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march 2013 docid024106 rev 1 1/13 AN4227 application note audio hub demonstration kit supporting the mp45dt02, mp34db01, and mp34dt01 microphones introduction this document provides a brief description of the audio hub demonstration board steval- mki138v1 available from www.st.com along with simple steps to use the board with the apworkbench software tool. the purpose of this board is twofold: 1. it can be used as an stsmartvoice interface . in combination with this board (steval-mki126vx), it manages the signal coming from the onboard microphones. the stsmartvoice board hosts up to six microphones and the sta321mpl microphone processor converts the pdm signals from them into the common i 2 s audio format. (for additional details, please refe r to an4146 ?stsmartvoice demonstration board steval-mki126vx? available from www.st.com ). basically the audio hub, using the stm32f107rc microcontroller, is able to program the sta321mpl device via the i 2 c and decodes the i 2 s into a usb stream in order fo r the pc to manage the sound captured by the microphones. multiple f eatures for using the microphones on the stsmartvoice demonstration board are listed and accessible thanks to the apworkbench software tool. 2. it can be used as a usb sound card . as shown in figure 1 , the audio hub board hosts either the mp45dt02 or mp34dt01 (top-port digital microphones) and the mp34db01 which is a bottom-port digital microphone. the board is able to host both types of microphones as shown below. the task of th e stm32 microcontroller is to decode the pdm signals coming from the microphon es and stream the audio via the usb. figure 1. steval-mki138v1 entire board (top and bottom views) microphone section (zoom) mp45dt02 mp34dt01 mp34db01 www.st.com
contents AN4227 2/13 docid024106 rev 1 contents 1 hardware description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 software description (getting started wi th apworkbench) . . . . . . . . . . 6 2.1 stsmartvoice interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 usb voice recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 appendix a schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 appendix b layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
docid024106 rev 1 3/13 AN4227 hardware description 1 hardware description the connection is done through a usb cable th at supplies the board and also streams the audio collected by the microphones to the pc. figure 2. block diagram - microphone usb demonstration board referring to figure 2 : ? the supply section of the board is made up of one voltage regulator that steps down the 5 v of the usb connection to 3.3 v. the supply voltage ranges of the digital microphones are given below in table 1 . ? regarding the microphone sections, the mems outputs are a pdm signal, which is a high-frequency (1 to 3.25 mhz) stream of 1-bit digital samples. the ?functionality? section of each microphone datasheet (available on www.st.com ) provides details concerning the connections of the microphone in single channel configuration or stereo configuration by setting the lr pin. this pin sets the validity of the output data on the high level of the clock or on the low level as shown in table 2 . table 1. supply voltage range of microphones part number min. typ. max. mp45dt02 1.64 1.8 3.6 mp34db01 1.64 1.8 3.6 mp34dt01 1.64 1.8 3.6 table 2. l/r channel selection l/r clock low clock high gnd data valid high impedance vdd high impedance data valid sda scl lrck bick sdo12 sdo34 sdo56 stm32f107rc 12.288 mhz sel l/r clk vdd out gnd i2s spi i2c usb i/f l/r clk vdd out gnd sel regulator 3.3v 5v mic_vdd c_vdd usb connector 3.3v osc mic_vdd j1 j5 spi_ck st audio hub timer mic_ck mic_ck mic_data12 mic_vdd d1 d2 d3 d4 d5 mic_vdd mic_vdd c_vdd 12.288 mhz mclk sel mc o
hardware description AN4227 4/13 docid024106 rev 1 in this board the microphones are used in stereo configuration, so the two digital outputs are shorted (mic_data12, refer to schematic) and the two mems lr pins must be respectively set one to gnd and the other one to vdd. on the board, the resistors r1 and r13 already set the lr pin of the microphones, r1 and r42 give the user the poss ibility to change the mems polarity. note that the pcb sections hosting the mems microphones are detachable. this option has been considered to let the us er put the microphones in the desired position (i.e. for a display application in which the microphones are placed at the edges of the display). ? the