Nordic Star Products NRD24V1 User's Manual
Contents
1. 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 e Voice over IP headsets e Short range intercom applications e Toys Revision 1 0 Page 4 of 25 Headset Reference Design v1 0 ON SEMIC DUCTO IR 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 d Headset unit Figure 1 Headset unit with a USB configuration Application Application Voice o Voice Protocol Figure 2 System diagram of headset unit with USB configuration Figure 3 Headset unit with an a2. 7 AOUTP Cp y 2QUIN AOUTN CP17 O A S AIN VREG11 VREG16 27 VREF VSSPA C10 C12 C11 R5 17 VSSA 10n I I pe VDD MCLK MOSI SCK SS SDO SDI FSYNC BCLK NRESET VSSD XE3005 VB RI 10 PDO RXD PD1 TXD C16 VB R3 10 C17 I 1 0n I VB R9 C1 100k 33n I L1 C6 C7 2 7n 4 7p I 2 2n I L2 8 2n L3 3 9n 0 9 R8 22k nRF24L01 da D lt wW o I N PD2 INTO MOSI PDS INT1 El TENE MISO 94 GN PD4 XCK CP8 PD5 KBDO cpi C9 1 5p CP10 C18 I pa CP9 Page 24 of 25 PD7 a O SEA KBD AREE ce TEMP m B LED CP16 RF module schematics 9 3 C14 I C5 I Y1 4 096MHz C2 I PC6 RESET PB7 XTAL2 ADC6 PB6 XTAL1 ATMega88 R6 DNM R7 DNM itle RFmodule Schematic Document Number SCH nRF24L01 VHR1 RM Thursday November 09 2006 ision 1 0 Rev O re gt O v D a D O E D Sn D d Sei D OC ml D U O o D L USB dongle schematics 9 4 3V3 3V3 3V3 C2 C1 C3 C4 C5 VUSB 10u 10n 10n 10n 10n o pui T ud 0 3V3 470n 2 2u R11 22k CODECSEL VDDOUT PADFUNO PADFUN1 PADFUN2 le 4 41 4 PADFUN3 Ml VOLDN vols De MUTEP Zi MUTER 232 HIDMUTER E SE RECORD GPioo HEC GPIO1 4 c11 C13 ends Lae da ile ila GPI03 20 3V3 Y XMCLK XSDO XSDIN ipd XLRCK i XSCLK dd 31 EE UE R3 o FREQMODE
3. 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 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 For your nearest dealer please see http www nordicsemi no Receive available updates automatically by subscribing to eNews from our homepage or check our web site regularly for any available updates Main office Otto Nielsen s vei 12 7004 Trondheim Phone 47 72 89 89 00 Fax 47 72 89 89 89 www nordicsemi no IDINIW AGCHELITATION hd No 03 NS EN ISO 9001 CERTIFICATED IRM Revision History February 2007 OO ae Revision
4. Do not exceed 3 6 V when using external voltage unless the linear regulator is used as this can damage the radio module Revision 1 0 Page 12 of 25 Headset Reference Design v1 0 ON DUCTOR SEMIC 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 as follows 1 If the unit has never been programmed set the AVR fuses Preserve EEPROM memory through chip erase cycle EESAVE 0 Brown out detection level at Vcc 1 8V BODLEVEL 110 e Clock output on PORT BO CKOUT 0 Ext Crystal Osc Frequency 3 0 8 0MHz CKSEL 1101 SUT 11 2 Write the SW hex file into the AVR program memory Write a 3 byte ID into the AVR EEprom The address should be written with the MSB at address 00 Revision 1 0 Page 13 of 25 SEMICONDUCTOR 3 3 USB dongle User Guide 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
5. 1 0 Page 2 of 25 Headset Reference Design v1 0 Contents 1 A 4 2 DY SIS MI SSC ONO n BEEN 5 3 Hardware description e 7 3 1 FIZ Vl FG MOOIE lean 7 3 1 1 ALO CON oran 7 3 1 2 MIST CON Ol Ponsa ones 8 3 1 3 Sree ee 8 3 1 4 Antenna matching Network i 8 9 1 5 POWCFSUPP E 8 3 1 6 FOr run ULe METRIS 8 3 1 7 DS CHCA ONS erotica ion to 9 3 2 ADDICQUOR see ase sets ns cpus utate aeter de Pee yu e 10 3 2 1 AUG Oe MC RACS cino 10 3 22 JUDO ni e 12 3 2 3 Antenn 12 3 2 4 PONErSUDP T m 12 3 2 5 BURON PP 13 3 2 6 41019162 140 01 e edo ote TM 13 3 3 JOB GONS nete ntt tekenden ennen dora 14 3 3 1 HSB INS AAPP 15 3 3 2 Wies mes gilde Ln 15 3 3 3 ROI A 15 3 3 4 POWSESUPP AAA PP UU UT 15 3 3 9 TODO ER NETTO TT 15 3 3 6 SPECIAL EN 16 4 Hardware design oudelmes A 17 4 1 A 17 4 1 1 e iau MM EIN 17 4 1 2 o T E 17 4 1 3 SL e eens seen 18 4 1 4 MODO 18 4 1 5 Battery E 18 4 2 USB COIS ERIT enen eenden 19 4 2 1 e AA 19 4 2 2 jeu 19 4 2 3 Ss eege 19 9 AA e E O E 20 5 1 BIO Materials BOM scsi 20 5 2 Application board schematics sese eee eee 23 5 3 REMOUS CNE er 24 5 4 USB dongle schematics eee 25 Revision 1 0 Page 3 of 25 D User Guide SEMICONDUCTOR 1 Introduction
