEUI / AppKey.

Step 2 — wire and program

Same RFM95 wiring as L04-18. Use the "ttn-otaa-feather-us915-dht22" example (or the EU868 version) from the LMIC library and replace the keys with yours.

Step 3 — observe the join

Serial Monitor shows "Joining..." → "Joined!" within a minute (assuming a gateway is in range).

Step 4 — observe the first uplink

In TTN console → your application → your device → Live data. You'll see incoming packets, with the gateway that received them, RSSI, decoded bytes.

Step 5 — add an integration

TTN → Application → Integrations → MQTT or Webhooks. Configure to forward every uplink to your service. Now your TTN packets land in MQTT (Home Assistant!) or a custom HTTPS endpoint.

Step 6 — send a downlink

From TTN console → your device → Messaging → Downlink. Enter a hex payload. Send. Your device receives on its next Rx window.

Try It Yourself · Mostly paper 15 min

🟢 Q1

The TTN free tier gives you ~30 s of airtime per device per day. SF7 packet ≈ 50 ms. SF12 ≈ 1500 ms. Max daily packets at each SF?

Reveal

SF7: 30 / 0.05 = 600. SF12: 30 / 1.5 = 20. So the choice of SF directly limits your messaging budget.

🟢 Q2

Three gateways hear the same uplink. Does your application see it three times?

Reveal

No. TTN deduplicates server-side. You see one message, with a list of gateways and their RSSIs.

🟡 Q3

Your device sends 1 packet per hour at SF9 (~250 ms per packet). It runs on 2 × AA. Estimate years of life.

Reveal

Per packet: ~100 mA × 0.25 s = 7 µAh. Per hour: 7 µAh (transmit) + 5 µA × 1 h (deep sleep) = 12 µAh / h. Per year: 12 × 8760 ≈ 105 mAh. 2 × AA (~2500 mAh) → ~25 years of LoRa transmissions, limited in practice by battery shelf life (~7–10 years).

🟡 Q4

OTAA vs ABP: pick for (a) factory-deployed sensor (b) urgent prototype with no time for the join procedure.

Reveal

(a) OTAA — security + key rotation. (b) ABP — skips the join, simpler bring-up.

🔴 Q5

You want to send only a 1-bit "alarm" signal. What's the smallest packet payload you can use?

Reveal

1 byte (8 bits, smallest practical). LoRaWAN overhead adds ~13 bytes of headers. The total airtime is what matters; the payload size is mostly aesthetic. Just send {0x01} for alarm-on.

Mini-Challenge · Plan a real deployment 10 min

You want a TTN-connected pet-tracker on your dog's collar. Sends GPS once per 10 minutes. Battery lasts 6 months.

Pick SF (range vs airtime).
Pick activation (OTAA / ABP).
Estimate the battery (capacity vs avg current).
Identify which gateways near you would catch the uplinks (check ttnmapper.org).

Reveal one good answer

SF: SF10 — ~7 km range, ~500 ms airtime. Fits the 6 packets per hour budget.
OTAA — security matters.
Per packet: ~50 µAh. Per day: 144 packets × 50 µAh = 7 mAh. Plus 5 µA × 24 h sleep = 120 µAh. Total ~7 mAh/day → 1500 mAh battery lasts ~200 days = 6+ months. Use an 18650 (3000 mAh) for headroom.
ttnmapper.org will tell you. In most cities, multiple gateways. In rural areas, depends on volunteer deployments.

Recap 5 min

LoRaWAN = LoRa physical + a network layer with gateways + a network server. TTN is the free public option. Register a device on TTN, copy keys into your sketch, use LMIC library, see packets in the console. Tomorrow we leave radio and go industrial: Modbus on RS-485.

LoRaWAN: Network protocol on top of LoRa. Standardised by the LoRa Alliance. Adds encryption, addressing, gateway support.
End-device: Your sensor / actuator. Talks LoRa to gateways.
Gateway: Receiver with internet. Forwards packets to a network server. Doesn't process the contents.
Network server: Cloud service that authenticates devices, decrypts payloads, routes to applications. TTN is the most popular free one.
OTAA / ABP: Activation methods. OTAA = join procedure with key derivation. ABP = static keys.
DevEUI / AppEUI / AppKey: Identifiers and the root key used during OTAA join.
Class A / B / C: Power-vs-listening tradeoffs. Class A = always-sleep, briefly-listen; Class C = always listening.
Uplink / downlink: Device → server / server → device. Uplinks are frequent; downlinks are rare and limited.
LMIC library: The standard Arduino LoRaWAN library. Handles channels, duty cycle, joins.
TTN integrations: Outputs: MQTT, webhooks, Node-RED. Forward uplinks to your service.

