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Atmel Digital Audio Platform: Plug and Play

Welcome to the Atmel® Digital Audio Platform application page. Here you will find all the resources needed to develop your audio application.

The days of the CD are numbered. For a lot of people, music is now distributed via compressed data files over the Internet, on USB mass storage devices, on SD cards or in MP3 players and smartphones.

Designing digital audio systems involves accommodating a tangle of different audio formats and communication interfaces. With the Atmel complete Digital Audio Platform, you get a head start to developing high-quality audio systems. That's because the platform works right out of the box – no matter whether your system plays music from an iPhone or has a USB port where users can plug in a thumb drive containing compressed music files.

Some of the technology delivered by the Digital Audio Platform is also applicable to mobile accessories. Learn more at the mobile accessories application page.

Create an Array of Digital Music Applications

Digital Audio Docking Stations for iPod, iPhone or iPad

Docking Station Diagram

If your product needs to play music from an iPod®, iPhone® or iPad®, take a look at the Atmel Made For iPod (MFi) platform. This platform:

  • Streams digital audio from the Apple device and converts it to analog signals for playback
  • Extracts cover art, playlist and song information (ID3) and displays this data on a remote LCD
  • Enables the display of a custom logo on the screen of the Apple device
  • Provides full control of the player

Participants in the Apple MFi licensing program can buy a dedicated Atmel MFi evaluation kit through the program

iPad®, iPhone®, and iPod® are trademarks of Apple Inc., registered in the U.S. and other countries.

Decoders & Playback Systems

 Mass Storage Playback Diagram

Most docking stations and today's car and home stereo systems offer playback of compressed music files stored on mass storage devices such as USB Flash drives and SD cards. These playback and decoding capabilities are also occasionally found in equipment such as guitar amplifiers, keyboards and even treadmills.

Our Digital Audio Platform supports this functionality by offering high-quality MP3, AAC and WMA decoders with a simple licensing scheme. In addition to music decompression, these firmware components also extract metadata, providing access to song, album and artist information.

All Atmel AVR® UC3 microcontrollers support SD cards. AT32UC3 A3 and A4 Series devices have dedicated hardware resources for maximum transfer speed and also support interfacing to MultiMedia Card (MMC) cards or memory sticks.

The Atmel USB protocol stack delivered with the AVR Software Framework offers mass storage class support to access USB storage devices, including a file system management that retrieves the files to play and allows for navigation while playing.

USB Audio Class Devices

 Mass Storage Playback Diagram

USB Audio Class is a class of devices capable of exchanging audio data with a host such as a PC. These include USB PC speakers, USB headsets and USB microphones. Our Digital Audio Platform provides all the firmware you'll need to develop these devices, including the USB protocol stack and audio stream synchronization.

Audio Microcontrollers

Atmel licensed audio firmware intellectual property (IP) requires dedicated audio microcontroller part numbers to operate. This applies to the following firmware libraries:

  • Proprietary Communication Protocol with iPod, iPhone and iPad devices
  • MP3 decoder
  • WMA decoder
  • AAC decoder

The difference between an audio microcontroller (e.g. AT32UC3A0512AU-ALUT) and its standard counterpart (e.g. AT32UC3A0512-ALUT) is not relevant to the user code.

As far as the user code is concerned, audio parts are 100% compatible with the standard devices.

Libraries mentioned above will not work on standard microcontrollers.

From a technical standpoint, the only difference between an audio part (e.g. AT32UC3A0512AU-ALUT) and its standard counterpart (e.g. AT32UC3A0512-ALUT) is the programming of a specific value in a read-only part of the Flash memory of the microcontroller.

This specific programming cannot be erased or modified. Libraries mentioned above will verify that this specific value is present in the microcontroller. If not, code will stall.

Audio microcontrollers can be recognized by the AU letters before the dash in their part numbers.

AT32UC3A0128AU-ALUT12832YesSPIFull Speed Host/OTG0NoLQFP144
AT32UC3A0256AU-ALUT25664YesSPIFull Speed Host/OTG0NoLQFP144
AT32UC3A0512AU-ALUT51264YesSPIFull Speed Host/OTG0YesLQFP144
AT32UC3A1256AU-ALTRA25664YesSPIFull Speed Host/OTG0NoTQFP100
AT32UC3A1512AU-AUR51264YesSPIFull Speed Host/OTG0NoTQFP100
AT32UC3A3256AU-ALUT256128YesSpecializedHi-Speed Host/OTG0NoLQFP144
AT32UC3B0128AU-A2UT12832YesSPIFull Speed Host/OTG0NoTQFP64, QFN64
AT32UC3B0512AU-Z2UR51296YesSPIFull Speed Host/OTG0NoQFN64
AT32UC3C0512AU-ALUT51268YesSPIFull Speed Host/OTG2YesLQFP144

Additional audio part numbers can be created based upon customer demand.

