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EPSON – S1C31D51: 32-bit Arm® Cortex®- M0+ flash microcontroller for voice output and audio playback via loudspeaker or buzzer

In modern home electronics such as household appliances, remote controls of all kinds in the smart home sector, in toys, in health and fitness equipment, in many industrial applications such as building automation or as an alarm function, voice output and audio playback functions are becoming increasingly more popular. This makes the equipment easier to use, more understandable and sometimes even luxurious.


The 32-bit MCU, based on the Arm® Cortex®-M0+ processor with integrated hardware processor for audio playback, is a single chip microcontroller. Voice output and audio playback can be mixed and supported simultaneously via two separate output channels. In addition, the voice output can also be realized on the S1C31D51 via a buzzer and not only via loudspeakers. And it can be done simply by specifying the sentence number from the CPU (see the diagram of S1C31D50/51).





The S1C31D51 offers voice output and audio playback function for a wide range of products.

Conventional buzzers are often very underpowered due to low volume and limited audio bandwidth. Epson has therefore improved the performance of the buzzer through a combination of PC software and hardware support. With this buzzer solution, Epson has a unique selling point in the market to realize an unexpected audio quality even on a low power or low budget system solution.

Special product features S1C31D51:

  • A variety of options for sound reproduction
    • Electromagnetic or piezoelectric buzzer
    • Loudspeaker
  • The integrated hardware processor performs a variety of functions without using CPU resources
    • Playback both background music and speech with sampling rate of 15.625 kHz is sufficiently high
    • Changing the speech rate in 5% steps within a range of 75% to 125 %, keeping the same pitch
    • Independent volume control for each channel
    • Memory self-check function (RAM, internal Flash, external QSPI Flash)
  • Easy creation of voice data with Epson’s PC tool Voice Creation (ESPER 2)

In applications where speech output is implemented, a large part of the overall development afford is not the hardware design, but the creation of the required audio recordings and their necessary post-processing to achieve a homogeneous auditory impression.

With the ESPER2 Voice Data Creation PC Tool, which is provided free of charge, voice and audio files can be generated easily. With a text 2 speech engine words, phrases and sentences can be generated directly with Epson’s very effective codec.

The quality of the data is so high, that no time-consuming and costly studio booking and recording is necessary. The ESPER 2 tool currently supports 12 different languages. Existing audio files in WAV format can also be easily imported into the tool.

Facts about the PC tool ESPER 2:

  • Guided process of speech data production in four steps
  • Fine-tuning of pronunciation possible
  • Only 120kB/min with 16bit sampling
  • Save playback memory . The same phrases are common to minimize the data.
  • Sound data is generated not only as binary, but also as code that can be imported directly into the development environment.
  • Evaluation board available for direct development

If we were able to convince you with the Epson MCU solution for audio playback and speech output, we will be happy to prepare an offer for your application. Ask us for a demonstration of the audio workflow and the output quality of Epson´s S1C31D51 driven design. Contact us!

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