Yún First Configuration

This example shows you how to connect to a WiFi network with your Yún device using the Serial Monitor as the communication interface during the whole process.

Upload the sketch on your Yún device and open the Serial Monitor. The Serial Monitor output will display the available WiFi networks, then asks you to choose the one to use. You have to input the network password and then you are asked to give your Yún device a name and a password. If the connection with the selected network is successful, you get a confirmation message and the IP assigned to your Yún device. By pasting this IP address on your web browser you will be able to reach the Yún Panel for further options.

If something goes wrong, you can restart the procedure; if the network you want to connect to is not in the list, you may proceed with the manual selection specifying the network SSID and passkey.

Note: this sketch requires that your Yún device is running on firmware version 1.6.2 or newer. Please check the upgrade tutorial and be sure you're running the latest version available.

Hardware Required

  • Yún board or shield
  • a wireless network connected to the internet


There is no circuit for this example.

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

Software Essentials


Process.h is used to launch processes on the Linux processor, and other things like shell scripts. Here we use it to get the list of APs and to perform other actions that let us know the WiFi parameters.


String getUserInput(String out, bool obfuscated) – manages the input from the user through the Serial Monitor, printing back in the window. The boolean variable “obfuscated” is used to print out “*” when a password is entered.

void wifiConfig(String yunName, String yunPsw, String wifissid, String wifipsw, String wifiAPname, String countryCode, String encryption) – uses Process to execute a series of commands and scripts, under linux, that set the WiFi and network parameters as chosen by the user.

void startSerialTerminal() – simply initialize the two serial ports needed to perform the actions required by the sketch.

void loopSerialTerminal() – creates the connection between the two serial ports, one talking with the PC using USB, the other talking to the linux processor. It has a command mode that can be invoked typing '~' that shuts down Bridge and allows to set a different communication speed with the Atheros chip.


This sketch uses the Serial Monitor of your Arduino Software (IDE) to interact with you, asking the relevant information for the configuration. The Yún device uses the hardware serial port on pins 0 and 1 to communicate with the board, therefore this sketch requires a second hardware serial port to work properly. Please get ready with SSID (the Access Point name) and the key or passphrase to access the WiFi network. Load the sketch and then open the Serial Monitor clicking on the Magnifier Lens icon on the right of the icon bar. You will see a message as the one in the screenshot below.

The blue LED on the shield will start to blink after a while; when the scanning process is over, the sketch will offer all the available APs in a numbered list. The time required to scan the network depends on the number of APs and their signal strength. You choose the AP to use typing in the input field the corresponding number. Please remember to enable “NL” in the Serial Monitor as End of Line.

The selection of the AP triggers the connection process and the Yún device will sense if the network is open or protected. In this later case, you will be asked to provide the key. The Yún device needs to be named and protected with a password to allow easy and secure connections. Following these step, your device is ready to connect to the WiFi network, switching off the AP mode and initiating the access to the selected WiFi network. At the end of this process, the sketch will show the IP address obtained from the WiFi DHCP server.

If the connection fails, the sketch will report it and suggest to restart the whole procedure with a reset of your Yún device.


The complete sketch is below :

  Arduino Yún First configuration sketch

  Configures the YunShield/Yún WiFi and infos via the Bridge
  Works correctly if Line Ending is set as "NewLine"
  If your board has two USB ports, use the Native one

  The circuit:
   Arduino YunShield
   (or any Yun model with firmware > 1.6.1)

  created March 2016
  by Arduino LLC

  This example code is in the public domain.


