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Conexant voice board lets you summon Alexa from a Raspberry Pi

Dec 9, 2016 — by Eric Brown 2,381 views

Conexant and Amazon have launched an Alexa Voice Service development kit for the Raspberry Pi 3. The kit includes a Conexant AudioSmart CX20921 voice board.

Since Amazon opened up access to its Alexa Voice Service (AVS) agent inside the Amazon Echo smart speaker/IoT hub, including an open source port to the Raspberry Pi, several projects have emerged for creating Echo-like devices built around the RPi. For example, earlier this year, a Novaspirit Tech hack along these lines was promoted by the Raspberry Pi blog. Now Conexant Systems and Amazon have teamed up on a higher end “AudioSmart 2-mic Development Kit” for the RPi that’s designed specifically for voice-controlled smart home IoT functionality.

AudioSmart 2-mic board (left) and full kit contents
(click images to enlarge)

The kit, which went on sale at Arrow as a “DS20921-EVK” kit for $299, not including the Raspberry Pi board, features a Conexant AudioSmart CX20921 Hands-free Voice Input Processor configured with the Alexa “wake word” technology. The Conexant voice board “captures the user’s voice from anywhere within the room, separates the voice commands from music and voice prompts being played out of the device, even with background noise present, and provides a clean audio signal to the AVS cloud for speech recognition processing,” says Conexant.

The dual-mic board provides high-dynamic range analog-to-digital converters (ADCs), optimized for far-field, and offers features like Smart Source Pickup and AEC-enabled voice barge-in for detecting the Alexa wake words even with extensive background noise or music. The device supports connections to analog microphones and PDM interfaces for connection to digital MEMS mics.

AudioSmart 2-mic mic holder board (left) and block diagram
(click images to enlarge)

The 147 x 78mm board features a micro-USB 2.0 device port, an I2C slave interface for firmware programming, an I2S-to-USB playback codec, and dual ADCs with 8KHz to 96KHz sampling. There’s also an SPI master interface, a UART, and dual GPIOs, one of which is dedicate to wake-on-voice functionality.


The kit is further equipped with stereo microphones with cabling, a mic holder board, a 5V power supply, and other necessary cables. A number of audio jacks are also onboard.

AudioSmart 2-mic kit connected to RPi3 (left) and also to a powered speaker
(click images to enlarge)

“Conexant’s AudioSmart 2-mic Development Kit for Amazon AVS unlocks serious voice capture capabilities, allowing developers to achieve a far better AVS user experience through vital voice processing technologies that overcome acoustic and distance challenges,” stated Steve Rabuchin, Vice President Amazon Alexa. “Utilizing Conexant’s AVS approved solutions will help third-party manufacturers quickly innovate with Alexa.”

Connecting the AudioSmart 2-mic kit to the RPi 3 on YouTube

Further information

The AudioSmart 2-mic Development Kit is available for $299 without the $35 Raspberry Pi 3 at Arrow Electronics. More information may be found at Conexant’s AudioSmart 2-mic product page.

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2 responses to “Conexant voice board lets you summon Alexa from a Raspberry Pi”

  1. Chud Johnson says:

    Kind of a joke to have a huge, $300 board interfacing with a tiny RasPi. What’s the point? Why can’t the RPi do this onboard?

  2. lordofportals says:

    Price is way out of line

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