Tag Archives: ttn

TheThingsNetwork LoRa node with ESP8266 and RN2483

TheThingsNetwork is a global community with a mission of bringing the Internet Of Things world closer to the people and making the connectivity easy and completely free. It’s doing that by providing open to use communication base stations and distributed back end system that handles all the communication, security and data availability throughout your devices and target system.

The communication protocol used is LoRaWAN. It allows low powered devices to connect from far distances, having in mind that they can only send or receive short bursts of data every now and then. The communication works on open frequencies, meaning that they don’t rely on regulators or major telecommunication providers.

Recently I applied for a local TTN community in Skopje, which got approved and the infrastructure is still in development. For the first test subject, I used Arduino Uno combined with the Microchip RN2483 for LoRaWAN connectivity. It’s the most basic example and it worked just fine. However the real requirement is to have an ESP8266 main controller that will talk to the RN2483. The reason for this is, that the case I’m working on needs an end-user configuration mechanism, and the ESP’s integrated WiFi and WebServer are just the thing.

For convenience and easier prototyping, I used the NodeMCU devkit board which is based on ESP-12E chip. It resembles Arduino quite much, has direct micro USB connection removing the need for FTDI and has all the pins necessary to connect the RN2483 chip and additional sensors / actuators you’ll need. For development, you can use the Arduino IDE and SDK with the ESP8266 boards and port. I’ve written on this topic before here (it may be a bit outdated though…).

Part 1: Connecting the parts

For a very basic setup, you’ll be needing a proto PCB (or a protoboard if you don’t wan’t to solder everything just yet), NodeMCU 1.0 devkit, RN2483 chip, some patch wires, solid core wire to act as an antenna, and soldering wire.

The NodeMCU has a bigger form factor than the RN2483 chip, so it’s possible even to solder them tightly together or one under the other by using some header pins aside.

The connection between the two goes like this:

RN2483 TX (6) <-> NodeMCU D6
RN2483 RX (7) <-> NodeMCU D5
RN2483 VDD (12 or 34) <-> NodeMCU 3.3V
RN2483 GND (20 or 33 …) <-> NodeMCU GND
RN2483 RESET (32) <-> NodeMCU D7
RN2483 RFH (23) <-> Antenna or 8.6cm solid core wire

My gruesome implementation looks like this:

NodeMCU + RN2483 side    NodeMCU + RN2483 top

Part 2: Prepare a TTN app

Go to TheThingsNetwork and create an account if you don’t have one. Check afterwards in your local community whether you have LoRa TTN coverage in your area.

After that, go to the staging app and create a new application. Choose Activate Devices with default app key in order to be able to use OTAA (this is not mandatory, I’m just using OTAA in the example code). When the app is created, take the App EUI and in Settings get the Default App Key. You’ll be needing them in the code afterwards. Leave the main app page opened, so that you can see the connections and the data sent afterwards.

Part 3: Code

Before you go off coding, first do some preparations:
– get the latest Arduino IDE
– install the nodemcu devkit driver
– install the esp8266 board in the Boards manager (or update to the latest)
– install the RN2483 library
– install the ESPSoftwareSerial library

The code I’m using is a modification of this nice tutorial done by jpmeiers.

*) this is the bare minimum you need in order to start things working. I got it by modifying the original code and removing the other parts afterwards, so let me know if something is not right.

When you got all packed, choose NodeMCU to be your current board, fire the serial monitor, set it to 57600 baud rate, and flash the code to the device. If everything is fine, you should see nice messages in the serial log, and by refreshing the app page on ttn, you should see your device registered and messages arriving every minute.

Part extra: extend and pack

The final product I made with all this is a Dust, Temperature and humidity TTN sensor node. You can do that by combining DHT22 (tutorial here) and sharp dust sensor (arduino tutorial here). However, the code still looks a bit shaky, and the dust sensor might need some extra work and/or calibration, so I don’t dare yet to publish it.

Dust, Temperature and Humidity LoRa TTN Sensor
The final sensor node prototype

And as a final touch, I designed a custom enclosure in OpenSCAD (a mix of this design by b2vn) and I 3D printed it. I just made it longer and wider, and put holes for the DHT and the dust sensor opening, to have air circulating.

The final result:

Dust, Humidity and temperature TTN sensor node with 3d printed housing
Dust, Humidity and temperature TTN sensor node with 3d printed housing