This paper presents a functional reactive embedded domain-specific language (EDSL) for resource-constrained embedded systems and its efficient execution method. In the language, time-varying values changes at discrete points of time rather than continuously. Combined with a mechanism to let users designate the update interval of values, it is possible to derive the minimal value-updates required to produce the user-desired output. Also, the event-driven backend asynchronously updates an input value when its value is required. In this way, we can greatly reduce the number of updates.