Homework 5 min

Make a free TTN account. Browse the gateway map for your area.
If you have LoRa hardware: register a device. Don't worry about uploading the LMIC sketch yet — just the registration is the goal today.
Read ahead to ARD-L04-20 (Modbus and RS-485). Bring an RS-485 transceiver module (MAX485, RS-485 USB adapter for testing) if you have one.

Learning Goals 5 min

Explain the LoRaWAN three-layer architecture: end-device → gateway → network server.
Register a device on TTN and pick its activation method (OTAA vs ABP).
Decode an uplink message in TTN's console and route it to a webhook or MQTT integration.

Warm-Up 10 min

No hardware required — today is conceptual + a free TTN account.

Check coverage

New Concept · The LoRaWAN architecture 25 min

Three layers

End-device: your battery-powered Arduino + LoRa module. Sends "uplinks" (data going up) periodically. Sleeps in between.
Gateway: a more capable LoRa receiver, often roof-mounted, with internet connectivity. Forwards every packet it hears to a network server. Doesn't belong to any device — "public" gateway can hear any device near it.
Network server: a cloud service that decrypts and routes messages. TTN is the most popular free one.

Plus the "application": your code or service that consumes the data. Could be a webhook, an MQTT integration, a Node-RED flow, an HTTP endpoint.

Flow of an uplink

End-device packages 10 bytes of sensor data, encrypts with its session key, sends as LoRa packet.
Every gateway in range hears it. Each one forwards to TTN, tagged with its own location + RSSI.
TTN deduplicates (multiple gateways may have heard the same packet), decrypts using the device's key.
TTN routes the decrypted payload to the configured destination — your webhook, MQTT broker, etc.
Your application receives the payload + metadata (which gateways, when, how strong).

Activation: OTAA vs ABP

Method	How	Security	Use
OTAA (Over The Air Activation)	Device joins on first boot with a known DevEUI + AppEUI + AppKey. Network gives it a fresh session key.	Strongest (session keys rotate).	Default. Always pick this unless you have a reason not to.
ABP (Activation By Personalisation)	Session keys are baked into the device's firmware. Skips the join procedure.	Weaker (keys never rotate).	Rare. Useful when you can't wait for the join, or testing.

Device classes

Class	Behaviour	Use
Class A	Mostly asleep. Tx then opens two short Rx windows. Lowest power.	Sensor nodes (default).
Class B	Class A plus periodic scheduled Rx slots.	Devices needing more frequent server commands.
Class C	Continuously listening except while transmitting.	Mains-powered actuators (door locks, valves).

For battery-powered sensors, always Class A.

Setting up a device on TTN

Create a free TTN account at thethingsnetwork.org.
Console → Applications → Create application. Name it.
Add an End Device → Manually (or pick a board if it's in the catalogue).
Pick frequency plan (EU868 / US915 / AS923 etc.) — match your region.
LoRaWAN version: latest (1.0.3 or 1.1).
Activation mode: OTAA.
Note the auto-generated DevEUI, AppEUI (or JoinEUI), AppKey. Copy these into your sketch.

Sketch — using MCCI LMIC library

The most popular Arduino LoRaWAN library. Install via Library Manager ("MCCI LoRaWAN LMIC library").

// Skeleton — full LMIC sketches are 200+ lines; this is the shape.
#include <lmic.h>
#include <hal/hal.h>

static const u1_t DEVEUI[8] = { /* from TTN, LSB order */ };
static const u1_t APPEUI[8] = { /* from TTN, LSB order */ };
static const u1_t APPKEY[16] = { /* from TTN, MSB order */ };

void os_getDevEui(u1_t* buf) { memcpy_P(buf, DEVEUI, 8); }
void os_getArtEui(u1_t* buf) { memcpy_P(buf, APPEUI, 8); }
void os_getDevKey(u1_t* buf) { memcpy_P(buf, APPKEY, 16); }

void setup() {
  os_init();
  LMIC_reset();
  LMIC_startJoining();
}

void loop() {
  os_runloop_once();
}

Once joined, you'd call LMIC_setTxData2(port, data, len, confirmed) to queue an uplink. The library handles channel hopping, duty-cycle enforcement, and downlink receipt.

Worked Example · Register and send your first uplink 20 min

Step 1 — set up the TTN application

Follow the steps in §3 above. Get DevEUI / AppEUI / AppKey.

