WT32i REFERENCE DESIGN

Transcription

1 WTi REFERENCE DESIGN APPLICATION NOTE Monday, February 0 Version 0.

2 Copyright Bluegiga Technologies All rights reserved. Bluegiga Technologies assumes no responsibility for any errors which may appear in this manual. Furthermore, Bluegiga Technologies reserves the right to alter the hardware, software, and/or specifications detailed here at any time without notice and does not make any commitment to update the information contained here. Bluegiga s products are not authorized for use as critical components in life support devices or systems. The WRAP is a registered trademark of Bluegiga Technologies The Bluetooth trademark is owned by the Bluetooth SIG Inc., USA and is licensed to Bluegiga Technologies. All other trademarks listed herein are owned by their respective owners.

3 VERSION HISTORY Version Comment 0. First draft 0. Minor improvements

4 TABLE OF CONTENTS Introduction... Hardware Design of DKWTi v..... Choosing the Capacitors and Resistors Used in the Audio Path.... How to Avoid Pops and Cracks When Powering the Board or Establishing ADP connection...7. Schematic and Assembly of DKWTi v Layout of DKWTi.... RF, EMC and Audio Layout Considerations... 7 Example iwrap Configuration Setting iwrap for Headset Use... 9 Contact Information...

5 Introduction This documents describes detailed the design of WTi development kit. Page of

6 Hardware Design of DKWTi v.. Choosing the Capacitors and Resistors Used in the Audio Path Metal film resistors have lower noise than carbon resistors which makes them more suitable for high quality audio. Non-linearity of capacitors within the audio path will have an impact on the audio quality at the frequencies where the impedance of the capacitors become dominant. At higher frequencies the amplitude is not determined by the value of the capacitors, but at the lower frequencies the impact of the capacitors will be seen. Ceramic capacitors should be XR or X7R type capacitors with relative high voltage rating. The higher the capacitance value, the lower is the frequency where the non-linearity will start to have an impact. Thus it is not a bad idea to select the capacitors value bigger than necessary from the frequency response point of view. For optimal audio quality the best selection is to use film capacitors. Film capacitors have excellent linearity and they are non-polarized which makes them perfect choice for using in audio path. The drawback of film capacitors is bigger physical size and higher cost. Figure shows a modulation distortion measurement when using different type of capacitors in the audio paths. Modulation distortion measures the amount of distortion between two closely located sine waves. The difference between the different capacitors is obvious at low frequencies where the impedance of the capacitor is dominant. Figure : Intermodulation distortion with different type of capacitors Page of

7 . How to Avoid Pops and Cracks When Powering the Board or Establishing ADP connection Figure : Extenal audio PA connection To match the impedances Z and Z it is important that the capacitors at the input of the amplifier are well matched together. The tolerance of a ceramic chip capacitor is typically in the range of % - 0% and generally ceramic capacitors are more accurate than film capacitors. Thus in this case ceramic X7R capacitors with % tolerance were chosen for the external audio PA to minimize the pop sound when the ADP link is established or switched off. Page 7 of

8 Figure : Equivalent circuit for simulating the transient caused by the impedance mismatch Page 8 of

9 . Schematic and Assembly of DKWTi v. Figure : DKWTi v. Schematic (/) Page 9 of

10 7 X S H OR TIN G_LIN K J-9J-0 V B U S J L kohm@00mhz, DC 0.ohm D 7 D IO/SC H OTTKY/MBR A0/A/0V R K, 0V, 0.0W, +/-% R.K, 0V, 0.0W, +/-% P IO8/U S B _D E T D - G ID D +D -V U USBLC- D + R 8.K, 0V, 0.0W, +/-% P IO/U S B _P U LL-U P U and U7 disconnect UART converter when the cable is not plugged J G ID D +D -V L kohm@00mhz, DC 0.ohm D D IO/SC H OTTKY/MBR A0/A/0V U USBLC- R.K, 0V, 0.0W, +/-% C 0 R 7 7R, 0V, 0.0W, % R 7R, 0V, 0.0W, %.uf/0v/xr /0% 0VDD_ D+ D- GP0 GP PLL_TEST 7 OSC 8 OSC U PL0HX G N D _A LDO v USB to UART G N D G N D G N D 8 C VO_ VDD_ TXD RXD RTS CTS DTR DSR RI DCD SHTD NC NC NC.uF/0V/XR /0% EE_CLK EE_DATA 8 9 R C.K, 0V, 0.0W, +/-% 0.uF/0V/XR /0% R 0K, 0V, 0.0W, +/-% 7 U7 7AUPG V 8 8 V 7 U 7AUPG U A R T_TX U A R T_R TS U A R T_R X U A R T_C TS Figure : DKWTi v. Schematic (/) Page 0 of

