Published November 7, 2017. Copyright © 2017 Synaptics Incorporated. All rights reserved. PN: 190-000284-01 Rev. A
AudioSmart® 2-Mic Development Kit for Amazon AVS
AudioSmart Product Brief
AudioSmart Hands-Free 2-Mic Development
Kit for Amazon AVS with Synaptics Voice
Processing and Alexa Wake Word
Product Overview
Synaptics’ AudioSmart® 2-M ic Dev el opme nt Ki t for Amazon
AVS features Synaptics’ CX 20921 Voi ce Input Processor
with embedded hands-free voice processing technology and
preloaded Alexa™ wake word. The kit is designed to help
manufacturers and developers quickly and easily build
smart home device prototypes that offer an ideal voice user
experience.
Enabling speech recognition from a distance requires
overcoming substantial acoustic challenges related to echo
cancellati o n, bac kground noi se, micr ophone posit ion,
speaker placement and more. Synaptics’ dual-microphone
voice processing solution is designed to recognize the
Alexa wake word and deliver speech requests for
processing, from anywhere in a room, even in noisy, real-
world conditions. The solution also enables voice barge-in
capabilities, allowing users to interrupt their Alexa device
when it's playing sound.
The AudioSmart 2-Mic Development Kit for Amazon AVS
reduces engi ne er i ng time and costs as soc i a t ed w i th
developing noise-robust voice-enabled devices.
The core component of the kit is Synaptics’ AudioSmart
CX20921 Voic e Inp ut Pr oces sor ru nni ng its i ndust r y -leading
hands-free voice pre-processing software technology. The
Synaptics hands-free voice input processor system
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 speech recognition engine.
This solution ensures that the speech recognition engine
hears only the user's command, and nothing else -
providing consistent accuracy and an ideal end-user
experience.
The AudioSmart 2-Mic Development Kit for Amazon AVS is
compatible with the Amazon AVS for Raspberry Pi (RPi)
Project.
Features
• Cost-effective hands-free voice interaction with
only two microphones
• Proprietary Smart Source Pickup™ (SSP)
technology detects voice and cancels noise from
all directions around the device (omnidirectionally),
even if noise sources are from the same direction
as the user
• Best-in-class voice barge-in is enabled by full
duplex stereo acoustic echo cancellation (AEC)
that detects the Alexa wake word even during loud
playback of music or voice prompts
• High-dynamic range a nal og -to-digital converters
(ADC) optimized for hands-free voice appli cations,
supports connections to analog microphones and
PDM interfaces for connection to digital MEMS
microphones
• Integrated voice trigger function that supports low
system power Wake-on-Voice (WoV) functio n
• Multiple Integrated Interchip Sound (I2S) serial
data interfaces
• Inter-Integ r ated Cir c uit (I 2C) serial control interface
• SPI for low-cost flash support
Applications
• Home Smart appl iances
• Home Gateway/C ontr oll er
• Lighting
• Speaker/Sound Bar
• Telepresence
• TV/Set-Top Box
• Internet of Thing s (IoT) devices
Published November 7, 2017. Copyright © 2017 Synaptics Incorporated. All rights reserved. PN: 190-000284-01 Rev. A
AudioSmart® 2-Mic Development Kit for Amazon AVS
AudioSmart Product Brief
AudioSmart 2-Mic Development Kit for Amazon AVS Evaluation Board
Kit Contents
The Synaptics CX20921 AudioSmart 2-Mic Development Kit for Amazon AVS includes the following:
• CX20921 Evaluation Board, G600Z-C00647R30
• Microphone module with two omnidirectional mics
• Microphone holder board
• Stereo 3.5mm male-to-male audio cable
• Micro-USB cable
• Type A to Type B USB cable
• Cable assembly
• +5V power supply for the CX20921 Evaluation Board
Note: Other components required for board evaluation are the Raspberry Pi (RPi3) and powered loudspeakers. These items are not
included in the kit.
Published November 7, 2017. Copyright © 2017 Synaptics Incorporated. All rights reserved. PN: 190-000284-01 Rev. A
AudioSmart® 2-Mic Development Kit for Amazon AVS
AudioSmart Product Brief
AudioSmart 2-Mic Development Kit for Amazon AVS Specifications
Physical Characteristics
Dimensions (mm)
78 x 147 x 1.6 ± 10%
Operating temperature
125°C/0°C (Max/Min)
External Interfaces
USB
Full speed USB2.0 Device, supporting up to five fully configurable endpoints.
