access_point_wifi_provisioning

Access point Wi-Fi provisioning

This example shows how to provision Wi-Fi credentials over an access point, so a headless Pico W can be put onto a network without compiling the SSID and password into the firmware. Credentials entered through a web page are saved to flash and reused on subsequent boots, so once a network has been provisioned the device connects to it automatically.

How it works

On startup the Pico W reads any credentials saved in flash and tries each set in turn as a Wi-Fi station (STA). If one succeeds, provisioning is complete and the example goes on to run an iperf server as a placeholder for whatever your application would do once connected.

If no saved credentials work (or none are stored yet), the Pico W starts an access point named picow_test and runs a web server on it. Connect a phone or laptop to that access point and you will be directed to a provisioning page where you can enter the SSID and password of the network you want to join. A bundled DNS server resolves every name to the Pico W itself, so any address you open in a browser lands on the provisioning page (a captive portal). A DHCP server hands the connecting device an address on the access point's subnet.

When you submit credentials the Pico W attempts to join that network. The access point stays up during the attempt, so the page remains reachable: if the join fails you can simply try again without reconnecting. On success the access point and its DNS/DHCP servers are shut down and the new credentials are saved to flash for next time.

You can also pick from previously saved networks on the same page, and clear all saved credentials with the "Clear saved credentials" button.

Using it

1. Build and flash the example, then open a serial terminal to watch its progress.
2. On first run there are no saved credentials, so the Pico W starts the picow_test access point (password password).
3. Connect a phone or laptop to picow_test. Most devices will pop up the captive-portal page automatically; if not, open any web address in a browser.
4. Enter the SSID and password of your network and press Connect.
5. On success the Pico W joins your network, shuts down the access point, and saves the credentials. The serial output shows the assigned IP address.
6. On later boots the Pico W connects to a saved network automatically without starting the access point.

At startup the example also offers two serial options: press w within the first few seconds to wipe all stored credentials, or s to skip the automatic connect and go straight to the access point.

Notes

Credentials are stored in a single flash sector as a list of SSID/password pairs. Saving a network whose SSID already exists updates that entry in place rather than adding a duplicate. The number of stored networks and the maximum SSID/password lengths are set by MAX_CREDENTIALS, MAX_SSID_LEN and MAX_PASSWORD_LEN in the source; the list must fit within one 4096-byte sector.