6. Using a chip antenna must only be done according to the chip antenna vendors recommendations The USB Dongle is equipped with the recommended antenna matching network layout for the nRF24L01 and a PCB quarter wave antenna If a different antenna Is going to be used it is important to tune the antenna matching network to match the impedance at the antenna s terminal Another important task of the antenna matching network is to Suppress spurious energy This can be achieved by following our White Paper named Tuning the nFR24xx matching network available on our website www nordicsemi no 4 2 2 MCU A replacement of the MCU must fulfill these requirements e 8 bit MCU e 6 MHz clock frequency e 1 to 2 cycles per instruction e 4bytes E2PROM Memory can be external e kbyte of IRAM can maybe work with 512kbytes e 8kbyte program memory possible to get down to 5 to 6kbytes e One Double buffered synchronous hardware SPI both on RX and TX or Ideally 12S interface e One SPI port for RF and codec e One two wire interface to USB Audio Controller for call control open drain type e Watchdog times for power management e One 16 bit timer Master sync clock e One 8 bit timer hardware sync clock e 1 9 to 3 6V supply voltage 4 2 3 Crystals The crystal used as the RF crystal is a 16 MHz crystal Any replacement of this crystal must fulfill the crys tal requirements found in the nRF24L01 Product Specification The MCU crystal fulfills the
7. requirements given by the MCU The frequency must be 6 0 MHz in order to get the timing correct Any replacements must follow these requirements Revision 1 0 Page 19 of 25 SEMICONDUCTOR User Guide 5 Appendix 5 1 Bill Of Materials BOM SMA CJ1 TH SMA ME Coax connector 85 SMA 50 0 1 01 R pi 0603D LED RedEL19 21VRO 470u L1 L5 SM 1210 Inductor Bor tes D ON nRF24L01 VoIP Appli PCB1 PCB Paton Board NPN BC847BL R4 Rb ARS R6 R7 SM 0603 Resistor 0 1W 0603 1 R8 R9 R12 SM 0603 Resistor 0 1W 0603 1 R13R16R17R18 SM 0603 Resistor 0 1W 0603 1 R25 SW6x6 SW1 SW2 SW3 SW4 SM SW 6x6 Switch TACT B351000 SW5 SPDT SW6 SW7 SW8 TH SW OS1020 Switch Mechanical OS102011MS2QN1 nRF24L01 VHR1 RM U1 WHS nRF24L01 Radio Module nRF24L01 VHR1 RM LP2985AIM5 2 5 SM SOT23 5 Linear Regulator LP2985AIM5 2 5 ane w JPINPROWILUS Pinton 8254872 dumperzsimm WA WWW Jumper 2 8mm M7585085 One in each corner Rubber Feel under the board Table 6 Application board BOM Revision 1 0 Page 20 of 25 Headset Reference Design v1 0 SEMICONDUCTO AJ On ClC8C4C5C6CIi SM 0402 Capacitor 0402 X7R 16V 10 47u C23 CAPMP3528X210L Capacitor Tant B TTT Ei 4 7n L1 SM 0402 Inductor RF lee E 8 2n L2 SM 0402 Inductor RF TT V i iesen 5 6n L3 SM 0402 Inductor RF LQP15MN5N6B02D USB A CON USB A PLUG USB connector
8. 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 requirements found in the nRF24L01 Product Specification The MCU crystal fulfills the requirements given by the MCU The frequency must be 4 096MHz in order to get the timing correct Any replacements must follow these requirements 4 1 4 MCU It is important that the MCU has a double buffered SPI in both the TX and RX direction because the MCU handles the audio stream and requires it to be continuous A replacement of the MCU must fulfill these requirements e 8 bit MCU e 4 096 MHz clock frequency e 1 to 2 cycles per instruction e 4bytes E2PROM Memory can be external e kbyte of IRAM can maybe work with 512kbytes e 8kbyte program memory possible to get down to 5 to 6kbytes e One Double buffered synchronous hardware SPI both on RX and TX or Ideally 12S interface e One SPI port for RF and codec e Watchdog times for power management e One 16 bit timer Master sync clock One 8 bit timer hardware sync clock e 1 9 to 3 6V supply voltage 4 1 5 Battery The batteries included in the reference design kit are of the type Zink Air Zn size 675 Two batteries of this size are connected in series to achieve the supply voltage needed Any battery that can supply a voltage between 1