#include <Process.h>

#define MAX_WIFI_LIST 10

String networks[MAX_WIFI_LIST];
String yunName;
String yunPassword;

void setup() {
  SERIAL_PORT_USBVIRTUAL.begin(9600);  // initialize serial communication
  while (!SERIAL_PORT_USBVIRTUAL);     // do nothing until the serial monitor is opened

  SERIAL_PORT_USBVIRTUAL.println(F("Hi! Nice to see you!"));
  SERIAL_PORT_USBVIRTUAL.println(F("I'm your Yun assistant sketch"));
  SERIAL_PORT_USBVIRTUAL.println(F("I'll help you configuring your Yun in a matter of minutes"));

  SERIAL_PORT_USBVIRTUAL.println(F("Let's start by communicating with the Linux processor"));
  SERIAL_PORT_USBVIRTUAL.println(F("When LED (L13) will light up we'll be ready to go!"));
  SERIAL_PORT_USBVIRTUAL.println(F("(in the meanwhile, if you are using the IDE's serial monitor, make sure that it's configured to send a \"Newline\")\n"));
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
  Bridge.begin();  // make contact with the linux processor
  digitalWrite(13, HIGH);  // Led on pin 13 turns on when the bridge is ready

  // Recover if the board is in AP mode - unused
  Process wifiList;
  bool master = false;
  wifiList.runShellCommand(F("iwinfo | grep \"Mode: Master\""));
  while (wifiList.available() > 0) {
    master = true;

  // Get the list of reachable networks
  wifiList.runShellCommand(F("iwinfo wlan0 scan | grep ESSID | cut -d\"\\\"\" -f2"));

  uint8_t num_networks = 0;
  uint8_t i = 0;
  char c;
  bool dropNet = false;


  while (wifiList.available() > 0 && i < MAX_WIFI_LIST) {
    c = wifiList.read();
    if (c != '\n') {
      networks[i] += c;
    } else {
      // check if we already found networks[i] and eventually drop it
      for (uint8_t s = 0; s < i; s++) {
        if (networks[i].equals(networks[s])) {
          dropNet = true;
      if (networks[i].c_str()[0] == ' ') {
        dropNet = true;
      if (i < MAX_WIFI_LIST && dropNet == false) {
      } else {
        dropNet = false;
        networks[i] = "";

  num_networks = i;

  String encryption;
  String password;
  int chose = 0;

  // If networks number is 0, start manual configuration
  if (num_networks == 0) {
    SERIAL_PORT_USBVIRTUAL.println(F("Oops, it seems that you have no WiFi network available"));
    SERIAL_PORT_USBVIRTUAL.println(F("Let's configure it manually"));
    SERIAL_PORT_USBVIRTUAL.println(F("SSID of the network you want to connect to: "));
    networks[0] = getUserInput(networks[0], false);
    SERIAL_PORT_USBVIRTUAL.println(F("Password for the network you want to connect to: "));
    password = getUserInput(password, true);
    SERIAL_PORT_USBVIRTUAL.print(F("Encryption (eg WPA, WPA2, WEP): "));
    encryption = getUserInput(encryption, false);
  } else {
    // else print them prepending a number
    SERIAL_PORT_USBVIRTUAL.print(F("It looks like you have "));
    SERIAL_PORT_USBVIRTUAL.println(F(" networks around you "));
    SERIAL_PORT_USBVIRTUAL.println(F("Which one do you want to connect to?\n"));
    for (i = 0; i < num_networks && i < MAX_WIFI_LIST; i++) {
      SERIAL_PORT_USBVIRTUAL.println(") " + networks[i]);
    String selection;
    selection = getUserInput(selection, false);
    chose = atoi(selection.c_str());

  // Extract the selected network security
  bool openNet = false;
  wifiList.runShellCommand("iwinfo wlan0 scan | grep \"" + networks[chose] + "\" -A5 | grep Encryption | cut -f2 -d\":\"");
  while (wifiList.available() > 0) {
    c = wifiList.read();
    encryption += c;

  if (encryption.indexOf("none") >= 0) {
    openNet = true;
    encryption = "none";
  if (encryption.indexOf("WPA2") >= 0) {
    encryption = "psk2";
  if (encryption.indexOf("WPA") >= 0) {
    encryption = "psk";
  if (encryption.indexOf("WEP") >= 0) {
    encryption = "wep";

  if (openNet == false && password.length() == 0) {
    SERIAL_PORT_USBVIRTUAL.print(F("It looks like you need a password to connect to "));
    SERIAL_PORT_USBVIRTUAL.print(F("Write it here: "));
    password = getUserInput(password, true);

