nRF5340 Audio: Broadcast source

The nRF5340 Audio broadcast source application implements the BIS gateway mode.

In this mode, transmitting broadcast audio happens using Broadcast Isochronous Stream (BIS) and Broadcast Isochronous Group (BIG). Play and pause are emulated by enabling and disabling stream, respectively.

The following limitations apply to this application:

  • One BIG with two BIS streams.

  • Audio input: USB or I2S (Line in or using Pulse Density Modulation).

  • Configuration: 16 bit, several bit rates ranging from 32 kbps to 124 kbps.

Requirements

The application shares the requirements common to all nRF5340 Audio application.

User interface

Most of the user interface mappings are common across all nRF5340 Audio applications. See the User interface page for detailed overview.

This application uses specific mapping for the following user interface elements:

  • Pressed on the broadcast source device during playback:

    • PLAY/PAUSE - Starts or pauses the playback of the stream.

    • BTN 4 - Toggles between the normal audio stream and different test tones generated on the device. Use this tone to check the synchronization of headsets.

  • LED1 - Blinking blue - Device has started broadcasting audio.

  • RGB - Solid green - The device is programmed as the gateway.

Configuration

The application requires the CONFIG_TRANSPORT_BIS Kconfig option to be set to y in the applications/nrf5340_audio/prj.conf file for Building and running to succeed.

For other configuration options, see Configuring the nRF5340 Audio applications and Configuring and testing FOTA upgrades for nRF5340 Audio applications.

For information about how to configure applications in the nRF Connect SDK, see Configuring and building an application.

Building and running

This application can be found under applications/nrf5340_audio/broadcast_source in the nRF Connect SDK folder structure, but it uses .conf files at applications/nrf5340_audio/.

The nRF5340 Audio DK comes preprogrammed with basic firmware that indicates if the kit is functional. See Testing out of the box for more information.

To build the application, complete the following steps:

  1. Select the BIS mode by setting the CONFIG_TRANSPORT_BIS Kconfig option to y in the applications/nrf5340_audio/prj.conf file for the debug version and in the applications/nrf5340_audio/prj_release.conf file for the release version.

  2. Complete the steps for building and programming common to all audio applications using one of the following methods:

After programming, the broadcast source automatically starts broadcasting the default 48-kHz audio stream.

Testing

Note

Nordic Semiconductor seeks to provide seamless interoperability with as many LE Audio devices as possible. However, vendors have reached different levels of maturity in their implementation. Also, different platforms have different methods of connecting, pairing, and streaming. For these reasons, providing a general guide on how to test with external devices is challenging. The suggested approach is to test with Nordic Semiconductor devices on both sides first to verify basic functionalities and get familiar with the solution before using custom devices. Contact Technical Support team if you need assistance.

To test the broadcast source application, complete the following steps:

  1. Make sure you have another nRF5340 Audio DK for testing purposes.

  2. Program the other DK with the broadcast sink application. The broadcast sink device automatically synchronizes with the broadcast source after programming.

  3. Proceed to testing the broadcast source using the User interface buttons and LEDs.

Dependencies

For the list of dependencies, check the application’s source files.