For technical information on an audio device (e.g. AT32UC3A0512AU-ALUT), please refer to the datasheet, architecture manual and technical reference manual of the standard counterpart (e.g. AT32UC3A0512-ALUT). The same applies to other technical documents such as IBIS files and qualification packages.

Tools that support the standard version of AVR UC3 microcontrollers also support the corresponding audio device.

Audio Firmware

The complexity of digital audio systems inherently makes them a difficult design task. Simply establishing basic functionality can be challenging because most of the IP requires highly specialized competence that design houses may not have the time to develop. Our Digital Audio Platform provides a turnkey solution that gives you the resources to leapfrog the daunting task of finding and connecting all the firmware needed to establish basic functionality. This way, you can focus on differentiation and creating value-added features.

The firmware platform consists of an audio player core that takes one input, processes it and sends it to a DAC. The audio player core connects to optional firmware building blocks depending on the signal source and format.

Digital Audio Platform Architecture


*PCP: proprietary communication protocol with iPod, iPhone and iPad devices

  • The input to the system is digital audio that can be streamed from an iPod, a PC or a network, or embedded in a file (compressed or not)
  • The USB stack handles all USB classes that are relevant for audio applications: audio class for streaming, mass storage class for file access and HID class for control.
  • The file system enables navigation and selection of the file to be played, as well as navigation while playing.
  • The communication interface (Com.) handles data transport and control via UART, I2C, SPI or CAN as needed
  • The user interface (UI) provides the means for someone to control the player and display information. It controls the LCD of Atmel evaluation kits and can reproduce album cover art.
  • The synchronization mechanism (Sync.) is needed to synchronize the audio stream. This is described below.
  • The I2S driver sends digital samples to a DAC for analog rendering.
  • Licensed firmware IP cores are premium-quality firmware libraries offered free of charge by Atmel. They require an audio-specific microcontroller to operate. The IP cores include:
    • Protocol stack that allows communications with an iPod, iPhone or iPad device.
    • High-quality audio decoders for the following compressed formats: MP3, AAC, WMA.

For more information about the licensing model of these firmware IP cores, please refer to the Licensing section.

Atmel's customers are responsible for complying with the terms and conditions related to use of these decoders and associated technology, including but not limited to payment of royalties to the respective owners of MP3, AAC, and/or WMA technology, when shipping products supporting these audio compression formats

Solve Synchronization Issues

USB is ubiquitous in the digital audio world, whether it is used for streaming music or accessing audio files. A USB host streams data at a given data rate. A microcontroller then processes the data and transmits it to an audio DAC. As the USB host (which can be the microcontroller itself) and the DAC are connected to separate clock domains, the data rate provided by USB will never fully match the data rate consumed by the DAC.

You can choose from the following methods—all supported by the Atmel Digital Audio Platform—to deal with this digital supply-and-demand challenge.

  • Insert or delete sample data. This method requires the least amount of CPU power and memory but does not provide the best audio quality.
  • Sample rate conversion. With this method, the audio stream is re-sampled to match the frequency of the DAC. This provides acceptable audio quality in most cases, but requires more CPU and memory resources.
  • External clock synthesizer. By clocking the microcontroller with a clock synthesizer capable of tuning the clock frequency by a few PPMs, you can ensure maximum audio quality.

For more information, please refer to the application note AVR32716: USB Audio Class and Synchronization Methods

Performance and Memory Footprints

The following table indicates the performance and memory footprints of essential firmware components.

In summary, 128KB of Flash is sufficient for a basic docking station. For systems that include all decoders, you'll need 512KB of Flash.

Licensed FirmwareCPU Load (MHz)Flash (KB)RAM (KB)
Proprietary Communication Protocol for iPod, iPhone and iPad Devices-354
MP3 Decoder21-252030
WMA Decoder30-4512250
AAC-LC Decoder41-5310060

MiddlewareCPU Load (MHz)Flash (KB)RAM (KB)
USB Mass Storage Stack<1183
FAT12/16/32 Library (with Navigation)-201
HMI (Buttons and LCD)-181
JPEG Decoder 625x625 Pixels41-5310060

Please note that enabling navigation while playing consumes a lot of RAM since an image of the mass storage device needs to be built. You might need an external memory, depending on the application and the selected microcontroller.

Other Supported Functions

Open-Source MP3 Decoder
Atmel is offering the MAD MP3 decoder from Underbit Technologies as a part of the AVR Software Framework (ASF). This decoder is licensed under the GPL open-source license terms and can be executed on any AVR UC3 32-bit microcontroller.

Customers are responsible for complying with the licensing terms of this decoder and associated technology, including but not limited to payment of royalties to the owners of MP3 technology when shipping products that support MP3 audio decompression.

WAV Support
Although rarely used because of the large file sizes, playback of the WAV format is also supported.

JPEG Decoder
To render album artwork, a JPEG decoder is also available through the ASF. Please note that it uses about 60KB of RAM; you may require external RAM depending on the application and the selected microcontroller.

Functions Not Supported

There are, of course, many audio standards in use worldwide. If you require a format that is currently not supported, please contact your local sales representative or email our dedicated support channel: We will gladly examine your request.

Atmel Digital Audio Platform Components

The table below summarizes the key components of our Digital Audio Platform.

 Works on Audio AVR UC3 Microcontrollers OnlyWorks on All AVR UC3 Microcontrollers
Proprietary Communication Protocol for iPod, iPhone and iPad DevicesX 
Spirit DSP MP3 DecoderX 
WMA DecoderX 
AAC-LC DecoderX 
MAD MP3 Decoder X
WAV Decoder X
USB Audio, Mass Storage and HID Classes X
File System Management with Navigation While Playing X
Audio Synchronization X
JPEG Decoder X
HE-AAC DecoderNot Supported Yet 

Audio Development Kits

Evaluate the Digital Audio Platform through one of our development kits built around our audio microcontrollers.


This kit demonstrates the Atmel AVR AT32UC3A3256AU microcontroller, which combines an unrivalled selection of communication interfaces such as Hi-speed USB with On-The-Go (OTG) , a dual SD card interface, NAND Flash with ECC and stereo 16-bit DAC, making it the perfect fit for Hi-Fi audio decoding and streaming applications. The kit contains reference hardware and firmware for playing MP3 files from mass storage devices, and demonstrates Atmel's patented QTouch capacitive touch control.

The kit also supports Atmel licensed audio firmware IP cores. Get more information on the EVK1104AU evaluation kit.



This kit implements a Hi-Fi decoding and streaming application demonstrating the Atmel AVR AT32UC3A0512AU microcontroller together with Atmel's patented QTouch capacitive touch control. The kit contains reference hardware and software for playing MP3 files from mass storage devices. Its microcontroller offers 512KB of Flash memory as well as Ethernet connectivity.

The kit also supports Atmel licensed audio firmware IP cores. Get more information on the EVK1105AU evaluation kit.



This kit supports development of Made For iPod (MFi) audio docks. It contains all required reference hardware and software for control and digital audio streaming from iPod, iPhone and iPad devices, and demonstrates Atmel's patented QTouch capacitive touch control.

Get more information on the EVK1105-MFi Evaluation Kit.


What If I've Already Bought a Kit?
If you own a kit that does not include an audio microcontroller, namely an EVK1104 or an EVK1105, Atmel will upgrade your kit free of charge. Please contact your local sales representative or email our dedicated support channel at for details.

Audio Firmware Packages and Licensing

Making Licensing Easy
Audio system designers have long relied on open-source firmware IP cores; however, the drawback is that their licensing terms often require that you make your complete application code publicly available.

An obvious workaround is commercial licensing of firmware, but this often involves a considerable investment in time and money. After you obtain the license, you need to port the IP to your target microcontroller and optimize.

Our Digital Audio Platform offers a painless solution to this dilemma. All licensed audio firmware IP cores are delivered free of charge. Since they are based on commercial license agreements, you can keep your proprietary code confidential while freely using these high-quality firmware IP cores. And because they come with a simple click-through license agreement, they are ready to be used right away. You can then spend your time and effort designing differentiated audio products.

Licensed Audio Firmware IP Cores

Proprietary Communication Protocol with iPod, iPhone and iPad Devices
This firmware stack is only available to customers who participate in the MFi licensing program. It is part of a firmware package that is available at Apple's authorized MFi component distributor. Customers who download this package will be given instructions on how to register and accept the license agreement before they can use the library.

Spirit DSP MP3 Decoder
To receive the Spirit DSP MP3 decoder library files, please register at

You will receive the object code shortly after verification and upon approval from Atmel. Customers are responsible for complying with the terms of this decoder and associated technology, including but not limited to payment of royalties to the owners of the MP3 technology when shipping products supporting MP3 decoding.

WMA Decoder
To receive the WMA decoder library, please register at

Shortly after verification that you are a Microsoft Windows Media Components licensee (final product or interim product agreement) and upon approval, you will receive the object code.

If you are not yet a Microsoft Windows Media Components licensee, you can still evaluate the code by registering at:
The firmware that you will receive is limited in the number of frames it can decode, but is perfectly suited for evaluation of the Atmel WMA decoder.

Customers are responsible for complying with the terms of this decoder and associated technology, including but not limited to payment of royalties to Microsoft when shipping products supporting WMA decoding.

Fraunhofer IIS AAC Decoder
To receive the Fraunhofer IIS AAC-LC library, please register at

Shortly after verification and upon approval from Atmel, you will receive the object code. The library is an evaluation version of the AAC-LC decoder. While it is limited in the number of frames it can decode, it is perfectly suited for evaluation of the decoder.

If you are interested in the non-limited version, please contact your local sales representative or send an email to Certain restrictions may apply.

Customers are responsible for complying with the terms of this decoder and associated technology, including but not limited to payment of royalties to the owners of AAC technology when shipping products supporting AAC decoding.

Available Audio Firmware Packages

Atmel has bundled the IP into certain firmware packages to make it easier for you to choose the right set of features.

To obtain these packages, you must register and accept the agreements for all relevant libraries, then send an email to to request one of the packages below. Should you need a package that is not listed below (e.g. Spirit DSP MP3 decoder + Fraunhofer IIS AAC-LC decoder (evaluation version), please send an email to

Important notice:
The Proprietary Communication Protocol for iPod, iPhone and iPad devices can only delivered through Apple's MFi licensing program. Firmware packages listed below that allow the execution of this firmware stack (column, "iPod dock firmware"), do not include the Proprietary Communication Protocol for iPod, iPhone and iPad devices. If you participate in Apple's MFi licensing program, you can obtain it from Apple's authorized MFi component distributor and include it in the package. For support, please send an email to

 iPod Dock FirmwareSpirit DSP MP3 DecoderWMA DecoderFraunhofer IIS AAC-LC Decoder (Evaluation Version)
Package_m X  
Package_w  X 
Package_alce   X
Package_mw XX 
Package_mwalce XXX

Other Audio Resources

Applications Notes
Dedicated audio application notes are available to help you design with our platform.

* MP3 Audio decoder from Underbit technologies™, GPL license
** MP3 Audio decoder from Spirit DSP, commercial license

Internal DAC
Selected UC3 microcontrollers have a stereo DAC that can be used to render audio. Although this integrated DAC will not deliver the same performance as specialized external CODECs, it can be used in many applications to lower costs. For more information, please refer to the application note AVR32120: Using the 32-bit AVR UC3 Audio Bitstream DAC Driver.

External DAC
To obtain the best audio quality, use an external DAC such as the Atmel AT73C246 or AT73C240. Atmel also recommends the Bang & Olufsen ICEpower MobileSound 3, a fully digital, low-power single chip stereo Class D speaker amplifier, headphone amplifier and audio digital signal processor. ICEpower MobileSound 3 contains:

  • A stereo Class D high-power speaker amplifier with 2x 920mW output power and 100dB SNR
  • A stereo true ground headphone amplifier with 2x 25mW output power and 94dB SNR
  • Fully digital interface with three switchable digital I2S/PCM inputs and outputs
  • Light CODEC functionality
  • Integrated ICEpower DSP (ICEDSP) core for sound-enhancing digital signal processing such as:
    • SmartBass adaptive dynamic bass enhancement
    • SmartEQ flexible, fully parametric 5-band equalizer
    • SmartDRC advanced parametric multistage compressor/limiter system
    • Digital volume control

ICEpower MobileSound 3 is available in a 3.0mm x 2.6mm package. The system's integrated amplifier can be used to directly drive speakers in small cabinets. Its DSP capability helps correct the frequency response of low-cost speakers to generate the best audio quality.

Additional Atmel Resources

We've developed our innovative technology to give you the flexibility to design a variety of differentiated products.

  • Atmel QTouch Library lets you implement robust, reliable capacitive touch buttons, sliders and wheels using standard microcontrollers. Using the library lets you focus on differentiating features and innovative, elegant user interfaces.
  • Atmel Studio 5 integrates the AVR Software Framework, which supports audio functions and enables easy access to differentiating technology in our microcontrollers.
  • RF4CE enables next-generation, RF-based remote controls, supported by ZigBee hardware transceivers and software protocol stacks.
  • Accessory authentication provided by Atmel CryptoAuthentication™ ICs makes it easy to control the accessory market by limiting access to approved vendors only.

Here is a summary of Atmel products that you can use in your audio application:

MicrocontrollerAudio DACCapacitive TouchRF TransceiverHardware Security


AT73C240 Audio DAC

AT73C246 Audio DAC and Power Management

Buttons, Sliders and Wheels

QTouch Library

maXTouch™ Touchscreen Controller



ZigBit® Modules

Atmel CryptoAuthentication