  // Change hostname/root password
  SERIAL_PORT_USBVIRTUAL.println(F("We are almost done! Give a name and a password to your Yun"));
  SERIAL_PORT_USBVIRTUAL.print(F("Name: "));
  yunName = getUserInput(yunName, false);
  SERIAL_PORT_USBVIRTUAL.print(F("Password: "));
  yunPassword = getUserInput(yunPassword, true);

  // Select a country code
  String countryCode;
  SERIAL_PORT_USBVIRTUAL.println(F("One last question: where do you live?"));
  SERIAL_PORT_USBVIRTUAL.print(F("Insert a two letters county code (eg IT, US, DE): "));
  countryCode = getUserInput(countryCode, false);


  // Configure the Yun with user provided strings
  wifiConfig(yunName, yunPassword, networks[chose], password, "YUN" + yunName + "AP", countryCode, encryption);

  SERIAL_PORT_USBVIRTUAL.print(F("Waiting for the Yun to connect to the network"));

bool Connected = false;
bool serialTerminalMode = false;
int runs = 0;

void loop() {
  if (!serialTerminalMode) {
    String resultStr = "";

    if (!Connected) {

    // If it takes more than 20 seconds to connect, stop trying
    if (runs > 20) {
      SERIAL_PORT_USBVIRTUAL.println(F("We couldn't connect to the network."));
      SERIAL_PORT_USBVIRTUAL.println(F("Restart the board if you want to execute the wizard again"));
      resultStr = getUserInput(resultStr, false);

    // Check if we have an IP address
    Process wifiCheck;
    wifiCheck.runShellCommand(F("/usr/bin/pretty-wifi-info.lua | grep \"IP address\" | cut -f2 -d\":\" | cut -f1 -d\"/\"" ));  // command you want to run
    while (wifiCheck.available() > 0) {
      char c = wifiCheck.read();
      resultStr += c;


    if (resultStr != "") {
      // We got an IP, freeze the loop, display the value and "spawn" a serial terminal
      Connected = true;
      SERIAL_PORT_USBVIRTUAL.print(F("\nGreat! You can now reach your Yun from a browser typing http://"));
      SERIAL_PORT_USBVIRTUAL.print(F("Press 'Enter' key twice to start a serial terminal"));
      resultStr = getUserInput(resultStr, false);
      serialTerminalMode = true;
      SERIAL_PORT_HARDWARE.write((uint8_t *)"\xff\0\0\x05XXXXX\x7f\xf9", 11); // send "bridge shutdown" command
      SERIAL_PORT_HARDWARE.write((uint8_t *)"\n", 1);
      // discard all stuff for 2 seconds
      long start = millis();
      while (millis() - start < 2000) {
        if (SERIAL_PORT_HARDWARE.available()) {

  } else {

String getUserInput(String out, bool obfuscated) {
    while (SerialUSB.available() <= 0) {}
    while (SerialUSB.available() > 0) {
    char c =  SerialUSB.read();
    out += c;
    return out;

  while (SERIAL_PORT_USBVIRTUAL.available() <= 0) {}
  while (1) {
    char c = SERIAL_PORT_USBVIRTUAL.read();
    char next = SERIAL_PORT_USBVIRTUAL.peek();
    if (c == '\n' || c == '\r') {
      if (next == '\n') {
        // discard it
    else {
      if (c != -1) {
        out += c;
        if (obfuscated)
  return out;

void wifiConfig(String yunName, String yunPsw, String wifissid, String wifipsw, String wifiAPname, String countryCode, String encryption) {
  Process p;

  p.runShellCommand("blink-start 100"); //start the blue blink

  p.runShellCommand("hostname " + yunName); //change the current hostname
  p.runShellCommand("uci set system.@system[0].hostname='" + yunName + "'"); //change teh hostname in uci

  p.runShellCommand("uci set arduino.@arduino[0].access_point_wifi_name='" + wifiAPname + "'");

