In this work, we propose a complete methodology called RESS (Real-Time Embedded Software Synthesis) for the automatic design of real-time embedded software. Several issues are solved, including software synthesis, software verification, code generation, graphic user interface, and system emulation. To avoid design errors, a formal approach is adopted because glitches in real-time embedded software are intolerable and very expensive or even impossible to fix. Time Complex-choice Petri Nets are used to model real-time embedded software, which are then synthesized using a time extended quasi static scheduling algorithm. The final generated C code is prototyped on an emulation platform, which consists of an 89C51 microcontroller for executing the software, an FPGA chip for programming the hardware for different applications, and some input/output devices. Two application examples are used to illustrate the feasibility of the RESS methodology.