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Wednesday, December 21, 2016

GPS data upload and visualization using LinkIt ONE and Thingsboard

Thingsboard is an open-source server-side platform that allows you to monitor and control IoT devices. It is free for both personal and commercial usage and you can deploy it anywhere. If this is your first experience with the platform we recommend to review what-is-thingsboard page and getting-started guide.

This sample application shows capability to track GPS location of LinkIt ONE device and further visualization on the map. It performs collection of latitude and longitude values produced by GPS module. Collected data is pushed to Thingsboard for storage and visualization. The purpose of this application is to demonstrate Thingsboard data collection API and visualization capabilities.

The GPS module is built-in module of LinkIt ONE. LinkIt ONE pushes data to Thingsboard server via MQTT protocol by using PubSubClient library for Arduino. Data is visualized using map widget which is part of customizable dashboard. The application that is running on LinkIt ONE is written using Arduino SDK which is quite simple and easy to understand.

Once you complete this sample/tutorial, you will see your device GPS and battery data on the following dashboard.



You will need to Thingsboard server up and running. Use either Live Demo or Installation Guide to install Thingsboard.

This tutorial was prepared for Windows OS users. However it is possible to run it on other OS (Linux or MacOS).

List of hardware

  • LinkIt One

    GPS and WIFI Antenna are shipped with board.

Thingsboard configuration

Note Thingsboard configuration steps are necessary only in case of local Thingsboard installation. If you are using Live Demo instance all entities are pre-configured for your demo account. However, we recommend to review this steps because you will still need to get device access token to send requests to Thingsboard.

Provision your device

This step contains instructions that are necessary to connect your device to Thingsboard.

Open Thingsboard Web UI (http://localhost:8080) in browser and login as tenant administrator

Goto “Devices” section. Click “+” button and create device with name “LinkIt One Demo Device”.


Once device created, open its details and click “Manage credentials”.

Copy auto-generated access token from the “Access token” field. Please save this device token. It will be referred to later as $ACCESS_TOKEN.


Click “Copy Device ID” in device details to copy your device id to clipboard. Paste your device id to some place, this value will be used in further steps.

Provision your dashboard

This step contains instructions that are necessary to provision new dashboard with map widgets to Thingsboard.

Open “Docker Quickstart Terminal” and download file containing demo dashboard JSON:

curl -L > linkit_one_gps_dashboard.json

Update dashboard configuration with your device Id (obtained in previous step) by issuing the following command:

sed -i "s/{DEVICE_ID}/<your device id>/" linkit_one_gps_dashboard.json

Obtain JWT token by issuing login POST command:

curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' -d '{"username":"[email protected]", "password":"tenant"}' 'http://localhost:8080/api/auth/login'

You will receive response in the following format:

{"token":"$YOUR_JSON_TOKEN", "refreshToken": "$REFRESH_TOKEN"}

copy $YOUR_JSON_TOKEN to some place. Note that it will be valid for 15 minutes by default.

Execute dashboard upload command:

curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'X-Authorization: Bearer $YOUR_JSON_TOKEN' -d "@linkit_one_gps_dashboard.json" 'http://localhost:8080/api/dashboard'

Programming the LinkIt One device

If you already familiar with basics of LinkIt One programming using Arduino IDE you can skip the following step and proceed with step 2.

Step 1. LinkIt ONE and Arduino IDE setup.

In order to start programming LinkIt One device you will need Arduino IDE installed and all related libraries. Please follow this guide in order to install the Arduino IDE and LinkIt One SDK:

It’s recommended to update your firmware by following this guide. To try your first LinkIt One sample, please follow this guide.

Step 2. PubSubClient library installation.

Open Arduino IDE and go to Sketch -> Include Library -> Manage Libraries. Find PubSubClient by Nick O’Leary and install it.

Note that this tutorial was tested with PubSubClient 2.6.

Download and open gps_tracker.ino sketch.