  //this block resets the wifi psw
  p.runShellCommand("uci set wireless.@wifi-iface[0].encryption='" + encryption + "'");
  p.runShellCommand("uci set wireless.@wifi-iface[0].mode='sta'\n");
  p.runShellCommand("uci set wireless.@wifi-iface[0].ssid='" + wifissid + "'");
  p.runShellCommand("uci set wireless.@wifi-iface[0].key='" + wifipsw + "'");
  p.runShellCommand("uci set wireless.radio0.channel='auto'");
  p.runShellCommand("uci set wireless.radio0.country='" + countryCode + "'");
  p.runShellCommand("uci delete network.lan.ipaddr");
  p.runShellCommand("uci delete network.lan.netmask");
  p.runShellCommand("uci set network.lan.proto='dhcp'");

  p.runShellCommand("echo -e \"" + yunPsw + "\n" + yunPsw + "\" | passwd root"); //change the passwors
  p.runShellCommand("uci commit"); //save the mods done via UCI
  p.runShellCommand("blink-stop"); //start the blue blink

  p.runShellCommand("wifi ");

long linuxBaud = 250000;

void startSerialTerminal() {
  SERIAL_PORT_USBVIRTUAL.begin(115200);  // open serial connection via USB-Serial
  SERIAL_PORT_HARDWARE.begin(linuxBaud); // open serial connection to Linux

boolean commandMode = false;
void loopSerialTerminal() {
  // copy from USB-CDC to UART
  int c = SERIAL_PORT_USBVIRTUAL.read();    // read from USB-CDC
  if (c != -1) {                            // got anything?
    if (commandMode == false) {             // if we aren't in command mode...
      if (c == '~') {                       //    Tilde '~' key pressed?
        commandMode = true;                 //       enter in command mode
      } else {
        SERIAL_PORT_HARDWARE.write(c);      //    otherwise write char to UART
    } else {                                // if we are in command mode...
      if (c == '0') {                       //     '0' key pressed?
        SERIAL_PORT_HARDWARE.begin(57600);  //        set speed to 57600
        SERIAL_PORT_USBVIRTUAL.println("Speed set to 57600");
      } else if (c == '1') {                //     '1' key pressed?
        SERIAL_PORT_HARDWARE.begin(115200); //        set speed to 115200
        SERIAL_PORT_USBVIRTUAL.println("Speed set to 115200");
      } else if (c == '2') {                //     '2' key pressed?
        SERIAL_PORT_HARDWARE.begin(250000); //        set speed to 250000
        SERIAL_PORT_USBVIRTUAL.println("Speed set to 250000");
      } else if (c == '3') {                //     '3' key pressed?
        SERIAL_PORT_HARDWARE.begin(500000); //        set speed to 500000
        SERIAL_PORT_USBVIRTUAL.println("Speed set to 500000");
      } else if (c == '~') {                //     '~` key pressed?
        SERIAL_PORT_HARDWARE.write((uint8_t *)"\xff\0\0\x05XXXXX\x7f\xf9", 11); // send "bridge shutdown" command
        SERIAL_PORT_USBVIRTUAL.println("Sending bridge's shutdown command");
      } else {                              //     any other key pressed?
        SERIAL_PORT_HARDWARE.write('~');    //        write '~' to UART
        SERIAL_PORT_HARDWARE.write(c);      //        write char to UART
      commandMode = false;                  //     in all cases exit from command mode

  // copy from UART to USB-CDC
  c = SERIAL_PORT_HARDWARE.read();          // read from UART
  if (c != -1) {                            // got anything?
    SERIAL_PORT_USBVIRTUAL.write(c);        //    write to USB-CDC

See Also

  • Bridge Library - Your reference to the Bridge Library
  • Bridge – Simple REST style calls to access analog and digital pins
  • Console 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.
  • Http Client Console - HTTP client that connects, downloads content and shows it using WiFi and Console.
  • Mailbox Read Message - How to read the messages queue, called Mailbox, using the Bridge library.
  • Process - How to run linux processes using an Yún.
  • Remote Due Blink - How to upload remotely a sketch on DUE boards.
  • Shell Commands - How to run linux shell commands using a Yún.
  • Temperature Web Panel - How to serve data from an analog input via the Yún's built-in webserver.
  • 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 2016/05/25 by SM