A speech synthesis technology based on PWM which is capable of rewriting online

In order to solve the problem that special audio chip cannot rewrite Speech content online, a low-cost technological scheme is proposed in this paper. It adopts Pulse Width Modulation (PWM) technology and microcontrollers with PWM peripherals to turn WAV file date into Pulse Width Modulation wave and to recover analog speech signal through low-pass filter. By using the RS485 bus to rewrite WAV file in the Flash-ROM, this scheme achieves the goal of rewriting speech content online. In this paper, the Fourier series of PWM signal and the low pass filter are simulated and analyzed, which provides reference for the design of PWM-A/D converter's low-pass filter.