hardware relative to the stm32f107rc microcontroller has been chosen to support both modes of usage listed above (either stsmartvoice interface or usb sound card). the board hosts two clock devices, the first one is a crystal quartz at 12.288 mhz and the other one is an active os cillator at 12.288 mhz as well. the first one, connected to the osc_in and osc_out pins, serves to gen erate the entire internal clock of the microcontroller (stm32 clock tree). once th e clock tree has been set, all the internal peripherals of the microcontroller have their own clocks. if the st audio hub is used as the stsmar tvoice interface, the internal clock tree provides the clock for the usb, for the i 2 c cell, for the i 2 s cell and also provides the clock for the daughterboard through the mco pin (12.288 mhz as well). the microcontroller is used to program the sta321mpl via i 2 c and also is used to decode the i 2 s coming from the daughterboard and to stream the audio via the usb. for this reason dedicated stm32 pins are connected to the connecto r physically interfacing the stsmartvoice board. an additional clock device (active oscillator) has been mounted for debugging purposes only. in the default configuration, the selector composed of r42, r21, and r17 is set to connect the mclk trace to the mco pin (refer to the schematic). if the st audio hub is used as a usb sound card, the clock tree is used to provide the mic_ck and spi_ck thanks to internal timers and a dedicated loop trace on the board (short between pin 21 and pin 27). the stm32 samples the output data of the microphones using the synchronous seri al port (spi1). the microphone signal mic_data12 is a stereophonic signal and the spi must be able to sample both channels. since mic_data12 is synchronous with its clock, spi_ck must be doubled. summarizing, the timer generates: ? mic_ck = 3.072 mhz ? spi_ck = 6.144 mhz the supported microcontroller usb interfac e allows streaming the audio on the usb peripheral, rendering this demonstration board compatible with any laptop or desktop.
docid024106 rev 1 5/13 AN4227 hardware description ? some leds have been mounted on the board, thus allowing a real-time check of what the demonstration board is performing. leds d1 and d5 give feedback about the supply and successful enumeration while the pu rpose of d2, d3 and d4 is to check the status of the board. d2 and d3 will alternat ely blink while the stm32 is in dfu mode (before the dedicated firmware has been corr ectly loaded into the flash memory of the microcontroller). checking the pc ?device manager? , the stm device in dfu mode will appear (see figure 3 below). figure 3. device manager when stm32 is in dfu mode the audio hub boards are provided by st with the firmware already loaded; the dfu section has been included to allow a firmware update by the user with no need for flash loader kits and is directly supported by the apw orkbench tool. the status of leds d1-d5 is summarized in the table below. table 3. led status d1 d2 d3 d4 d5 on: usb enumeration successful blinking: dfu mode off: firmware correctly downloaded blinking: dfu mode off: firmware correctly downloaded off: firmware correctly downloaded on: board supplied
software description (getting started with apworkbench) AN4227 6/13 docid024106 rev 1 2 software description (getting started with apworkbench) the firmware of the st audio hub supports two different audio frameworks. in the first case the board can be used as the interface for the stsmartvoice, allowing the i 2 c programming and the decoding of the i 2 s coming from the daughterboard. when the board is used for this purpose, it will be recognized as "staudiohub interface" (a) . the other possibility is the use of the board essentially as a pdm decoder that allows the couple of microphones on the board to be interfac ed directly to the pc via the u sb in which case the board will be recognized by the operative system as "stm32 capture pdm mode". the apworkbench tool allows choosing one of these modes by following these simple steps: 1. run the tool 2. click on the "mems microph ones demo kit" button 3. select the mode in the "microphone kit selection" box 4. click on the "run sele cted applicat ion?" button 2.1 stsmartvoice interface if the user wants to operate the board as the stsmartvoice interface, the corresponding mode must be selected as shown in figure 4 . figure 4. apworkbench launch wizard (stsmartvoice demonstration kit) a. apworkbench is compatible with wi ndows xp, windows vista and windows 7.