9. v1 0 SEMICONDUCTOR 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 OdBm output power without doing proper fre quency hopping Adding a PA to this design requires a major re design of the radio protocol because the headset reference design uses a frequency agility protocol 4 1 Headset The radio module is used as is in the headset design but it must be interfaced in a way that ensures opti mal performance 4 1 1 Antenna The radio module is connected to the antenna on the application board This antenna does not fit into a headset design for a finished product so using the radio module in a headset application for a finished product will require a different type of antenna In a headset application for a finished product the radio module must be mounted on a PCB with an antenna terminal On this antenna terminal any 50 ohm 2 4GHz antenna can be used from an inexpen sive PCB antenna to space saving chip antennas There are different types of PCB antennas from inverted F antennas to simple quarter wave antennas You must know
10. 1 FREQMODE2 SDA SCL LEDN RSTN PDSW VSSA_PLLA VSSA_PLLB VSS SN11220ACF 3V3 i 6 0MHz R20 470 C17 C18 22p 22p a d D E G Q1 PDTC115TU PDO RXD PD1 TXD PD2 INTO PD3 INT1 PD4 XCK PD5 PD6 PD7 AREF PB7 XTAL2 PB6 XTAL1 PBO CLKO PB1 PB2 SS PB3 MOSI PB4 MISO PB5 SCK PCO PC1 PC2 PC3 PC4 SDA PC5 SCL PC6 RESET ADC6 ADC7 ATMega88 nRF24L01 VoIP USB Dongle Board C6 C7 T 1 0n I L1 2 7n Q nRF24L01 RGE L 1 R 16MHz C16 C15 itle USB Dongle SCHEMATIC1 Document Number SCH nRF24L01 VHR1 UD Thursday November 23 2006 C9 C10 4 7p il 2 2n I L2 8 2n L3 C12 C26 3 9n 1 5p 1 0p A1 1 0p Ri 1 22k Page 25 of 25 ision 1 0 Rev
11. 1 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 Connecting to Connect to headset Connect to headset Mount jumpers 4 Mount jumper 2 headset microphone loudspeaker and 5 Connecting to PC Connect to PC micro Connect to PC loud Mount jumpers 1 Mount jumper 1 phone input speaker output 2 and 3 Table 3 Audio filter settings 3 2 3 Antenna The RF output of the radio module is matched to approximately 50 ohm An antenna must be connected to the SMA connector to set up an RF link 3 2 4 Power supply The application board is fitted with two coin cell battery holders connected in series for use with ZinkAir type 675 batteries The board also contains a footprint for a CR2 Li battery holder 1 2 AA Bulgin BX0031 Alternatively an external power supply can be connected to P3 You select battery or external voltage with SW6 The voltage supply to the RF module should be between 1 9 and 3 6 V If the onboard 2 5 V linear regula tor is used the input voltage should be between 3 and 15 V The linear regulator can be switched on or bypassed with SW7 and SW8 both switches should have the same position Note
12. 48037 2100 nRF24L01 VolP USB PCB1 PCB aea gang PDTC115TU Q1 SM SOT323 NPN with resistors TT TT ewen 0 R8RSR2iR26 Sum Resistor 0 1W 0402 1 TEK SN11220ACF U1 TSQFP50P900X900X16 USB Audio Controller ATMega88 U3 QFN50P500X500X100 Microcontroller ATmega88V 33AL 10MU 93C46 SSOP 8 EEPROM 1k AT93C46 10TU 2 7 16MHz W42 5 Crystal TSX 10 16MHz 6 0MHz H XO CA 301 Crystal CA 301 6 000M C Connector P3 ISP Connector BMO6B SRSS TB LF SN Table 7 USB dongle BOM Revision 1 0 Page 21 of 25 User Guide An nRF24L01 VoIP PCB1 SC On NN 6 10 RS 1M R4 SMi0402 Resistor O 1W 0402 1 22k R8 SM 0402 Resistor 0 1W 0402 1 i 22k XE3005 ITSSOP 20 Audio Codec XE30051033TRLF ATMega88 U3 SCS ORE Microcontroller Aglo oO 100 33AL 10MU nRF24L01 QFN20 4X4 HF Transceiver nRF24L01 4 096MHz THXOCASUL 301 Crystal EEL CSASOS LOSEMIABTUB 4 096MABJ UB 16MHz XW4 2 5 Crystal TSX 10 16MHz Table 8 Radio module BOM Revision 1 0 Page 22 of 25 Headset Reference Design v1 0 5 2 Application board schematics 73 00mm N o H IR 19 319 El Kl La E E B R22 kl E tn u NI IS RIE O cy N jJ lo wwoo LS aT IL 900Z TT 60 2320 48qunN JU3SWN20 burmesg A quassy gU IHH TO Tv Z JHU WSU p4eog uor3je2r ddg Revision 1 0 Page 23 of 25 El al 0 9 O Sn D GA VDDPA eps y AOUTP
