Temperature Web Panel

This example shows how to serve data from an analog input via the Arduino Yún's built-in webserver using the Bridge library.

Prepare your SD card with an empty folder in the SD root named "arduino" and a subfolder of that named "www". This will ensure that the Yún will create a link to the SD to the "/mnt/sd" path.

In this sketch folder is a basic webpage and a copy of zepto.js, a minimized version of jQuery. When you upload your sketch, these files will be placed in the /arduino/www/TemperatureWebPanel folder on your SD card.

You can then go to http://arduino.local/sd/TemperatureWebPanel to see the output of this sketch.

You can remove the SD card while the Linux and the sketch are running but be careful not to remove it while the system is writing to it.

Hardware Required

  • Arduino Yún
  • computer and Yún on the same wireless or wired network
  • TMP36 temperature sensor on analog pin A1
  • SD card attached to SD card slot of the Arduino Yún
  • hook-up wies
  • breadboard


Attach a TMP36 temperature sensor on A1, and insert a micro-SD card into the slot on the Yún.

image developed using Fritzing. For more circuit examples, see the Fritzing project page


image developed using Fritzing. For more circuit examples, see the Fritzing project page


You need to include the Bridge, YunServer, and YunClient libraries :

#include <Bridge.h>
#include <YunServer.h>
#include <YunClient.h>

Instantiate a server enabling the the Yún to listen for connected clients.

YunServer server;

Create a string to hold the time the sketch started, and a variable to keep track of the number of times the page has been visited.

String startString;
long hits = 0;

In setup() , start serial communication and Bridge. It's helpful to use the on-board LED as a status light to know when Bridge has started.

void setup() {

  digitalWrite(13, LOW);
  digitalWrite(13, HIGH);

Set A0 and A2 as power and ground for the TMP36 sensor (this helps avoid using a breadboard).

pinMode(A0, OUTPUT);
  pinMode(A2, OUTPUT);
  digitalWrite(A0, HIGH);
  digitalWrite(A2, LOW);

Tell the server to listen for incoming connections only from localhost and start it


Create an instance of Process to get the time the sketch started by running the date command and storing it in the string you created earlier.

Process startTime;
  while(startTime.available()) {
    char c = startTime.read();
    startString += c;

In loop(), create a named instance of YunClient to get any clients coming from the server.

YunClient client = server.accept();

If there is a new client connected, read the command the client sent and print it out.

if (client) {
    String command = client.readString();
    command.trim();        //kill whitespace

If the command is "temperature", get the current time and read the value of the temperature sensor.

if (command == "temperature") {

      Process time;
      String timeString = "";
      while(time.available()) {
        char c = time.read();
        timeString += c;
      int sensorValue = analogRead(A1);

Convert the sensor's reading to temperature Celsius :

// convert the reading to millivolts:
      float voltage = sensorValue *  (5000/ 1024);
      // convert the millivolts to temperature celsius:
      float temperature = (voltage - 500)/10;

Print the current time, temperature, time the sketch was started, and the number of hits since starting to the connected client with client.print().

client.print("Current time on the Yun: ");
      client.print("<br>Current temperature: ");
      client.print(" degrees C");
      client.print("<br>This sketch has been running since ");
      client.print("<br>Hits so far: ");

Close the connection to free up any unused resources and increment the hit counter.


Pause for a few moments before polling anew

delay(50); // Poll every 50ms

The complete code is below :

SORRY, There is an error at our code repository, please inform to web@arduino.cc

See Also

  • Bridge Library - Your reference to the Bridge Library
  • Bridge – Simple REST style calls to access analog and digital pins
  • Consolle Ascii Table – A complete ASCII table printed to the Console
  • Console Pixel – Turn an LED on and off through the Console
  • Console Read - Read data coming from bridge using the Console.read() function
  • Data Logger - Log data from three analog sensors to an SD card.
  • File Write - How to write file into the Yún filesystem.
  • Http Client - A basic HTTP client that connects to the internet and downloads content.
  • Mailbox Read Message - How to read the messages queue, called Mailbox, using the Bridge library.
  • Process - How to run linux processes using an Arduino Yún.
  • Shell Commands - How to run linux shell commands using an Arduino Yún.
  • Time check - Gets the time from Linux via Bridge then parses out hours, minutes and seconds.
  • WiFi Status - Prints information about the status of your wifi connection.
  • Serial Terminal - Use the Yún's 32U4 processor as a serial terminal for the Linux side on the Yún.

Last revision 2015/08/12 by SM