docid024106 rev 1 7/13 AN4227 software description (getting started with apworkbench) after this selection, the setup wizard panel of the stsmartvoice supported configurations will appear. for a detailed description of the meaning of the config urations listed in figure 5 , please refer to an4146 "stsmartvoice demons tration board steval-mki126vx" available on www.st.com . figure 5. stsmartvoice - setup wizard
software description (getting started with apworkbench) AN4227 8/13 docid024106 rev 1 2.2 usb voice recorder if the user wants to operate the board as a usb voice recorder, the proper mode must be selected as depicted in figure 6 . figure 6. apworkbench launch wiza rd (usb digital voice recorder) once this selection has been run, a dedicated panel will appear. if the user wants to operate the board as a usb voice recorder, the tool shows the panel performing either fft or scope monitoring. it is also possibl e to record the signal sensed by the microphones on the board. figure 7. usb voice recorder - fft monitoring
AN4227 schematics docid024106 rev 1 9/13 appendix a schematics figure 8. board schematic (power supply and jtag connector) c49 100nf 12 l3 inductor2 bead 1 2 d5 led-1 c41 10nf r38 1k c39 100nf + c40 33uf 12 l1 bead c5 100nf 1 2 r6 22 1 2 r12 22 1 2 r8 1.5k e b c q1 e b c q2 1 2 r22 36k 1 2 r23 10k 1 2 r24 1k 1 2 r25 47k 1 2 r26 180 1 2 d1 led-1 1 2 r27 0r0 nc 12 l4 bead 1 i/o1 2 gnd 3 i/o2 4 i/o2 5 vbus 6 i/o1 u8 usblc6-2 1 vbus 2 d- 3 d+ 4 id 5 gnd j7 mi ni typeb vout gnd vout vin 1 2 3 4 u4 ld1117 + c3 10uf 12 l6 bead vcc_usb vcc_usb a_vdd usbdm usbdp vcc_usb uc_vdd uc_vdd usb_disc mic_vdd 3.3v uc_vdd 1 2 r2 10k 1 2 r3 10k 1 2 r4 10k 1 2 r15 10k 1 2 3 4 5 6 7 8 9 10 j2 5x2_header 1 2 jp3 jp uc_vdd uc_vdd jtms stm32_i2s_bick stm32_i2s_lrck nrst jtck jrst
AN4227 schematics docid024106 rev 1 10/13 figure 9. board schematic (stm32 microcontroller, mangus ta option, clock generators, connectors, and microphones) 1 vbat 2 pc13-tamper-rtc 3 pc14-osc32_in 4 pc15-osc32_out 5 pd0_osc_in 6 pd1_osc_out 7 nrst 8 pc0 9 pc1 10 pc2 11 pc3 12 vssa 13 vdda 14 pa0-wkup 15 pa1 16 pa2 17 pa3 18 vss_4 19 vdd_4 20 pa4 21 pa5 22 pa6 23 pa7 24 pc4 25 pc5 26 pb0 27 pb1 28 pb2 29 pb10 30 pb11 31 vss_1 32 vdd_1 33 pb12 34 pb13 35 pb14 36 pb15 37 pc6 38 pc7 39 pc8 40 pc9 41 pa8 42 pa9 43 pa10 44 pa11 45 pa12 46 pa13 47 vss_2 48 vdd_2 49 pa14 50 pa15 51 pc10 52 pc11 53 pc12 54 pd2 55 pb3 56 pb4 57 pb5 58 pb6 59 pb7 60 boot0 61 pb8 62 pb9 63 vss_3 64 vdd_3 u5 stm32_lqfp64 1 2 r7 0r0 1 2 r9 0r0 1 2 r10 0r0 1 2 r11 0r0 c1 100nf 1 2 r5 10k c4 100nf 12 but1 tact2 12 34 56 78 910 11 12 13 14 15 16 j15 1 2 r19 100 1 2 r20 100 c6 ns c7 10pf c8 10pf 12 l2 820nh c9 100nf c10 10uf c11 100nf c12 4.7uf c13 100nf c14 4.7uf c15 100nf c16 4.7uf c17 100nf c18 4.7uf 1 gnd 2 lr 3 gnd 6 vdd 5 dout 4 clk u1 mp45dt01 c21 100nf c22 10uf 1 2 r29 100 c19 15pf c20 15pf 1 gnd 2 lr 3 gnd 6 vdd 5 dout 4 clk u2 mp45dt01 c23 100nf c24 