13. 9V and 3 6V and sustain the peak current of 15mA can be used in this application You can calculate the battery lifetime in both talk time and standby time from the average current con sumption At Vdd 3V the average current consumption in connect mode is 7mA and the average current consumption in idle mode is 250uA At Vdd 2V they are 5 7V and 230A respectively A battery with capacity 630mAh like the Zn 675 will have the following battery lifetime Talk time 630mAh 7mA 90h e Standby time 630mMAh 250uA 2520h The figures for Vdd 3V are used because the two batteries in series have a nominal output voltage of 2 8V Revision 1 0 Page 18 of 25 ORD SEMICONDUCTOR 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 antennas to simple quarter wave antennas You must know the characteristics of the chosen antenna and implement it as required Tuning the antenna will be necessary because an antenna s impedance and performance are affected by the environ ment the antenna is used in
14. B 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 Revision 1 0 Page 6 of 25 Headset Reference Design v1 0 SEMICONDUCTOR 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 GPIOSs 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 1 6019 CG C 5 DO c D a o 9 J 2 1 HF crystal 4 Audio codec 2 nRF24L01 5 MCUcrystal 3 MCU 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 Th
15. both sides of the board 4 1 MCU 3 nRF24L01 2 MCU crystal 4 RF crystal Figure 11 nRD24V1 USB dongle top side QD Z C4 4 T LL me Titi etl eee USB MCU 3 ISP connector EE Prom 4 2 Figure 12 nRD24V1 USB dongle bottom side Revision 1 0 Page 14 of 25 Headset Reference Design v1 0 SEMICONDUCTOR 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 125 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 The micro controller can also access the USB HID interface through the 12C bus also with the micro controller as the bus master 3 3 2 Micro controller The micro controller is an AVR ATmega88 that runs on a 6 00 MHz crystal The micro controller s main tasks are Setting up USB controller and radio circuits e Converting 16 bit PCM audio samples from the USB controller to 8 bit a law samples for the radio circuit e Converting 8 bit a law samples from the radio circuit to 16 bit linear PCM e Handling the RF protocol e Optional HID interface for communication with PC application In addition an LED output is available The LED will light up when USB aud
16. e 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 Revision 1 0 Page 8 of 25 Headset Reference Design v1 0 3 1 7 Specifications Supply voltage IEN Current consumption Idle lt 1 mA average 15 mA peak at 2 5 V supply Connected lt 7 mA average 15 mA peak at 2 5 V supply Radio frequency 2402 2478 MHz Output power loden Table 1 Electrical Specifications 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 of 25 NORDIC SEMICONDUCTOR User Guide 3 2 Application board The nRF24L01 VHH1 application board contains all peripherals necessary to build a complete audio mod ule from the nRF24L01 VHH1 radio module 7 1 8 2 9 3 4 10 5 11 1 Radio module 7 P8 external power 2 Linear regulator 8 Batteries 3 Jumpers 9 Switches 7 and 8 4 Audio interface 10 ISP programming 5 Jumpers 11 Buttons 6 Switch 6 Figure 6 Application board components 3 2 1 Audio interface This module can be used to set
17. e loudspeaker outputs are a differential class D output and need some external filtering components Revision 1 0 Page 7 of 25 D User Guide SEMICONDUCTOR 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 e Converting 8 bit a law samples from the radio circuit to 16 bit linear PCM e 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 Tabl
