🛠 Connexion Wi-Fi 5 GHz et pilotage en SSH

Objectives

Configure the board as a Wi-Fi station (dual-band 2.4/5 GHz chip), understand the regulatory lock that hides 5 GHz channels until the country is set, start headless (without a screen), and control the board via SSH from another computer. Expected throughput in 5 GHz: approximately 100 Mb/s versus 47 Mb/s in 2.4 GHz.

Hardware

• Raspberry Pi 3 Model B+ type board (integrated dual-band 802.11ac Wi-Fi)
• Box/router with a 5 GHz network
• Another computer for SSH; or a screen + keyboard for the initial configuration
• 5.1 V 2.5 A power supply

Complete code

# 1. Définir le domaine réglementaire AVANT de chercher les réseaux 5 GHz
sudo raspi-config nonint do_wifi_country FR

# 2. Activer le client Wi-Fi (wpa_supplicant) et le SSH
sudo raspi-config nonint do_ssh 0

# 3. Se connecter au point d'accès (remplacer SSID et cle)
sudo tee /etc/wpa_supplicant/conf.d/01-wlan.conf >/dev/null <<'EOF'
network={
    ssid="MON_SSID_5GHZ"
    ps1="MA_CLE_WIFI"
}
EOF
sudo wpa_cli -i wlan0 reconfigure

# 4. Obtenir une adresse IP et vérifier
sudo dhclient wlan0
ip -4 addr show wlan0
iwgetid -r          # affiche le SSID associé

# 5. Depuis un autre poste : ssh pi@<adresse-ip>

Expected verification

iwgetid -r displays the SSID, ping -c3 1.1.1.1 reaches the Internet, and from the other computer ssh pi@board-ip opens a shell. iw dev wlan0 info shows a 5 GHz channel (number ≥ 36) once the country FR is set. Without country=FR, 5 GHz networks appear "not found".

Common errors

• Country not set: regulations (cfg80211) hide 5 GHz channels — this is the #1 pitfall on the 3B+.
• Wi-Fi key with spaces or unescaped special characters in the config file.
• Metal case: the printed antenna needs clearance; shielding kills both bands.
• Weak power supply: Wi-Fi transmission slots trigger voltage drops below 4.63 V and disconnections.
• Two network managers conflicting (dhcpcd + NetworkManager): keep only one.
• DHCP expired after router sleep: sudo dhclient -r wlan0 && sudo dhclient wlan0.