Note You need to edit following constants and variables in the sketch:

  • WIFI_AP - name of your access point
  • WIFI_PASSWORD - access point password
  • WIFI_AUTH - choose one of LWIFI_OPEN, LWIFI_WPA, or LWIFI_WEP.
  • TOKEN - the $ACCESS_TOKEN from Thingsboard configuration step.
  • thingsboardServer - Thingsboard HOST/IP address that is accessable within your wifi network. Specify “” if you are using live demo server.
#include <PubSubClient.h>

#include <LWiFi.h>
#include <LWiFiClient.h>
#include <LGPS.h>
#include <LBattery.h>



gpsSentenceInfoStruct gpsInfo;

char thingsboardServer[] = "YOUR_THINGSBOARD_HOST_OR_IP";

LWiFiClient wifiClient;

PubSubClient client( wifiClient );

unsigned long lastSend;

void setup()
  Serial.println("GPS started.");
  client.setServer( thingsboardServer, 1883 );
  lastSend = 0;

void loop()
  LWifiStatus ws = LWiFi.status();
  boolean status = wifi_status(ws);
  if (!status) {
    Serial.println("Connecting to AP ...");
    while (0 == LWiFi.connect(WIFI_AP, LWiFiLoginInfo(WIFI_AUTH, WIFI_PASSWORD)))
    Serial.println("Connected to AP");

  if ( !client.connected() ) {

  if ( millis() - lastSend > 1000 ) { // Update and send only after 1 seconds
    lastSend = millis();



void getAndSendGPSData()
  Serial.println("Collecting GPS data.");

  char latitude[20];
  char lat_direction[1];
  char longitude[20];
  char lon_direction[1];
  char buf[20];
  char time[30];

  const char* p = (char*)gpsInfo.GPGGA;

  p = nextToken(p, 0); // GGA
  p = nextToken(p, time); // Time
  p = nextToken(p, latitude); // Latitude
  p = nextToken(p, lat_direction); // N or S?
  p = nextToken(p, longitude); // Longitude
  p = nextToken(p, lon_direction); // E or W?
  p = nextToken(p, buf); // fix quality

  const int coord_size = 8;
  char lat_fixed[coord_size], lon_fixed[coord_size];
  convertCoords(latitude, longitude, lat_direction, lon_direction, lat_fixed, lon_fixed, coord_size);



  if (buf[0] == '1')
    // GPS fix
    p = nextToken(p, buf); // number of satellites
    Serial.print("GPS is fixed:");
    Serial.println(" satellite(s) found!");
    Serial.println("GPS is not fixed yet.");

  // Obtain battery level
  String batteryLevel = String(LBattery.level());
  String batteryCharging = LBattery.isCharging() == 1 ? "true" : "false";

  // Just debug messages
  Serial.print( "Sending gps location and battery level: [" );
  Serial.print( lat_fixed ); Serial.print( lon_fixed );
  Serial.print(" Battery level: "); Serial.print( batteryLevel );
  Serial.print(" Battery charging: "); Serial.print( batteryCharging );
  Serial.print( "]   -> " );

  // Prepare a JSON payload string
  String payload = "{";
  payload += "\"latitude\":"; payload += lat_fixed; payload += ", ";
  payload += "\"longitude\":"; payload += lon_fixed; payload += ", ";
  payload += "\"batteryLevel\":"; payload += batteryLevel;  payload += ", ";
  payload += "\"batteryCharging\":"; payload += batteryCharging;
  payload += "}";

  // Send payload
  char attributes[100];
  payload.toCharArray( attributes, 100 );
  client.publish( "v1/devices/me/attributes", attributes );
  Serial.println( attributes );

void InitLWiFi()
  // Keep retrying until connected to AP
  Serial.println("Connecting to AP ...");
  while (0 == LWiFi.connect(WIFI_AP, LWiFiLoginInfo(WIFI_AUTH, WIFI_PASSWORD))) {
  Serial.println("Connected to AP");