11 Figure : DKWTi v. Schematic (/) Page of

12 U R C A _R E D U R C A _W H ITE TIP R IN G Mohm resistors set the DC level to GND preventing pop sound when plugging in the audio connector Voltage divider to limit the line amplitude below Vpp J S J--S MT-TR S LE E V E MIC_B IA S M, 0V, 0.W, % R XR, X7R or Film type DC block capacitors. The input impedance is in the range of kohm...0kohm depending on the gain settings. The cut off frequency is /(Pi*R*C) M, 0V, 0.W, % R R 7.K, 0.0W, 0.% C7.uF /0V /X R/0% R 0R0, 0V,.0A, 0.W S LE E V E R IN G R NP R 0R0, 0V,.0A, 0.W R8 7.K, 0.0W, 0.% R7 0R0, 0V,.0A, 0.W S W S W_S LIDE _LS S A M-V J S W L nh+/-%, 00mA L nh+/-%, 00mA L nh+/-%, 00mA L nh+/-%, 00mA C pf/0v /C0G/% C pf/0v /C0G/% C pf/0v /C0G/% R9 R0.K, 0.0W, 0.%.K, 0.0W, 0.% C uf/v /0% C7 uf/v /0% C8 uf/v /0% C9 A _IN_LE FT_N A _IN_LE FT_P A _IN_RIGHT_N R IN G_S W TIP _S W NP R7 S W_S LIDE _LS S A M-V C pf/0v /C0G/% uf/v /0% A _IN_RIGHT_P TIP J C ON _JA C K _S W _S J--S MT-TR R K, 0V, 0.0W U LC filtering to prevent RF noise travelling to audio input MIC _W M70A True Preload resistor for the microphone. Figure 7: DKWTi v. Schematic (/) Page of

13 8 9 V Software IC interface to configure the IS codec R 7.K, 0V, 0.0W, +/-% V D D MR R S T V S S R S T R E S E T PIO/IC _SC L PIO7/IC _SD A IS_SC K IS_WS IS_SD IN IS_SD OU T U 0 MC P 9 A B A B S W V R 8 J.7K, 0V, 0.0W, % R 0.7K, 0V, 0.0W, % V U M, 0V, 0.W, % R C A _R E D U 8 R C A _W H ITE TIP R IN G R 9 M, 0V, 0.W, % R C uf/v /0% C uf/v /0% SC L SD A MIC B IA S 0 MIC L/LIN E L MIC L/LIN E L MIC R /LIN E R MIC L/LIN E L MIC R /LIN E R MIC R /LIN E R R ESET MC LK BC LK WC LK D OU T D IN A V D D _D A C 8 D R V D D D R V D D 7 IOV D D D V D D D V S S 7 A V S S _A D C A V S S _D A C D R V S S 0.uF/0V/XR /0% 0.uF/0V/XR /0% C C C C uf/.v/xr /0% uf/.v/xr /0% 0.uF/0V/XR /0% 0.uF/0V/XR /0% C 8 C 9 C C uf/.v/xr /0% C 0 uf/.v/xr /0% 0uF/.V/XR /0% 0.uF/0V/XR /0% C C uf/.v/xr /0% S LE E V E J0 S J--S MT-TR J7 C 0 uf/v /0% C 9 uf/v /0% H PR OU T 9 H PLOU T 0 H PLC OM H PR C OM R IGH T_LOP 9 0 R IGH T_LOM 7 LEFT_LOP 8 LEFT_LOM GN D GN D GN D GN D U 9 TLV 0A IC C uf/.v/xr /0% OU T U 8 A P 7 GN D IN C uf/.v/xr /0% U R C A _R E D R M, 0V, 0.W, % C R 7 0.uF/0V/XR /0% N P J8 C 0uF/.V /0% /TA N /E S R <0mohm U R C A _W H ITE C 0uF/.V /0% /TA N /E S R <0mohm TIP R IN G S LE E V E J8 S J--S MT-TR R M, 0V, 0.W, % C R N P 0.uF/0V/XR /0% J9 Figure 8: DKWTi v. Schematic (/) Page of