10uf 1 2 r28 100 c25 15pf c26 15pf 1 2 r30 100 12 d2 led-1 1 2 r31 100 12 d3 led-1 1 2 r32 100 12 d4 led-1 r34 1k r35 1k 12 34 u3 xt_active 1 2 r37 10k c27 100nf 1 2 r33 10k 1 2 r36 0r0 1 2 r39 0r0 nc c28 2.2uf c29 2.2uf 12 l5 bead 1 2 3 4 j6 con4 1 2 3 4 j8 con4 1 2 3 4 j9 con4 1 2 3 4 j10 con4 tp1 spi1_cl ock c2 18pf c31 18pf tp2 tp3 1 2 r14 0r0 1 clk 5 gnd 3 vdd 4 data 2 l/r u7 mp34db01 1 clk 5 gnd 3 vdd 4 data 2 l/r u9 mp34db01 3 clk 4 data 2 l/r 1 vdd 5 gnd u10 mp34dt01 3 clk 4 data 2 l/r 1 vdd 5 gnd u11 mp34dt01 r16 0r ns 1 2 y1 12.288mhz 1 2 r17 0r 1 2 r18 0r r13 0r r42 0r ns r1 0r ns r41 0r 1 2 r21 0r ns 1 2 r40 0r ns i2s_bick i2s_lrck i2s_dat_12 i2s_dat_34 stm32_i2s_data34 stm32_i2s_data12 stm32_i2s_bick stm32_i2s_lrck uc_osc_in uc_osc_out uc_vdd uc_vdd scl sda nrst i2s_dat_12 i2s_dat_34 i2s_dat_56 i2s_bick i2s_lrck scl 3.3v reset stby sda mclk mute fail reset a_vdd uc_vdd uc_vdd mic_data12 uc_vdd mic_vdd mic_data12 mic_ck mic_vdd mic_data12 mic_ck led1 mic_ck led2 uc_vdd led1 led2 led3 uc_vdd uc_vdd uc_vdd stby mute fail uc_vdd 12.288_ck mic_vdd 12.288_ck led3 vss_cap vss_cap vss_cap 12.288_ck stm32_i2s_mclk mic_vdd mic_data12 mic_ck mic_vdd mic_data12 mic_ck stm32_i2s_lrck stm32_i2s_bick stm32_i2s_data12 stm32_i2s_mclk mco usb_disc usbdm usbdp jtms mco jtck jrst stm32_i2s_lrck stm32_i2s_bick stm32_i2s_data34 uc_osc_in uc_osc_out mic1ck mic1lr mic2ck mic_vdd mic_vdd mic1lr mic1ck mic_data12 mic_data12 mic_vdd mic_vdd mic_data12 mic2lr mic2ck stm32_i2s_mclk mco mic_vdd mic2lr
docid024106 rev 1 11/13 AN4227 layout appendix b layout figure 10. board layout - top view figure 11. board layout - bottom view
revision history AN4227 12/13 docid024106 rev 1 3 revision history table 4. document revision history date revision changes 22-mar-2013 1 initial release.
docid024106 rev 1 13/13 AN4227 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. st products are not authorized for use in weapons. nor are st products designed or authorized for use in: (a) safety critical applications such as life supporting, active implanted devices or systems with product functional safety requirements; (b) aeronautic applications; (c) automotive applications or environments, and/or (d) aerospace applications or environments. where st products are not designed for such use, the purchaser shall use products at purchaser?s sole risk, even if st has been informed in writing of such usage, unless a product is expressly designated by st as being intended for ?automotive, automotive safety or medical? industry domains according to st product design specifications. products formally escc, qml or jan qualified are deemed suitable for use in aerospace by the corresponding governmental agency. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2013 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - philippines - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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