Our Framework (frw) proposes to separate concerns in IoT devices in a new way, offering upgradeability by default. We explain the design of the frw, and demonstrate a full-stack implementation. Typical IoT appliances integrate physical and network capabilities inseparably. Therefore, when either fails or becomes obsolete, the whole appliance turns useless. This is a major source of consumer inconvenience, and has severe environmental impacts. Our design splits functionalities in IoT appliances differently: Digital control is mediated through the simple, self-describing SerIoT (siot) interface whose protocol draws on the Web of Things recommendation's Thing Description (TD) and JSON. Different Clients (clients) such as network adapters have this one single interface to attach to, on every compatible appliance, and are replaceable whenever the network-facing connectivity technology changes. Our practical demonstrator leverages an existing device abstraction codebase for an IoT-retrofit espresso maker, connects it to the proposed siot interface, and then bridges it to a Home Assistant instance over WLAN by means of a network adapter that accesses the siot interface.