Swiss semiconductor firm ST Microelectronics is simplifying the creation of Alexa built-in smart home devices with an Amazon-qualified reference design.

The reference design eases development of simple and cost-effective natural-language understanding and voice-based user interaction for smart-home devices and smart appliances. It is qualified by Amazon to use Alexa voice service (AVS) integration for AWS IoT Core for MCU devices.

The AVS integration for AWS IoT Core has the ability to transform the way users interact with smart things, bringing cloud-based Alexa experiences to items such as toasters, cookers, thermostats, blinds and hairdryers with no need for significant investment in electronic hardware. This could hasten the end for traditional buttons and dials, leading to products that offer easy and natural user interactions, adaptable smart features, and access to cloud services such as cooking advice or reordering of consumables.

STM’s Amazon-qualified product jump-starts the design of Alexa-enabled appliance controllers, with Alexa voice-user-interface software already integrated on high-performing MCUs in the STM32 family. The energy-efficient STM32 32bit Arm Cortex-M MCU is suitable for low-cost, small, and simple connected devices that require features such as far-field audio capture and natural-language understanding.

“We believe the AVS integration for AWS IoT Core can revolutionise users’ expectations of smart devices by enabling easier access to their powerful features and delivering more rewarding experiences,” said Daniel Colonna, marketing director at STM. “Our reference design leverages the inherent strengths of STM32 microcontrollers to enable cost-efficient products with unbeatable functionality, small size and fast time to market.”

The reference design contains a 36 by 65mm main board that combines an STM32H743 MCU and wifi module.

Unlike other devices commonly used for Alexa products, such as digital signal processors and flashless processors, STM32 MCUs integrate all necessary system features including audio front-end processing, local wake-word detection, communication interfaces and memory, including RAM and flash, in a single chip. This integration enables the board to have small dimensions and a simple layout for cost-effective deployment in end products.

The audio front end delivers far-field voice detection, even in noisy environments and with closely spaced microphones. Created by STM partner DSP Concepts, the front end comes with a free Audio Weaver tool licence to help users 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 CTO. “TalkTo is delivered through Audio Weaver, so product makers can quickly design, develop and deploy a wide range of voice-enabled products.”

Leveraging the features of the STM32 microcontrollers, users can 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 a more compelling user experience.

Further simplifying prototyping and development, the reference design hardware includes an audio daughter board as a separate module. This contains an STM FDA903D audio codec, user LEDs and buttons, and two 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 software that provides the features needed to support Alexa products.

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

The bill of materials for the reference design is engineered to be less than $10 when purchasing the components in high volumes.