It is possible to assign device by ACS identifier (Barcode or Serial number) to customer before device establishes first connection to ACS. Splynx checks for some value in a field Barcode of inventory item. If Barcode, on the first connection, matches with Serial number device field, customer will be linked automatically. If field Barcode is empty or does not match Serial number of a device, in this case, field Serial number will be used from inventory item. This way you can add an inventory item with a barcode or serial number specified and assign it to a customer:

After this, you can setup some group and auto provisioning. For example to push PPPoE login & password, WI_FI SSID & password on first connect. During the first connection, a TR-069 device will be automatically assigned to a customer and an initial configuration will be pushed (Config → Networking → TR-069 (ACS) Groups → Edit group):

And after the first connect:

The customer can reboot the router and change SSID and Wi-Fi password for assigned devices directly from portal page on menu Services → Hardware: