The GainSpan Audio Application Development Kit (ADK) is a complete reference design that demonstrates an audio streaming application based on the GainSpan GS1011M Wi-Fi Module, audio application board and the associated embedded and mobile software suite. The GainSpan Audio ADK finds use in applications such as remote speaker/microphones, walkie-talkies and baby monitors. It supports a variety of use cases - streaming music from smartphones to a remote speaker or headphones, streaming voice audio data from the audio application board to the smartphone, or walkie-talkie mode to enable two-way audio communication.
The Audio ADK includes the Audio Application board, a complete hardware design package and embedded software including mobile platform APIs and mobile reference applications for iOS based smartphones. An evaluation version of the ADK, the Audio Application Evaluation Kit (AEK) is also available that will include the application hardware and binary-only software.
The Audio embedded software includes the complete audio application software and Wi-Fi and networking stack including mDNS/DNS-SD based discovery methods to discover devices and services available on the wireless network. The Audio mobile reference applications provide customers a foundation to rapidly build custom features suited to their end application.
An evaluation version of the ADK, the Audio AEK is also available that will include the application hardware and binary-only software.
The GainSpan Audio ADK runs on the Audio application board, and supports Wi-Fi streaming to and from an iOS smartphone. On powering up the application board, the Wi-Fi module establishes itself as a Limited AP, and allows users to browse to the list of wireless networks and connect to the Audio ADK board. The mobile application leverages discovery exposed by the Audio embedded firmware application, to enable automatic discovery of available audio services.
After the Limited AP setup is complete, the embedded application software performs application specific initializations for both the GS1011 and audio codec. All communication between the GS1011 and audio codec chip occurs via SPI. The transport mechanism from the audio board to the smartphone used TCP or UDP.
Following initialization, the GS1011 will begin to function as one of the use case models below:
Wi-Fi Streaming Audio to Remote speaker
The GainSpan Wi-Fi streaming demo allows users to select music from their ITunes library or playlists and stream it over to an external speaker connected to the Audio board, using Wi-Fi. The Wi-Fi module receives streaming audio packets from the smartphone and buffers the packets. These packets are then sent to the audio codec chip for decoding, via SPI. This decoded audio stream is then sent to the external speaker. The mobile app has controls to select a song from your music library and play or stop the audio streaming. This application supports mp3 audio streaming at data rates of up to 320Kbps. In Phase 2 (Q1’13), support will be added for other commonly used audio formats such as AAC, WMA and ITunes default MPEG4 (.m4a), at data rates of up to 320Kbps.
Wi-Fi Remote microphone Application
In this use case, the user speaks into the microphone on the Audio application board and the voice data gets transmitted to the smartphone. The GS1011 Wi-Fi module continually reads encoded audio data from the encoder buffer and sends the encoded bytes to the GainSpan mobile application on the smartphone for playback.
This use case showcases two-way walkie-talkie operation, triggered using either the application “Push-to-Talk” (PTT) button on the Audio application board or a “soft” Push-to-Talk button on the Audio application on the smartphone. When the PTT button, located on the Audio ADK board, is pressed, the audio encoder starts to encode and stream audio data over to the smartphone for the duration of the button press. The smart phone application uses a software button as the PTT button, and follows the same behavior as the embedded application. With current implementation, audio transmission is half-duplex, i.e., one unit transmits and the other receives.
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