🛠 Connecter la Yún au WiFi et piloter une broche depuis le navigateur

Objectives

Leverage the Yún's networking capabilities: connect to its "Arduino Yun" WiFi access point (restore mode), access the built-in configuration page, join your home network, and control a digital pin directly via a URL — without writing a single line of code, thanks to the REST API embedded in Linino OS.

Hardware

• 1 Arduino Yún + 5 V USB power supply (or 7–12 V jack)
• A PC/smartphone connected to the same network as the board
• 1 LED + 330 Ω resistor on pin 13 (or the built-in "L" LED)
• Optionally, an Ethernet cable for initial troubleshooting if WiFi fails

Complete Procedure

1. Power on the Yún. For approximately 20 seconds during startup, it broadcasts an open WiFi network named Arduino Yun (restore mode). Connect to it (password: WiFi is open on first boot, then protected by the default admin password "yun" — depending on the Linino OS version).
2. Open http://arduino.local (or the IP address displayed on the captive portal page). The configuration panel asks for the root password (default: yun).
3. In the WiFi configuration tab: select your network, enter the key, and confirm. The board restarts and joins your access point.
4. Test the REST API directly in your browser (pin 13 set as output):

# Mettre la pin 13 en sortie, niveau HIGH :
http://arduino.local/arduino/digital/13/1

# Niveau LOW :
http://arduino.local/arduino/digital/13/0

# Lecture d'une broche numérique (réponse texte) :
http://arduino.local/arduino/digital/7

These routes work WITHOUT a specific sketch on the 32U4: the Bridge service on the Linux side drives the pins directly, provided that a sketch with Bridge.begin (or the BridgeYunServer example sketch) keeps the bridge alive. This is the quickest way to verify that the 32U4 ↔ AR9331 duo is communicating (they talk via the internal serial port, pins 0/1 of the 32U4).

Expected Verification

http://arduino.local responds → Linux is online and reachable. The command /arduino/digital/13/1 turns the LED on instantly; /13/0 turns it off. From a terminal: curl http://arduino.local/arduino/digital/13/1 does the same thing. If arduino.local does not respond (mDNS resolution can be flaky on Windows), use the IP address displayed on the configuration page.

Common Errors

• Missing the first 20-second window: the "Arduino Yun" network only appears at startup (or after holding the WiFi button for a long time — hold it for ~30 seconds to force restore mode).
• Forgetting that a sketch must keep the Bridge alive: the /arduino/* routes require the Bridge service to be active on the 32U4; upload at least the BridgeYunServer example sketch.
• Root password changed and then forgotten: the WiFi restore button does NOT reset the root password — you must then reinstall Linino OS (see the advanced recovery tutorial).
• Two Yún boards on the same network: arduino.local causes a collision (mDNS); name them or use their IP addresses.
• WiFi is limited to 2.4 GHz 802.11 b/g/n (AR9331 radio): pure 5 GHz networks are invisible.