Nordic helps wireless audio transmitter pair up to 100 headsets

     Avantree has released the "Quartet" audio solution that wirelessly connects multiple sets of headphones to a single audio source. The base package includes four pairs of headphones and a transmitter base that wirelessly relays audio content from any device that uses AUX or optical output for audio (such as a TV, projector, or stereo receiver) to the user's headphones

     Avantree uses Nordic Semiconductor's nRF52832 general-purpose multiprotocol system-on-chip (SoC) on both the headset and transmitter base to run a proprietary 2.4 GHz protocol for wireless audio transmission. This solution is designed for applications where multiple sets of headphones need to be connected to the same audio source, such as in classrooms, aged care facilities or outdoor movie theaters. The transmission latency is as low as 7 ms, which eliminates the problem of lip-synching during TV or movie playback. With the nRF52832 SoC's multi-protocol radio, Quartet is able to reliably transmit audio content up to 100 meters outdoors or up to 30 meters indoors. It offers a maximum receive (RX) sensitivity of -96-dBm, a maximum transmit (TX) output of +4-dBm, and an overall link budget of >100dBm.

     This scalable solution can connect up to 100 sets of headphones to a single transmitter base, while each pair has independent volume control, so people with different hearing levels can adjust the volume they want. The "pass-through" feature also allows audio content to be played simultaneously using an existing audio or stereo receiver/speaker system for situations where some listeners prefer not to use headphones.

     This processor-intensive application is powered by the nRF52832 64 MHz, 32-bit Arm® Cortex® M4 processor with floating-point unit (FPU) with ample 512kB of flash and 64kB of RAM. The nRF Connect SDK software development kit for the nRF52832 integrates the Zephyr RTOS, supports applications using Bluetooth Low Energy, Bluetooth mesh and Thread, and includes examples, Bluetooth Low Energy profiles and driver support for all peripherals.

     Lithium-ion battery powered Quartet headsets can last up to 20 hours on a single charge, thanks in part to the ultra-low power consumption of the nRF52832 SoC and the 5.5mA peak RX/TX current and fully automatic power management system of the 2.4GHz radio. Liang Haohua, chief product officer at Avantree, said: "When we were choosing wireless chips for our Quartet earphones, it was very important to have the longest possible battery life. This is especially critical when considering the main usage scenarios, such as users wanting a long Watch TV without charging your headphones."

     While Arm CPU capability, large memory capacity, radio sensitivity, and low-power features were all key factors in chip selection, our main design requirements were the low-latency features and high scalability offered by the nRF52832 SoC. "