It is now common sense that various embedded devices are connected to the network. What kind of things should be considered in order to achieve IoT that connects embedded devices that used to operate as standalone devices to networks and connects to smartphones and the cloud? Regarding the necessary components (edge device / gateway / cloud / application) for the IoT system, we will explain considerations and important points from the point of view of implementation. In addition, based on specific cases, we will talk about the key points for converting embedded devices to IoT.