Nordic Semiconductor NRD24V1 Manual de usuario
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Reproduction in whole or in part is prohibited without the prior written permission of the copyright holder.
February 2007
Headset Reference Design
nRD24V1
User Guide v1.0
Revision 1.0 Page 2 of 25
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. Nordic Semiconductor ASA cus-
tomers using or selling these products for use in such applications do so at their own risk and agree to fully
indemnify Nordic Semiconductor ASA for any damages resulting from such improper use or sale.
Contact details
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Revision History
Date Version Description
February 2007 1.0
Revision 1.0 Page 3 of 25
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.....................................................................................7
3.1.2 Micro controller.................................................................................8
3.1.3 Radio circuit .....................................................................................8
3.1.4 Antenna matching network...............................................................8
3.1.5 Power supply....................................................................................8
3.1.6 Programming....................................................................................8
3.1.7 Specifications...................................................................................9
3.2 Application board .................................................................................10
3.2.1 Audio interface.................................................................................10
3.2.2 Jumpers ...........................................................................................12
3.2.3 Antenna............................................................................................12
3.2.4 Power supply....................................................................................12
3.2.5 Buttons.............................................................................................13
3.2.6 Programming....................................................................................13
3.3 USB dongle..........................................................................................14
3.3.1 USB Interface...................................................................................15
3.3.2 Micro controller.................................................................................15
3.3.3 Radio circuit .....................................................................................15
3.3.4 Power supply....................................................................................15
3.3.5 Programming....................................................................................15
3.3.6 Specifications...................................................................................16
4 Hardware design guidelines........................................................................17
4.1 Headset................................................................................................17
4.1.1 Antenna............................................................................................17
4.1.2 Interfaces .........................................................................................17
4.1.3 Crystals............................................................................................18
4.1.4 MCU.................................................................................................18
4.1.5 Battery..............................................................................................18
4.2 USB dongle..........................................................................................19
4.2.1 Antenna............................................................................................19
4.2.2 MCU.................................................................................................19
4.2.3 Crystals............................................................................................19
5 Appendix.....................................................................................................20
5.1 Bill Of Materials (BOM) ........................................................................20
5.2 Application board schematics ..............................................................23
5.3 RF module schematics.........................................................................24
5.4 USB dongle schematics.......................................................................25
Revision 1.0 Page 4 of 25
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 dongle and two application boards with a radio module mounted. You can
establish a full duplex voice link between one application board and the USB dongle or between the two
application boards.
Target applications for the nRD24V1 are:
• Voice over IP headsets
• Short range intercom applications
•Toys
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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.
Figure 1. Headset unit with a USB configuration
Figure 2. System diagram of headset unit with USB configuration
Figure 3. ”Headset unit with an audio dongle configuration” and Figure 4. ”System diagram of headset unit
with audio dongle configuration” illustrate the headset unit with audio dongle configuration.
Figure 3. Headset unit with an audio dongle configuration
USB
dongle
Headset
unit
DAC
ADC
MCU
Voice
Protocol
I/O I/O PHY
RF
ShockBurst
Buttons LED
Application
Audio
Out
Audio
In
Application
MCU
Voice
Protocol
I/O
I/O
PHY
RF
ShockBurst
LED
I/O
USB
Audio Controller
USB USB
In/Out
Audio
dongle
Headset
unit
Revision 1.0 Page 6 of 25
User Guide
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 nRF24L01 uses the ShockBurst feature to transmit andreceive the RF packets in a time
multiplexed scheme. The micro controller fetches received 8-bit a-law samples from the nRF24L01, con-
verts to 16-bit linear PCM, and outputs to the audio codec. Button status is read by the MCU and embed-
ded in the RF packets.
The USB Dongle uses a USB Audio Controller to handle the USB interface. The audio samples are 16 bit
linear PCM between the USB Audio Controller and the micro controller, where the micro controller acts as
a bus master. The audio frame signals are derived from clock output from the USB Audio Controller to
keep the audio frames in sync with the USB audio frames. The micro controller can also access the USB
HID interface through the I2C bus, also with the micro controller as the bus master. The USB HID interface
is used to upstream button status received from the headset to the USB host. The micro controller converts
the 16 bit linear PCM code to an 8-bit a-law bit stream, which is sent to the nRF24L01 for wireless trans-
mission. The nRF24L01 uses the ShockBurst feature to transmit and receive the RF packets in a time mul-
tiplexed scheme.
DAC
ADC
MCU
Voice
Protocol
I/O
I/O
PHY
RF
ShockBurst
ButtonsLED
Application
Audio
Out
Audio
In
DAC
ADC
MCU
Voice
Protocol
I/O I/O PHY
RF
ShockBurst
Buttons LED
Application
Audio
Out
Audio
In
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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.
Figure 5. nRD24V1 radio module
3.1.1 Audio Codec
The audio codec is a XE3005 from Semtech that receives a 4.096 MHz master clock from the micro con-
troller. The micro controller configures the codec through the SPI interface. The 8 ksps audio samples are
transferred on the I2S interface, where the micro controller is the bus master.
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.
1 RF crystal 4 Audio codec
2 nRF24L01 5 MCU crystal
3MCU
1
2
3
5
4
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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 for driving. For example, this can be
used for an LED.
3.1.3 Radio circuit
The radio circuit (nRF24L01) is a complete radio transceiver for use in the unlicensed 2.4 GHz band. A 16
MHz crystal is used as a frequency reference for the RF. The RF output is matched to approximately 50
ohm at the antenna port. See section 3.1.4 ”Antenna matching network” below.
3.1.4 Antenna matching network
The RF output of the radio module is matched to approximately 50 ohm. An antenna is needed to set up
the RF link. There is a variety of different antenna types, please see section 4.1.1 ”Antenna” for more infor-
mation.
3.1.5 Power supply
The module needs a power supply in the range of 1.9 to 3.3 Volts. The module has been tested with a sup-
ply consisting of two ZinkAir cells (type 675) in series. Check the current consumption values shown in
Table 1. ”Electrical Specifications” below.
Note: Not all battery types are capable of handling the peak and average currents, even if the bat-
tery capacity is sufficient.
3.1.6 Programming
The module can be programmed using the ISP connector on the application board (see section 3.2 ”Appli-
cation board”), by connecting the appropriate pins on the module, or by using test probes on the corre-
sponding exposed vias on the back of the board.
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Headset Reference Design v1.0
3.1.7 Specifications
Table 1. Electrical Specifications
Table 2. Physical 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
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
Revision 1.0 Page 10 of 25
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.
Figure 6. Application board components
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.
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
6Switch6
4
5
7
8
10
11
3
1
2
6
9
Tabla de contenidos