Step 2 — wire and program

Same RFM95 wiring as L04-18. Use the "ttn-otaa-feather-us915-dht22" example (or the EU868 version) from the LMIC library and replace the keys with yours.

Step 3 — observe the join

Serial Monitor shows "Joining..." → "Joined!" within a minute (assuming a gateway is in range).

Step 4 — observe the first uplink

In TTN console → your application → your device → Live data. You'll see incoming packets, with the gateway that received them, RSSI, decoded bytes.

Step 5 — add an integration

TTN → Application → Integrations → MQTT or Webhooks. Configure to forward every uplink to your service. Now your TTN packets land in MQTT (Home Assistant!) or a custom HTTPS endpoint.

Step 6 — send a downlink

From TTN console → your device → Messaging → Downlink. Enter a hex payload. Send. Your device receives on its next Rx window.

Try It Yourself · Mostly paper 15 min

🟢 Q1

The TTN free tier gives you ~30 s of airtime per device per day. SF7 packet ≈ 50 ms. SF12 ≈ 1500 ms. Max daily packets at each SF?

Reveal

SF7: 30 / 0.05 = 600. SF12: 30 / 1.5 = 20. So the choice of SF directly limits your messaging budget.

🟢 Q2

Three gateways hear the same uplink. Does your application see it three times?

Reveal

No. TTN deduplicates server-side. You see one message, with a list of gateways and their RSSIs.

🟡 Q3

Your device sends 1 packet per hour at SF9 (~250 ms per packet). It runs on 2 × AA. Estimate years of life.

Reveal

🟡 Q4

OTAA vs ABP: pick for (a) factory-deployed sensor (b) urgent prototype with no time for the join procedure.

Reveal

(a) OTAA — security + key rotation. (b) ABP — skips the join, simpler bring-up.

🔴 Q5

You want to send only a 1-bit "alarm" signal. What's the smallest packet payload you can use?

Reveal

1 byte (8 bits, smallest practical). LoRaWAN overhead adds ~13 bytes of headers. The total airtime is what matters; the payload size is mostly aesthetic. Just send {0x01} for alarm-on.

Mini-Challenge · Plan a real deployment 10 min

You want a TTN-connected pet-tracker on your dog's collar. Sends GPS once per 10 minutes. Battery lasts 6 months.

Pick SF (range vs airtime).
Pick activation (OTAA / ABP).
Estimate the battery (capacity vs avg current).
Identify which gateways near you would catch the uplinks (check ttnmapper.org).

Reveal one good answer

SF: SF10 — ~7 km range, ~500 ms airtime. Fits the 6 packets per hour budget.
OTAA — security matters.
Per packet: ~50 µAh. Per day: 144 packets × 50 µAh = 7 mAh. Plus 5 µA × 24 h sleep = 120 µAh. Total ~7 mAh/day → 1500 mAh battery lasts ~200 days = 6+ months. Use an 18650 (3000 mAh) for headroom.
ttnmapper.org will tell you. In most cities, multiple gateways. In rural areas, depends on volunteer deployments.

Recap 5 min

LoRaWAN: Network protocol on top of LoRa. Standardised by the LoRa Alliance. Adds encryption, addressing, gateway support.
End-device: Your sensor / actuator. Talks LoRa to gateways.
Gateway: Receiver with internet. Forwards packets to a network server. Doesn't process the contents.
Network server: Cloud service that authenticates devices, decrypts payloads, routes to applications. TTN is the most popular free one.
OTAA / ABP: Activation methods. OTAA = join procedure with key derivation. ABP = static keys.
DevEUI / AppEUI / AppKey: Identifiers and the root key used during OTAA join.
Class A / B / C: Power-vs-listening tradeoffs. Class A = always-sleep, briefly-listen; Class C = always listening.
Uplink / downlink: Device → server / server → device. Uplinks are frequent; downlinks are rare and limited.
LMIC library: The standard Arduino LoRaWAN library. Handles channels, duty cycle, joins.
TTN integrations: Outputs: MQTT, webhooks, Node-RED. Forward uplinks to your service.

Homework 5 min

Make a free TTN account. Browse the gateway map for your area.
If you have LoRa hardware: register a device. Don't worry about uploading the LMIC sketch yet — just the registration is the goal today.
Read ahead to ARD-L04-20 (Modbus and RS-485). Bring an RS-485 transceiver module (MAX485, RS-485 USB adapter for testing) if you have one.