Simplified Creation Of Alexa Built-In Smart Home Devices

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Reference design provides simple and cost-effective natural-language understanding and voice-based user interaction for smart appliances

Leveraging the Alexa Voice Service (AVS) Integration for AWS IoT Core is the Amazon-qualified reference design package for smart connected devices by STMicroelectronics, which can be used to create Alexa Built-in products using simple microcontrollers (MCUs).

This integration transforms the way users interact with smart “things,” bringing cloud-based Alexa experiences to items such as toasters, cookers, thermostats, blinds, hairdryers and many others with no need for significant investment in electronic hardware. This could lead to the development of a new generation of products that offer easy and natural user interactions, adaptable smart features and access to cloud services such as cooking advice or reordering of consumables.

The Amazon-qualified solution simplifies the design of Alexa-enabled appliance controllers, with Alexa voice-user-interface software already integrated on the high-performing, energy-efficient MCUs of the STM32 family. Being a powerful 32-bit Arm Cortex-M MCU family, it is ideal for low-cost, small and simple connected devices that require state-of-the-art features such as far-field audio capture and natural-language understanding.

AVS Integration for AWS IoT Core reference design contains a compact 36mm x 65mm main board that combines a high-performance STM32H743 MCU and Wi-Fi module.

Unlike other devices commonly such as digital signal processors (DSPs) and flashless processor that are commonly used for Alexa products, STM32 MCUs integrate all necessary system features in a single chip including:

  • powerful audio front-end processing
  • local wake-word detection
  • communication interfaces
  • memory (RAM and Flash) 

This integration enables the board to have small dimensions and a simple layout for cost-effective deployment in customers’ end products.

Other interesting features

The audio front end delivers outstanding far-field voice detection, even in noisy environments and with closely spaced microphones. It also comes with a free Audio Weaver tool license to help users easily fine-tune their designs.

“The STM32H7’s combination of large internal RAM and Flash, peripheral integration, and high-speed processor enables TalkTo, our high-performance audio front-end, to drive significantly better performance in real-time,” said Paul Beckmann, DSP Concepts Founder and CTO. “TalkTo is delivered through Audio Weaver, so product makers can quickly design, develop and deploy a wide range of voice-enabled products.”

The high-performance STM32 microcontrollers allow users to customise and scale their designs by adding enhancements such as a second wake word, extra local commands and a graphical display to combine with the voice-command capability for an even more compelling user experience.

Further simplifying prototyping and development, the reference design hardware includes an audio daughter board as a separate module. This contains:

  • 1 ST FDA903D audio codec
  • user LEDs and buttons
  • MP23DB01HP MEMS microphones spaced at 36mm for size-constrained products such as power switched plugs. 

The hardware’s modularity lets users implement a custom daughter board if application-specific mic spacing, acoustics and user-interface definitions are needed.

The reference design includes fully developed software that provides the features needed to support Alexa products, including:

  • Audio-capture software
  • Advanced Audio Front End (AFE) with noise reduction, echo cancellation and advanced beam-forming signal processing for far-field audio detection
  • Amazon “Alexa” Wake Word
  • Connectivity to AWS IoT
  • Audio output software

Working with this reference design enables product designers to certify new end products with AVS faster and more easily than bringing up the entire system independently. Both the hardware and software content can be easily adapted to support individual customers’ new-product concepts.


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