> For the complete documentation index, see [llms.txt](https://amobile-solutions.gitbook.io/yocto-developer-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://amobile-solutions.gitbook.io/yocto-developer-guide/test-and-use-the-interface/wi-fi/wi-fi-iot-800n-g420.md). # Wi-Fi - IOT-800N-G420 ## Overview | | | | ----------------- | ---------------------------- | | Module | MediaTek MT7921S, on the SoM | | Standards | 802.11 a/b/g/n/ac/ax, 2T2R | | Interface | **SDIO** (`mmc2`), not PCIe | | Driver | `mt76` (`mt7921s`) | | Network interface | `wlan0` | WiFi and Bluetooth are two SDIO functions of the same chip, so if `mmc2` does not come up neither appears. ## Checking the interface ``` ip link show wlan0 iw dev ``` ``` dmesg | grep -i mt7921 ``` Firmware loading should be visible: ``` mt7921s ...: WM Firmware Version: ____, Build Time: ... ``` The required firmware comes from `linux-firmware`: ``` ls /lib/firmware/mediatek/WIFI_RAM_CODE_MT7961* ls /lib/firmware/mediatek/WIFI_MT7961* ``` ## Scanning ``` nmcli dev wifi list ``` or ``` iw dev wlan0 scan | grep SSID ``` ## Connecting with NetworkManager ### Enabling and disabling ``` nmcli radio wifi on nmcli radio wifi off ``` To check the state: ``` nmcli dev show wlan0 ``` `GENERAL.STATE` reads `connected` or `disconnected` when WiFi is enabled, and `unavailable` when it is not. ### Open network ``` nmcli dev wifi connect ifname wlan0 ``` Hidden: ``` nmcli dev wifi connect hidden yes ifname wlan0 ``` ### Protected network ``` nmcli dev wifi connect password ifname wlan0 ``` Hidden: ``` nmcli dev wifi connect password hidden yes ifname wlan0 ``` ### Managing connections Connections persist across reboots unless deleted. ``` nmcli con show nmcli con down nmcli con up nmcli con delete ``` ## Access point mode NetworkManager can turn the interface into an AP, handling the DHCP server and NAT configuration at the same time. ### Disable the standalone dnsmasq ``` systemctl disable dnsmasq systemctl stop dnsmasq ``` Then in `/etc/NetworkManager/NetworkManager.conf`: ``` [main] dns=dnsmasq [ifupdown] managed=false ``` ### Create the AP ``` nmcli con add type wifi ifname wlan0 mode ap con-name WIFI_AP ssid MY_AP && \ nmcli con modify WIFI_AP 802-11-wireless.band bg && \ nmcli con modify WIFI_AP 802-11-wireless.channel 1 && \ nmcli con modify WIFI_AP 802-11-wireless-security.key-mgmt wpa-psk && \ nmcli con modify WIFI_AP 802-11-wireless-security.proto rsn && \ nmcli con modify WIFI_AP 802-11-wireless-security.group ccmp && \ nmcli con modify WIFI_AP 802-11-wireless-security.pairwise ccmp && \ nmcli con modify WIFI_AP 802-11-wireless-security.psk 11223344 && \ nmcli con modify WIFI_AP ipv4.method shared && \ nmcli con up WIFI_AP ``` For the 5 GHz band: ``` nmcli con modify WIFI_AP 802-11-wireless.band a nmcli con modify WIFI_AP 802-11-wireless.channel 36 ``` ### DHCP subnet The default is 10.42.0.x/24 with the AP at 10.42.0.1. ``` nmcli con modify WIFI_AP ipv4.addr 192.168.5.1/24 ``` ## Troubleshooting ### wlan0 does not appear The MT7921 needs the PMIC's `vcn18` rail, which supplies the IO side of the SDIO bus. ``` grep vcn18 /sys/kernel/debug/regulator/regulator_summary ``` A use count of 0 means the rail is not enabled, and the chip will never answer CMD5: ``` dmesg | grep mmc2 ``` ``` mmc2: error -110 whilst initialising SDIO card ``` {% hint style="warning" %} Unbinding and rebinding the driver does not help here — rebinding does not make a missing supply appear. The rail has to be enabled in the device tree. {% endhint %} ### The MAC address looks wrong The MAC is programmed during production. An address beginning `02:` or one that changes between boots means the driver generated a random one because it could not read the programmed value. ``` ip link show wlan0 | grep ether ```