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Connecting to Thingsboard node ...");
    // Attempt to connect (clientId, username, password)
    if ( client.connect("LinkIt One Device", TOKEN, NULL) ) {
      Serial.println( "[DONE]" );
    } else {
      Serial.print( "[FAILED] [ rc = " );
      Serial.print( client.state() );
      Serial.println( " : retrying in 5 seconds]" );
      // Wait 5 seconds before retrying
      delay( 5000 );

void convertCoords(const char* latitude, const char* longitude, const char* lat_direction,
                   const char* lon_direction, char* lat_return, char* lon_return, int buff_length)
  char lat_deg[3];

  // extract the first 2 chars to get the latitudinal degrees
  strncpy(lat_deg, latitude, 2);

  // null terminate
  lat_deg[2] = 0;

  char lon_deg[4];

  // extract first 3 chars to get the longitudinal degrees
  strncpy(lon_deg, longitude, 3);

  // null terminate
  lon_deg[3] = 0;

  // convert to integer from char array
  int lat_deg_int = arrayToInt(lat_deg);
  int lon_deg_int = arrayToInt(lon_deg);

  // must now take remainder/60
  // this is to convert from degrees-mins-secs to decimal degrees
  // so the coordinates are "google mappable"

  // convert the entire degrees-mins-secs coordinates into a float - this is for easier manipulation later
  float latitude_float = arrayToFloat(latitude);
  float longitude_float = arrayToFloat(longitude);

  // remove the degrees part of the coordinates - so we are left with only minutes-seconds part of the coordinates
  latitude_float = latitude_float - (lat_deg_int * 100);
  longitude_float = longitude_float - (lon_deg_int * 100);

  // convert minutes-seconds to decimal
  latitude_float /= 60;
  longitude_float /= 60;

  // add back on the degrees part, so it is decimal degrees
  latitude_float += lat_deg_int;
  longitude_float += lon_deg_int;

  if (strcmp (lat_direction, "S") == 0) {
    latitude_float *= -1;

  if (strcmp (lon_direction, "W") == 0) {
    longitude_float *= -1;

  // format the coordinates nicey - no more than 6 decimal places
  snprintf(lat_return, buff_length, "%2.6f", latitude_float);
  snprintf(lon_return, buff_length, "%3.6f", longitude_float);

int arrayToInt(const char* char_array)
  int temp;
  sscanf(char_array, "%d", &temp);
  return temp;

float arrayToFloat(const char* char_array)
  float temp;
  sscanf(char_array, "%f", &temp);
  return temp;

const char *nextToken(const char* src, char* buf)
  int i = 0;
  while (src[i] != 0 && src[i] != ',')
  if (buf)
    strncpy(buf, src, i);
    buf[i] = 0;
  if (src[i])
  return src + i;

boolean wifi_status(LWifiStatus ws) {
  switch (ws) {
      return false;
      return false;
      return true;
  return false;

Connect your LinkIt One device via USB cable and select Serial Debug COM port in Arduino IDE. Compile and Upload your sketch to device using “Upload” button.

After application will be uploaded and started it will try to connect to Thingsboard node using mqtt client and upload “latitude” and “longitude” attributes once per second.


When application is running you can connect your device to Serial Debug COM port in Arduino IDE and open “Serial Monitor” in order to view debug information produced by serial output.

Data visualization

Finally, open Thingsboard Web UI. You can access this dashboard by logging in as a tenant administrator. Use

in case of local Thingsboard installation.

Go to “Devices” section and locate “LinkIt One Demo Device”, open device details and switch to “Attributes” tab. If all is configured correctly you should be able to see “latitude”, “longitude” and battery status attributes and theirs latest values in the table.


After, open “Dashboards” section then locate and open “LinkIt One GPS Tracking Demo Dashboard”. As a result you will see the map widget with pointer indicating your device location and battery level widget (similar to dashboard image in the introduction).

Next steps

Browse other samples or explore guides related to main Thingsboard features:

Your feedback

If you found this article interesting, please leave your feedback in the comments section, post questions or feature requests on the forum and “star” our project on the github in order to stay tuned for new releases and tutorials.


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