This paper reports the implementation of Emfrp-REPL, an interactive interpreter (REPL) of a functional reactive programming (FRP) language for resource-constrained embedded systems. Its goal is to accelerate the prototyping and development of microcontroller-based embedded systems. The interpreter runs on small-scale embedded devices based on 32-bit microcontrollers, such as ESP32 with 520KiB size data RAM. The evaluation shows that the memory usage of Emfrp-REPL is comparable to MicroPython, and the range of its latency is narrower than MicroPython, according to microbenchmarks.