Nordic Semiconductor's nRF24Z1 is the ideal transceiver for wirelessly linking headphones to music players. The HPR1 headphone reference design is available to demonstrate the capability of the nRF24Z1 in this application.

The nRF24Z1 single-chip 2.4 GHz, RF transceiver is a wireless CD-quality audio streaming device with 4 Mbit/s bandwidth to stream true "lossless" digital audio. It uses adaptive frequency hopping to avoid clashes with other devices operating in the 2.4 GHz band. The chip is manufactured using low-cost 0.18µm CMOS fabrication, and is supplied in a 36-pin, 6 by 6-mm QFN package.

The HPR1 headphone reference design comprises an audio transmitter (ATX) PCB, an audio receiver (ARX) PCB and a daughterboard used for in-system programming and debugging. The kit also includes a flat flexible cable with connector and Nordic's EEPROM programmer USB dongle and USB cable. These items are available free of charge from Nordic Semiconductor.

The system is controlled by a microcontroller (MCU) on the ATX board. Both the ATX and ARX PCBs feature a user interface comprising six pushbuttons and an LED. The user interface can be easily modified.

The HPR1 headphone reference design features functionality similar to that of proprietary wireless headphones. The reference kit demonstrates the feasibility of the nRF24Z1 in music players and provides comprehensive guidance for the implementation of an nRF24Z1-based design. A detailed technical specification can be found in the document entitled "nRF24Z1 Headphone Reference Design 1, nRF24Z1-HPR1" available here

The hardware and published design files aid customers who want to design their own products based on the nRF24Z1. The design files need only small alterations (for example, to the printed circuit board (PCB) form factor and placement of the user interface buttons on the PCB) to convert them to production-ready files. The files are available here. (Click on "more info" under the "Development Tools" heading on the right navigation menu to download the files.)

Note that the EEPROM featured on the ARX and ATX boards holds the nRF24Z1 configuration and a boot image for the internal nRF24Z1 MCU. This device uses on-chip RAM. The production version of the nRF24Z1 uses a firmware image stored in an on-chip ROM. This means that only the configuration settings are loaded from EEPROM.

The documentation for the Headphone Reference Design has been written for the ROM version of nRF24Z1. However, if a RAM version is used, the nRF24Z1_firmware_2_0.hex file needed for the EEPROM boot image is available from the same place as the other development tools (here).

For more information on the nRF24Z1 or HPR1 headphone reference design please contact Nordic Semiconductor at nRF@nordicsemi.no