Audio Mixer

Description

The Audio Mixer application uses the SPARK Wireless Core to send audio streams from two different sources and mix it into a single output audio stream on the receiving device using the SPARK Audio Core.

Audio Mixer Diagram

Figure 16: Audio Mixer Diagram.

Behavior

This application features two Node devices that transmit a 32 kHz/16 bits mono audio stream to a Coordinator device. The Coordinator device receives the two incoming audio streams and mixes them into a single mono audio stream.

The Audio Mixer schedule is made up of 45 timeslots. The first timeslot is dedicated to the Beacon Signal and the following timeslots alternate between the Node 1 and Node 2 devices. A lot of timeslots are used to ensure that the beacon only occurs every 14.65 ms.

The following diagram illustrates the general structure of the schedule used in this application.

Audio Mixer Schedule

Figure 17: Audio Mixer application’s schedule

Coordinator Device

The Coordinator device receives two 32 kHz/16 bits audio mono streams from the two Node devices, mixes them into a single audio mono stream and plays it on the Headphone output.

Since the Coordinator does not send any payload to the Node devices, a Beacon signal is used to keep the connections synchronized.

  • SW1 and SW2 are used to turn the volume up and down respectively. By default, the volume is at the maximum level.

  • LED1 toggles when successfully receiving a payload from Node 1 (almost always on because of the high packet rate).

  • LED2 toggles when successfully receiving a payload from Node 2 (almost always on because of the high packet rate).

Interface

Name

Description

SW1

Volume Up

Raises the volume (default at 100%).

SW2

Volume Down

Lowers the volume.

LED0

N/A

N/A

LED1

Reception Success

Toggle LED when a wireless reception is successful from the Node 1 device.

LED2

Reception Success

Toggle LED when a wireless reception is successful from the Node 2 device.

Node Devices

The two Node devices record audio from their Line-In connector and transmit a 32 kHz/16 bits audio mono stream to the Coordinator device.

  • LED0 toggles every time a packet is successfully transmitted to the Coordinator (almost always on because of the high packet rate).

Interface

Name

Description

SW1

N/A

N/A

SW2

N/A

N/A

LED0

Transmission Success

Toggle LED when a wireless transmission is successful.

LED1

N/A

N/A

LED2

N/A

N/A

Configuration

This application does not require specific configurations.