Sound Playback/Compression System [M3S-S2-Tiny] for RL78 Family


Sound playback system

M3S-S2-Tiny (hereafter abbreviated S2) is the sound playback system which just requires small memory.

We have the various lineup of MCUs, including RX Family, which are suitable for use in applications such as single-function home appliances and compact industrial equipment, where the incorporation of more sophisticated functionality or the newest technology, with a negligible increase in cost, is desired. To support such development activities, Renesas offers software libraries with only the essential features for application, at low cost.

Use S2 to enable sound output in any device incorporating a target microcontroller. S2's original algorithm compresses and expands sound in ADPCM mode compactly at high speed. It can be used to add true sound output functionality to devices that previously only provided visual indications or beeps.


  • Sound compression and expansion using Renesas-specific ADPCM format
    16-bit PCM data (files in wav format) is compressed to 4-bit quantity on your PC, and the compressed 4-bit data is expanded to 16-bit PCM data on microcontroller. Then expanded 16-bit data is converted to 8- or 10-bit data according to your system's requirements.
  • The compressed data of two or more sound channels can be expanded in parallel.
  • The processing of expansion being optimized MCU by MCU, the revised product can expand decompressed data 30% faster than the previous one.
    e.g. MCUs of the R8C Family running at 4 MHz are capable of expanding (reproducing) sound data that has been sampled at a frequency of 8 kHz.
  • Compact design tailored for embedded systems
    Realizable using the internal memory of the MCUs: Approx. 0.4-Kbyte ROM and approx. 20-byte RAM (for the R8C Family case) *including the stack
  • Includes sound compression/expansion utility (PC application) Recorded sound data (in wav format) can be compressed on a PC. (The compressed data can be incorporated into the microcontroller.)

    * The compressible formats are 16 bits quantized monaural PCM (files in wav format).

  • Includes sample programs which responds to Renesas IDE.

Release Information

Target Device Software Name Version/Release Date Status
RL78 Family M3S-S2-Tiny for the RL78 Family Latest Ver.: V.3.01 Release 00
Released: Mar 11, 2015
Sample Code

Details of upgrade (See Tool News)

Operating Environment

* The Application Notes and Sample Code of S2 for the MCUs are available. Please download from here.


  • Sound data expansion software (library in binary format)
  • Sample software for sound reproduction
    (Source file in CS+ format, e2 studio format project files and High-performance Embedded Workshop format workspace that includes a sample driver for PWM output)
  • Library function and sample software user's manual and other documents in a complete set
  • Sound data compression/expansion tool (PC software)

Modular Composition

For sound decompression

For Sound Decompression

For sound compression

For Sound Compression

Operating Environment

Target Device RL78 Family
Supported Evaluation Environment CS+
IAR Embedded Workbench for RL78 family provided by IAR Systems
Occupied ROM Size Approx. 0.8Kbytes
Occupied RAM Size For sound decompression: approx. 40bytes
For sound compression: approx. 30bytes

* Including the stack


  • Sound guidance
    • Salutations such as “Welcome” and “Thank you”
    • Guidance for equipment operation procedures such as “Please follow instructions” and “Please call the attendant”
    • Announcements such as “The bath is ready” and “Breakfast is ready”
    • Repeated playback of simple commercial or advertisement such as “Put on the market today”
  • Security
    • A trespasser, when detected, is warned by a large sound. “Informed to police” or “Crime-prevention camera is at work”
  • Safety measures
    • Calling one’s attention for safety. “Hot water will run out” or “The door will be closed”
    • Warning one about abnormal state: “The door (lid) is open” or “The pot has run out of water”

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