18. io activity is present on the USB port 3 3 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 frequency reference for the RF and an antenna is included in the layout 3 3 4 Power supply The USB dongle is powered from the USB port and needs no extra supply 3 3 5 Programming A 6 pin ISP connector is available on the back of the PCB The included ISP cable can be used to connect this connector to an AVR programming tool like the STK500 from Atmel The programming procedure is as follows 1 If the unit has never been programmed set the AVR fuses Preserve EEPROM memory through chip erase cycle EESAVE 0 e Brown out detection level at Vcc 2 7V BODLEVEL 101 e Ext Full swing Crystal CKSEL 0111 SUT 01 2 Write the SW hex file into the AVR program memory 3 Write a 3 byte ID into the AVR EEprom The address should be written with the MSB at address 00 Revision 1 0 Page 15 of 25 SEMI User Guide 3 3 6 Specifications Supply voltage J 45 58V O O Oo o Current consumption Idle lt 2AMA O Connected 28mA Radiofrequency 240224 8MHz O Output power OB Table 4 Electrical Specifications 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 ORD Headset Reference Design
19. the characteristics of the chosen antenna and implement it as required Tuning the antenna will be necessary because an antennas impedance and performance is affected by the environ ment the antenna is used in Using a chip antenna must only be done according to the chip antenna vendors recommendations The radio module is equipped with the recommended antenna matching network layout for the nRF24L01 When operating from the application board the radio module s antenna matching network is tuned to match the application board antenna impedance When using the radio module in a headset application for a finished product it is important to tune the antenna matching network to match the impedance at the antenna s terminal Another important task of the antenna matching network is to Suppress spurious energy You can achieve this by following our white paper called Tuning the nFR24xx matching network available on our website www nordicsemi no 4 1 2 Interfaces 4 1 2 1 Buttons Any active closed push buttons referring to ground can be used because the MCU used on the radio mod ule has internal pull up resistors on the button input signals The radio module can handle up to five but tons Revision 1 0 Page 17 of 25 D User Guide SEMICONDUCTOR 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
20. udio dongle configuration and Figure 4 System diagram of headset unit with audio dongle configuration illustrate the headset unit with audio dongle configuration ST Headset Audio unit dongle Figure 3 Headset unit with an audio dongle configuration Revision 1 0 Page 5 of 25 User Guide Application Voice Protocol 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 and receive 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 US
21. 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 Revision 1 0 Page 10 of 25 SEMICONDUCTOR 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 Figure 7 Loudspeaker interface 3 2 1 2 PC interface The differential loudspeaker output from the codec must be connected single ended to the PC microphone input and the PC loudspeaker output must be connected to the codec microphone input to interface with a PC audio port Figure 8 PC input interface shows the networks that accommodate this The loudspeaker output from the PC must be level adjusted and a network as shown in Figure 9 PC output interface used C1 R1 L1 56 470u C8 AOUTP C7 i 2 2U l 100n gt PC microphone input C2 C3 V Figure 8 PC input interface Revision 1 0 Page 11 of 25 D User Guide SEMICONDUCTOR C
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