I2C slave
J9: Maximum clock frequency 1 MHz (fast mode plus). The I2C connection is used to
program the firmware on the CX20921 Evaluation Board.
I2S-to-USB Playback CODEC
• Two channel I2S out available through pin multiplexing.
• Sample rate support from 8 KHz to 192 KHz.
• Independent clock source
• (U1) Routes processed microphone signals to Amazon AVS. Mic signals are processed
via AudioSmart hands-free voice input processing software.
SPI Master
Maximum clock frequency up to 50 MHz. See product Application Note for list of supported
SPI Flash devices. U12 is the SPI Flash component used to store CX20921 firmware.
UART
J24: Maximum baud rate up to 1.5625 Mbps
GPIO1/2
• GPIO1: For WoV function that toggles to wake external device when the CX20921
recognizes an audio wake trigger event. Used for low-power embedded trigger mode.
• GPIO2: Generic GPIO
Master Clock
Default: Off
Audio Characteristics
ADC
Two high performance ADCs with preamplifiers. Supports sample rates from 8 to 96 KHz.
ADC low power mode
An enhanced mode that enables reduced power consumption.
ADC Performance
• Dynamic range: 106 dB at 0 dB
• THD –84 dB at –1 dBFS
Microphone Bias
Two microphone bias support
Microphone Module Features
Microphone holder board
dimensions
38.1 x 147.32 x 1.6 ± 10%
Operating temperature
125°C/0°C (Max/Min)
Microphone Module
Specifications
• Two stereo omnidirectional microphones
• Microphones are connected via 3.5 mm male audio cable to J19
Connectors
Stereo 3.5 mm male-to-male
audio cable
J25: Sends the audio response from the Amazon AVS to the CX20921 Evaluation Board.
Audio response is routed to the powered speakers via the I2S-to-USB Playback CODEC.
Micro-USB cable
J1: Sends the processed microphone signal to the Amazon AVS.
Type A to Type B USB cable
J9: Used to flash the CX20921 Evaluation Board with firmware.
Cable assembly
P2.pin 14/P2. pin 15: Connects GPIO1/GND pins from EVK to host processor board (such as
the Raspberry Pi).
Power Supply
Power Supply input power
5V, min 2A
Published November 7, 2017. Copyright © 2017 Synaptics Incorporated. All rights reserved. PN: 190-000284-01 Rev. A
AudioSmart® 2-Mic Development Kit for Amazon AVS
AudioSmart Product Brief
AudioSmart 2-Mic Development Kit for Amazon AVS Components
CX20921 Evaluation Board Block Diagram
Published November 7, 2017. Copyright © 2017 Synaptics Incorporated. All rights reserved. PN: 190-000284-01 Rev. A
AudioSmart® 2-Mic Development Kit for Amazon AVS
AudioSmart Product Brief
Ordering Information
Distributor
URL
Part Number Description
Arrow Electronics
https://www.arrow.com/en/products/
ds20921-evk/conexant-systems
DS20921-EVK
AudioSmart 2-Mic Development Kit, for Amazon AVS
The devices in this publication are lead-free (Pb-Free) and China RoHS compliant.
Contact your local Synaptics sales office for advanced software options.
To learn more about Synaptics and its development kit, please visit https://www.synaptics.com/partners/amazon/ds20921
To learn more about Amazon Alexa Voice Service and access the Amazon AVS API reference guide, visit:
https://developer.amazon.com/alexa-voice-service/
Trademarks
Synaptics, the Synaptics logo, and AudioSmart, are trademarks or registered trademarks of Synaptics Incorporated or its
affiliates in the United States and/or other countries.
Notice
This document contains information that is proprietary to Synaptics Incorporated (“Synaptics”). The holder of this document shall treat all
information contained herein as confidential, shall use the information only for its intended purpose, and shall not duplicate, disclose, or
disseminate any of this information in any manner unless Synaptics has otherwise provided express, written permission.
About Synaptics
Synaptics is the pioneer and leader of the human interface revolution, bringing innovative and intuitive user experiences to intelligent devices.
Synaptics’ broad portfolio of touch, display, biometrics, voice, audio, and multimedia products is built on the company’s rich R&D, extensive
IP and dependable supply chain capabilities. With solutions designed for mobile, PC, smart home, and automotive industries, Synaptics
combines ease of use, functionality and aesthetics to enable products that help make our digital lives more productive, secure and enjoyable.
(NASDAQ: SYNA).
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