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.

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.

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.