Summary of Contents for Nordic Semiconductor NRD24V1
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Headset Reference Design nRD24V1 User Guide v1.0 All rights reserved. Reproduction in whole or in part is prohibited without the prior written permission of the copyright holder. February 2007...
User Guide Liability disclaimer Nordic Semiconductor ASA reserves the right to make changes without further notice to the product to improve reliability, function or design. Nordic Semiconductor ASA does not assume any liability arising out of the application or use of any product or circuits described herein. Life support applications disclaimer These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be expected to result in personal injury.
IP (VoIP) applications. The quality of the audio in this design is the same as the audio quality in tele- phony. This user guide describes the nRD24V1 system, HW modules and gives guidelines on how to take this ref- erence design and build it into a headset application for a finished product.
Headset Reference Design v1.0 System Description The headset unit can be used to communicate with either a USB dongle or an audio dongle. Note: The audio dongle is simply a headset unit with different firmware and jumper settings. Figure 1. ”Headset unit with a USB configuration” and Figure 2. ”System diagram of headset unit with USB configuration”...
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Application Voice Protocol Audio Audio Buttons Figure 4. System diagram of headset unit with audio dongle configuration The headset unit and the audio dongle are based on the same hardware. Both use an audio codec to pro- vide coding and decoding of the analog audio signals to 16-bit linear PCM code. This bit stream is pro- cessed by the micro controller to an 8-bit a-law bit stream, which is sent to the nRF24L01 for wireless transmission.
The microphone input has a 1.1 VDC bias for driving the microphone. The loudspeaker outputs are a differential class D output and need some external filtering components. Revision 1.0 Audio codec MCU crystal Figure 5. nRD24V1 radio module Page 7 of 25...
3.1.2 Micro controller The micro controller is an AVR, ATmega88 and runs on a 4.096 MHz crystal. The micro controller’s main tasks are: • Setting up codec and RF circuits. • Converting 16 bit PCB audio samples from the codec to 8 bit a-law samples to the radio circuit. •...
Headset Reference Design v1.0 3.1.7 Specifications Operating conditions Supply voltage Current consumption Radio frequency Output power PCB attributes PCB type PCB dimension (length x width x height) Revision 1.0 Status 1.9 - 3.6 V Idle < 1 mA average (15 mA peak) at 2.5 V supply Connected <...
Application board The nRF24L01-VHR1 application board contains all peripherals necessary to build a complete audio mod- ule from the nRF24L01-VHR1 radio module. Radio module Linear regulator Jumpers Audio interface Jumpers Switch 6 3.2.1 Audio interface This module can be used to set up a wireless audio link, for example, from a PC to a headset. The radio module is the same for both sides of the link, but needs some external components to interface with either the PC audio connections, or a microphone/loudspeaker for a headset.
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Headset Reference Design v1.0 3.2.1.1 Headset interface The loudspeaker(s) are driven differentially, and need some filtering due to the class D output amplifier of the audio codec. Figure 7. ”Loudspeaker interface” shows a typical filter network that can be used for driv- ing a headset loudspeaker.
PC loudspeaker out 3.2.2 Jumpers The application board can be set up to interface a headset microphone and loudspeaker, or a PC audio outlet by placing the jumpers as shown in Table 3. ”Audio filter settings” below. The filter components mounted should be appropriate for most headset loudspeakers.
Headset Reference Design v1.0 3.2.5 Buttons There are five buttons on the application board and these are connected to the AVR micro controller on the radio module as shown in Figure 10. ”Button mapping”. AVR pin 24 3.2.6 Programming The radio module can be programmed through the 6-pin ISP connector (P1) with an AVR programming tool like the STK500 from Atmel.
The USB dongle is mounted on a 0.8 mm, 4-layer FR4 circuit board, with components on both sides of the board. MCU crystal Figure 11. nRD24V1 USB dongle top side USB MCU EE Prom Figure 12. nRD24V1 USB dongle bottom side Revision 1.0...
Headset Reference Design v1.0 3.3.1 USB Interface The USB interface is handled by the Sonix SN11220 USB Audio Controller. All the USB communications are handled by the SN11220. The audio samples are 16 bit linear PCM on the I2S port, where the micro controller acts as a bus master (PADFUN mode 4’1100 in the SN11220ACF data sheet).
3.3.6 Specifications Operating conditions Supply voltage Current consumption Radio frequency Output power PCB attributes PCB type PCB dimension (length x width x height) Revision 1.0 Status 4.5 - 5.5 V Idle < 24 mA Connected < 28 mA 2402-2478 MHz 0 dBm Table 4.
Headset Reference Design v1.0 Hardware design guidelines This chapter describes important issues that might affect you when developing the headset reference design for a finished product. The USB dongle can be used as-is, but the headset must be redesigned to fit into a headset for a finished product.
4.1.2.2 Audio interface The audio interfaces from the application board should be used when using the radio module as-is in a design. The audio interfaces are matched to the used audio codec on the radio module. Using a different codec or load on the interfaces requires redesign of the audio interfaces. 4.1.3 Crystals The crystal used as the RF crystal is a 16 MHz crystal.
Headset Reference Design v1.0 USB dongle 4.2.1 Antenna The USB Dongle uses a PCB quarter wave antenna. The USB Dongle is production ready, and any modi- fications to the antenna are only required as part of the antenna tuning process to compensate for plastic housing, and so on.