14 Figure 9: WTi Development Board Assembly Drawing Page of

15 . Layout of DKWTi Figure 0: Top layer layout of DKWTi contains signal and audio tracing Figure : nd layer layout of DKWTi contains a solid GND plane Page of

16 Figure : rd layer layout of DKWTi contains supply voltages Figure : Bottom layer layout of DKWTi contains GND and signal tracing Page of

17 . RF, EMC and Audio Layout Considerations GND vias are placed right next to any GND pad to connect GND pads directly to the solid GND plane. This is to make sure that the return current path is low impedance without any loops. GND planes are stitched with vias at the edges Of the PCB to prevent emissions Figure : GND vias in DKWTi Differential audio signals are traced parallel to make sure they have perfect common mode rejection. All the audio traces are routed on a solid GND plane. Figure : Routing of differential audio signals Page 7 of

18 GND plane is required on both sides of the Antenna. The antenna uses the GND plane as a part of radiator and the lack of GND plane will signifficantly reduce the performance. Metal clearance area under the antenna. Antenna placed at the edge of the PCB. Figure : Clearance area under the antenna Page 8 of

19 Example iwrap Configuration. Setting iwrap for Headset Use Plug USB cable to the USB connector labeled UART, set the power switch to the USB position and connect to DKWTi with a terminal program such as Putty. Type SET to see the default configuration of WTi. Following steps demonstrate an example iwrap configuration for a headset use (refer to the iwrap user manual for details):. Set the friendly name for the device so it is easily discoverable Type: SET BT NAME DKWTi. Set the Bluetooth Class-of-Device (CoD). Class of device is a parameter, which is received during the device discovery procedure, indicating the type of device and which services are supported. The hexa number describing the class of device can be generated with a class of device generator which can be found here: Type: SET BT CLASS 08. Set the page mode. Page mode controls whether iwrap can be seen in the inquiry and whether it can be connected. The default is visible when not connected and not visible when connected. Type: SET BT PAGEMODE 000. Set the audio routing to either through the internal or external codec. The default is internal. Type: SET CONTROL AUDIO INTERNAL INTERNAL. Set the ADP codec priorities (SBC, aptx or AAC) Type: SET CONTROL CODEC SBC JOINT_STEREO 00 (These command set SBC first in the priority list. Apt-X license is not delivered by default in WTi. To enable Apt-X codec, type SET CONTROL APT-X JOINT_STEREO 00 X, where X is the priority. Note that the caller end of the BT link will decide which codec is to be used. Thus if Apt-X is enabled and phone with Apt-X calls to WTi, Apt-X codec will be used despite of if it is lower in priority than SBC). Enable the desired BT profiles. For headset the relevant profiles are HFP, ADP and AVRCP. Type: SET PROFILE ADP SINK SET PROFILE HFP ON SET PROFILE AVRCP CONTOLLER 7. Set the pairing code Type: SET BT AUTH * Configure the volume up and volume down buttons Type: SET CONTROL BIND 0 00 R VOLUME DOWN Type: SET CONTROL BIND 00 R VOLUME UP Type: SET CONTROL BIND 8 R AVRCP PLAY Type: SET CONTROL BIND R AVRCP PAUSE These command set PIO9 as volume down button, PIO0 as volume up button, PIO as play button and PIO0 as pause button. Page 9 of

20 9. Configure carrier detect signal to indicate active connection Type: SET CONTROL CD 0 0 This command will drive PIO high when there is an active connection. In the DKWTi the LED connected to PIO will lit. 0. Configure the on/off button. to turn the power on at the rising edge and turn off at the following rising edge Type: SET CONTROL VREGEN This configures the VREG_EN pin to latch the power on at the rising edge and turn off at the following rising edge. PIO is used to control the external regulator on.. Configure the module to indicate low battery voltage by driving PIO8 high when the battery voltage falls below.v and to turn off the power when the battery voltage falls below.0v. PIO8 is driven low when the battery voltage exceeds.0v. Type: SET CONTROL BATTERY Page 0 of

21 Contact Information Sales: Technical support: Orders: Web site: Head Office / Finland: Postal address / Finland: Sales Office / USA: Sales Office / Hong-Kong: Phone: Fax: Sinikalliontie A 00 ESPOO FINLAND P.O. BOX 0 0 ESPOO FINLAND Phone: Fax: Bluegiga Technologies, Inc. Satellite Boulevard, Building 00, Suite 00 Duluth, GA, 009, USA Elite Business Center /F, Millenium City 70 Kwun Tong Road Kwun Tong Kowloon Hong Kong Page of