Can You Use a Wireless Headset with an Audio Interface?

Yes, you can use a wireless headset with an audio interface as long as the audio interface has a headphone jack. Most audio interfaces have a 1/4 inch headphone port, compatible with Bluetooth transmitters that often have a 3.55mm headphone jack. To use a Bluetooth transmitter, you'll need a 1/4 inch headphone adapter.

Bluetooth Protocols

Most wireless headsets use Bluetooth and operate under various protocols for streaming audio. Let's explore these protocols and their significance:

A2DP (Advanced Audio Distribution Profile)

A2DP is used for streaming audio from sources like smartphones or computers to a pair of headphones. It supports stereo audio and allows for bi-directional audio streaming, including microphone voice for hands-free calls. The standard audio interface for A2DP is the low complexity subband codec (SBC), which offers good audio quality while maintaining low computational complexity. SBC supports mono and stereo streams and can handle sampling frequencies up to 48 kHz. Additionally, A2DP can support advanced audio coding (AAC) at higher sample rates up to 96 kHz.

AVRCP (Audio/Video Remote Control Profile)

AVRCP is another profile often paired with A2DP. It allows for remote control of the Bluetooth host, such as adjusting volume, play/pause, and controlling playback.

HSP (Headset Profile)

HSP is used primarily with mobile phones and gaming consoles. Its associated audio interface is SCO (Synchronous Connection-Oriented), which typically uses CVSD (Continuous Variable Slope Delta) or PCM (Pulse Code Modulation), often resulting in lower voice quality than SBC or AAC due to lower sampling rates such as 8 or 16 kHz.

HFP (Hands-Free Profile)

HFP is used for making hands-free calls. Its audio interface is also SCO, with CVSD or PCM, and audio streams at a lower sample rate compared to A2DP.

Implementation Details

I have experience with implementing a wireless Bluetooth headset, using A2DP and HFP with the Microchip BM64 Bluetooth module. The BM64 has an integrated Bluetooth stack, simplifying the firmware requirements. The Bluetooth module supports high-speed UART for controlling Bluetooth functions and various protocols, as well as an I2S (Inter-IC Sound) interface for audio. The module handles all audio decoding and encoding, with audio coming in as simple 16 or 24-bit PCM on the I2S interface.

In my application, when streaming music from an iPhone, the Bluetooth module sends the microcontroller stereo 16-bit audio at 48 kHz. If a phone call comes in, the BM64 switches the audio stream to 8 kHz, and the microcontroller receives notifications for both the protocol switch and sample rate change. The microcontroller then adjusts the sample rate of the DAC to match. If the DAC doesn't support 8 kHz, the microcontroller would need to up-sample the audio to 48 kHz.

The complete source code for my application is available through Microchip's Harmony platform, under the apps/bluetooth/audio folder in the current 2.06 release.

Conclusion

With the proper setup and compatible hardware, you can seamlessly use a wireless headset with an audio interface. Understanding the various Bluetooth profiles and their audio interfaces will help you make informed decisions when choosing your audio equipment.