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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
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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 pr
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Headset Reference Design v1.0 Contents 1 Introduction .................................................................................................4 2 System Description .....................................................................................5 3 Hardware description ..................................................................................7 3.1 nRD24V1 Radio module ......................................................................7 3.1.1 Audio Codec..................
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User Guide 1 Introduction This user guide is for the nRD24V1 headset reference design, a voice quality wireless headset for Voice over 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. The nRD24V1 consists of a USB d
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Headset Reference Design v1.0 2 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” illustrate the headset unit with a USB configuration. Headset USB unit dongle Figure 1. Headset unit with a USB configuration Applicat
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User Guide Application Application Voice Voice Protocol Protocol ShockBurst ShockBurst MCU MCU PHY PHY I/O I/O RF RF I/O I/O Audio Audio DAC DAC Out Out Audio Audio ADC ADC In In Buttons LED LED 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
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Headset Reference Design v1.0 3 Hardware description 3.1 nRD24V1 Radio module The radio module is a complete system for telephone quality wireless headset applications intended for VoIP. It can be used in a headset, or in an audio module for connection to a PC audio outlet. There are 6 GPIOs for buttons or LEDs on the radio module. The radio module is mounted on a 25 x 12 x 0.8 mm, 4-layer FR4 circuit board, with components on one side. 5 1 4 2 3 1 RF crystal 4 Audio codec 2 nRF2
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User Guide 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. • Converting 8-bit a-law samples from the radio circuit to 16-bit linear PCM. • Handling the RF protocol. Additionally, five button inputs are scanned and one output is provided fo
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Headset Reference Design v1.0 3.1.7 Specifications Operating conditions Status Value Supply voltage 1.9 - 3.6 V Current consumption Idle < 1 mA average (15 mA peak) at 2.5 V supply Connected < 7 mA average (15 mA peak) at 2.5 V supply Radio frequency 2402-2478 MHz Output power 0 dBm Table 1. Electrical Specifications PCB attributes Description PCB type 0.8 mm 4 layer FR4 PCB dimension (length x width x height) 25 mm x 12 mm x 0.8 mm Table 2. Physical Specifications Revision 1.0 Page 9 o
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User Guide 3.2 Application board The nRF24L01-VHR1 application board contains all peripherals necessary to build a complete audio mod- ule from the nRF24L01-VHR1 radio module. 6 7 1 8 2 9 3 4 10 5 11 1 Radio module 7 P3 external power 2 Linear regulator 8 Batteries 3 Jumpers 9 Switches 7 and 8 4 Audio interface 10 ISP programming 5 Jumpers 11 Buttons 6Switch 6 Figure 6. Application board components 3.2.1 Audio interface This module can be used to set
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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. The filter depends on the chosen loudspeaker. The microphone can be connected directly to the codec input. The codec input has a 1.1 V supply that can power a typical headset microphone. 100
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User Guide C1 R1 C2 PC loudspeaker out AIN 2.2u 1k 2.2u R2 47 Figure 9. PC output interface 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. CJ2 CJ3 W1 W2 Connecting to Connect to headset Connect to headset Mount jumpers 4 Mount
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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”. SW1 AVR pin 23 SW2 SW3 SW4 AVR pin 24 AVR pin 25 AVR pin 26 SW2 AVR pin 27 Figure 10. Button mapping 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 programming procedure is a
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User Guide 3.3 USB dongle The USB dongle establishes a wireless audio link with the radio module in a headset and is identified as an audio device in the PC operating system. The USB dongle is mounted on a 0.8 mm, 4-layer FR4 circuit board, with components on both sides of the board. 2 3 1 4 1 MCU 3 nRF24L01 2 MCU crystal 4 RF crystal Figure 11. nRD24V1 USB dongle top side 1 2 3 1 USB MCU 3 ISP connector 2 EE Prom Figure 12. nRD24V1 USB dongle bottom si
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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). The audio frame signals are derived from the 2.048 MHz clock output from the USB controller. This synchronizes the audio frames with the USB audio frames. T
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User Guide 3.3.6 Specifications Operating conditions Status Value Supply voltage 4.5 - 5.5 V Current consumption Idle < 24 mA Connected < 28 mA Radio frequency 2402-2478 MHz Output power 0 dBm Table 4. Electrical Specifications PCB attributes Description PCB type 0.8mm 4 layer FR4 PCB dimension (length x width x height) 42mm x 16mm x 0.8mm Table 5. Physical Specifications Revision 1.0 Page 16 of 25
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Headset Reference Design v1.0 4 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. However, the radio module mounted on the headset can be used as- is together with the audio interfaces from the application board. Note: Most radio regulations do not allow more than 0dBm
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User Guide 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. Any replacement of this crystal must fulfill the crys- tal require
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Headset Reference Design v1.0 4.2 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. If you want an antenna redesign, any 50 ohm 2.4GHz antenna can be used, from an inexpensive PCB antenna to space saving chip antennas. There are different types of PCB antennas, from inverted F anten
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User Guide 5 Appendix 5.1 Bill Of Materials (BOM) Part Designator Footprint Description 10u C1 C3 C22 C27 SM/0805 Capacitor 0805/X5R/6V3/15% 10n C2 C4 C23 SM/0603 Capacitor 0603/X7R/50V/10% 4.7u C11 C14 SM/0603 Capacitor 0603/X5R/6.3V/10% 100p C16 C17 SM/0603 Capacitor 0603/NP0/50V/5% 2.2u C20 C21 C25 C26 SM/0603 Capacitor 0603/X5R/6.3V/10% 100n C24 SM/0603 Capacitor 0603/X7R/16V/10% SMA CJ1 TH/SMA Coax connector 85 SMA-50-0- 101 3.5mm CJ2 CJ3 TH/CON/K
