STMicroelectronics STEVAL-MKI138V2

Overview

STEVAL-MKI138V2 from STMicroelectronics is a USB audio interface evaluation board built around the MP34DB01 digital MEMS microphone and STM32F107RC microcontroller, implementing PDM-to-PCM decoding and USB Audio Class 1.0 streaming. It functions as a plug-and-play sound card for PC audio input, supports 1–3.25 MHz PDM sampling, includes on-board LED status indication, and draws power solely via USB.

For engineers reviewing the STEVAL-MKI138V2 datasheet, STEVAL-MKI138V2 pinout, STEVAL-MKI138V2 application, or STEVAL-MKI138V2 equivalent, this page provides verified hardware architecture, USB audio interface timing behavior, PDM input handling capability, and integration guidance for MEMS microphone signal chain development.

Technical Context

The board implements a real-time PDM-to-PCM decimation filter in the STM32F107RC's firmware, supporting stereo input from two MP34DB01 microphones with configurable oversampling ratios. The USB interface operates in full-speed mode (12 Mbps) using CDC ACM and Audio Class 1.0 descriptors to enable OS-level recognition without custom drivers.

Power is delivered exclusively through the USB Type-A connector (5 V), regulating locally to 3.3 V for the microcontroller and microphone bias. Clocking relies on the STM32's internal 8 MHz RC oscillator plus external 25 MHz crystal for USB timing compliance and PDM clock generation.

Key Specifications

Availability

STEVAL-MKI138V2 is available at Aetrix Electronics and suitable for MEMS microphone evaluation, USB audio subsystem prototyping, and embedded voice interface development requiring stable component supply and documented reference firmware.

Supply support for STEVAL-MKI138V2 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, sensors, power ICs, and analog/mixed-signal devices for industrial, automotive, and consumer applications.

This board belongs to ST's STEVAL (ST Evaluation) series, purpose-built to demonstrate sensor signal conditioning, digital audio processing, and USB host interface interoperability for MEMS microphone-based voice and acoustic sensing systems.

FAQ

Does STEVAL-MKI138V2 require external power or drivers?

No. The board is fully bus-powered via USB and enumerates as a standard USB Audio Class 1.0 device. No additional drivers are needed on Windows 10+, macOS, or Linux distributions with ALSA or PulseAudio support. Firmware is preloaded and ready for immediate use.

Can STEVAL-MKI138V2 interface with third-party MEMS microphones?

It is optimized for MP34DB01 but supports other PDM-output MEMS microphones with matching voltage levels (1.8 V I/O), clock polarity, and data alignment. External microphones must be connected to the designated PDM_INx pins and configured in firmware; no hardware modification is required for compatible devices.

What software tools are supported for configuration and analysis?

ST provides APWorkbench for configuring microphone parameters and analyzing PDM streams. The board also works with standard audio tools (Audacity, Adobe Audition) for PCM recording. ST's STM32CubeMX and Keil MDK are supported for firmware customization and real-time debugging via JTAG/SWD.

Is the PCB layout and schematic available for design reuse?

Yes. ST publishes complete design files-including Gerber, BOM, and schematics-in the official product page (DocID026765). These files are licensed for evaluation and derivative design under ST's Evaluation License Agreement, enabling integration into custom carrier boards or system-in-package implementations.