ARM MCU plays voice over a buzzer

ARM MCU plays voice over a buzzer

By Nick Flaherty

Seiko Epson has developed a microcontroller (MCU) than can play voice samples on a low cost buzzer

The S1C31D51 a 32bit 16MHz ARM Cortex-M0+ controller with dedicated hardware which can play sound on either a speaker or buzzer. Epson plans to produce 200,000 of the new controllers per month.

By making it possible to output voice guidance sound like error and warning messages on a buzzer instead of a speaker drives sound interfaces into more home electronics designs, remote controllers for home appliances, industrial devices, health and fitness equipment with guidance systems and alarms in office buildings, shopping complexes, and factories.

This is possible through a combination of dual channel dedicated hardware and software running on the Cortex-M0+ core without needing the central processor (CPU). The use of a high data compression algorithm that delivers 16 kbps data rates at 15.625 kHz shrinks the size of sound data memory, making it possible to provide a large amount of sound data and sound data in multiple languages. The compression runs up to 40kbps.

The two channel processing and higher bandwidth allows music and voice to be played over a speaker.

Epson has also developed a free Voice Creation development tool without the need for a studio recording. This PC-based tool is a simple development environment for easily creating sound data for 12 languages without studio recording and accessed directly via the MCU registers. Developers can also use existing WAV data.

The chip supports British English, German, French, Spanish, Italian and Russian as well as American English, American Spanish and Canadian French with Japanese, Chinese and Korean

The MCU also has a self- memory check function that can detect failures in built-in RAM, built-in flash memory or the external QSPI-Flash memories, again without using CPU resources.

An evaluation board for the S1C31D51 includes a TDK electromagnetic and piezoelectric buzzer that allows quick audio testing along with the preset demonstration. The sound data is assigned a number in the PC tool and is played back by specifying the assigned number in the MCU register, so there is no need to create and evaluate codes for linking sound data.

Next: S1C31D51 voice video and product specification

Product number


CPU core

CPU core ARM Cortex-M0+ 32-bit RISC processor

Flash memory

192 kB (for both programs and sound data)


10 kB (22 kB when not playing audio)

HW processor

Sound playback (original Epson format, 15.625 kHz sampling rate, 2-channel mixing, voice speed conversion)

Self-memory check function (built-in Flash & RAM, external QSPI-Flash)

Sound DAC

Sampling rate: 15.625 kHz, mono

Serial interfaces

UART, SPI, and I2C: 3 channels each. QSPI: 1 channel

A/D converter

8 inputs, max. (12-bit successive-approximation ADC)

Supply voltage detector

32 level (1.7 V – 4.3 V)


4 channels (memory ⇔ memory, memory ⇔ peripheral)

Resistor to Frequency Converter(RFC)

1-channel, low-resistance sensor A-D conversion, CR oscillation with 24-bit counters

Infrared remote controller

1 channel (can be used to generate EL lamp driving waveforms)


16-bit timer (8 channels), 16-bit PWM (2 channels), watchdog timer (WDT), real-time clock (RTC)

Power supply voltage

Guaranteed operating range: 1.8 V – 5.5 V

SPI-Flash interface voltage

3.3 V (3.0 V – 3.6 V)

Operating frequency

16 MHz (VD1 voltage mode: mode 0)
1.8 MHz (VD1 voltage mode: mode 1)

Power consumption*2

RUN: 243 uA/MHz (VD1 voltage mode: mode 0)
RUN: 155 uA / 1 MHz (VD1 voltage mode: mode 1)
SLEEP: 0.46 uA, RTC mode: 0.95 uA

I/O ports

Max. 91
Of which up to 32 may be universal port multiplexers (UPMUX)


P-TQFP048-0707-0.50 (pin pitch: 0.5 mm)
P-LQFP064-1010-0.50 (pin pitch: 0.5 mm)
P-TQFP080-1212-0.50 (pin pitch: 0.5 mm)
P-LQFP100-1414-0.50 (pin pitch: 0.5 mm)

More details are at

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