The FOTA module handles polling, downloading, and applying firmware images. Main subscribes to fota_chan and coordinates what happens around those steps while in STATE_FOTA.
When the FOTA module begins a download, it publishes FOTA_STARTING. Main responds by entering STATE_FOTA and shows a purple LED pattern for the duration of the download.
Before the device can reboot or apply a full modem image, the FOTA module may need LTE offline. It then publishes FOTA_NETWORK_DISCONNECT_NEEDED. Main disconnects via network_chan and, once the network is down, replies with FOTA_NETWORK_DISCONNECTED so the FOTA module can continue.
When the update is ready to take effect, the FOTA module publishes FOTA_REQUEST_REBOOT. Main clears buffered sample data by publishing STORAGE_CLEAR on storage_chan, then transitions to STATE_REBOOTING. Wiping storage before reboot avoids carrying stale or incompatible data into the new firmware.
If the update fails or is cancelled, the FOTA module publishes FOTA_ABORTED and Main returns to the state it was in before the download started.
For operator steps, see Firmware updates (FOTA).