Mapping gateway coverage using a Things Node

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by JP Meijers

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Posted on Feb. 5, 2018

#Application #PhysicalNetwork #Coverage #Range #TTNMapper

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Introduction

At The Things Conference we ran a workshop on how to contribute coverage measurements to TTN Mapper. To our own shock it is a slight learning curve to get The Things Node up and running. This tutorial will hopefully summarize the steps to follow to get The Things Node (or Uno) ready for mapping with TTN Mapper.

Connect and program the Things Node

You will need a Philips screw driver to open up the Things Node.

Remove the two screws from the back of the Things Node, and remove the back cover. You will see the battery holder that fits 3 AAA batteries, and a micro USB port in the corner. Plug a micro USB cable into the port, and then connect the other end of the cable to your computer.

When the Node is plugged in it should receive power and the light should switch on in either red or green.

In the Arduino IDE go to Tools->Board: and choose SparkFun Pro Micro.

Also under Tools choose Processor ATmega32U4 (3.3V, 8 MHz).

If you are using a Things Uno, choose Arduino Leonardo. The rest of the steps should be the same as for the Things Node.

Then choose Tools->Port and select the port to which the Things Node is connected. The easiest to figure this out is to unplug the Node and see which port disappears. Plug it back in and choose the port that appeared. On Linux the port is mostly called /dev/ttyACM0, but on windows it can be any COM device.

To check if everything is working as expected we are going to program the Blink example into the Node.

Go to File->Examples->01. Basic->Blink. A new window should open pre-filled with some code. Go to Sketch->Upload.

If everything was successful, the light on the Things Node should switch on and off every second. If it is not flashing or working as expected, follow the troubleshooting guide at https://www.thethingsnetwork.org/docs/devices/node/troubleshooting.html

Program the Things Node

You can use any software on the Things Node to use it for mapping. So you do not have to follow this step. The code used here is however the easiest to get it to work.

In the Arduino IDE go to File->Examples->TheThingsNode->Basic. In the window that opens you will see the code for the most basic program to communicate with The Things Network. The program will send a message via TTN every minute, every time the button is pressed or whenever the device is moved.

At the top of the code you will see the following two lines:

const char *appEui = "0000000000000000";
const char *appKey = "00000000000000000000000000000000";

Replace the 0's next to the appEui with the Application EUI you noted down from the device settings screen on the console. Also replace the 0's next to the appKey with the App key from the console.

Lastly replace the TTN_FP_EU868 or REPLACE_ME with the correct frequency plan name, as listed in the line above, for the area you live in.

Make sure the Node is still plugged into your computer. Go to Sketch->Upload.

When you see Done uploading, go to Tools->Serial Monitor. In the serial monitor you will likely see the following output:

Sending: mac join otaa 
Join not accepted: denied
Check your coverage, keys and backend status.
Sending: mac join otaa 
Response is not OK: no_free_ch
Send join command failed

This will continue until you get into range of a gateway, after which the output will change and will be see much less - once a minute at least.

If you are sure you are in range of a gateway, double check that you have copied the Device EUI, Application EUI and App Key. If it still does not work, double check your gateway's configuration. The easiest is to set up your device while you are in range of a gateway that is proven to work.

When everything is working as expected, you should see messages arriving on the TTN Console. Under your device go to Data, and every time the device sends a message, a message should appear on the Data page. If this is working we can continue with the next step.

Using the Android app

This step assumes you have an Android smartphone. If you have an iPhone, skip to the next step.

Download the TTN Mapper app from the Play Store: https://play.google.com/store/apps/details?id=com.jpmeijers.ttnmapper

Optional: Download the TTN Mobile app from the Play Store: https://play.google.com/store/apps/details?id=com.async.ttn

Open the TTN Mapper app. If you see a popup, click on Link Device, or follow the next steps.

Click on the blue circle with three white dots at the bottom left to open the menu. Select Settings.

Click on View and modify linked device.

Click on Log in and select device.

You should see a list of applications that are registered on your TTN account.

Choose the application you created earlier.

Select the device you want to use to map with.

At the top of the Link Device screen you should see all your device configuration filled in.

Click on close and go back to the main screen where you see the map.

At the bottom right you will see a slider switch to enable mapping. Click on this switch.

Most likely the app will now ask you for permissions to use the GPS in your device. Click on configure.

There are three permission types we need. Under each one clikc on Ask For Permission and then Allow.

When you are done click on Continue.

Try to switch on mapping mode again.

The app is now armed. As soon as a packet is received from your device, a circle will be drawn on the map on your phone. If the location of the gateway is known, the circle will be connected to the gateway with a line.

All results will by default be uploaded to ttnmapper.org, and also saved in a logfile on your phone. You can change this from the settings menu.

You can also log into the TTN Mobile app, select your application and device there, and then click on Use with TTN Mapper.