Audio PICtail™ Plus Daughter Board User’s Guide © 2007 Microchip Technology Inc.
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AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Table of Contents Preface ........................................................................................................................... 1 Chapter 1. Introduction 1.1 Overview ........................................................................................................ 7 1.2 Board Setup ................................................................................................... 8 1.3 Reference Documents ..........................
Audio PICtail™ Plus Daughter Board User’s Guide NOTES: DS70297A-page iv © 2007 Microchip Technology Inc.
AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Preface NOTICE TO CUSTOMERS All documentation becomes dated, and this manual is no exception. Microchip tools and documentation are constantly evolving to meet customer needs, so some actual dialogs and/or tool descriptions may differ from those in this document. Please refer to our web site (www.microchip.com) to obtain the latest documentation available. Documents are identified with a “DS” number.
Audio PICtail™ Plus Daughter Board User’s Guide CONVENTIONS USED IN THIS GUIDE This manual uses the following documentation conventions: DOCUMENTATION CONVENTIONS Description Arial font: Italic characters Represents Referenced books Emphasized text A window A dialog A menu selection A field name in a window or dialog A menu path MPLAB® IDE User’s Guide ...is the only compiler...
Preface WARRANTY REGISTRATION Please complete the enclosed Warranty Registration Card and mail it promptly. Sending in the Warranty Registration Card entitles you to receive new product updates. Interim software releases are available at the Microchip web site. RECOMMENDED READING This user's guide describes how to use Audio PICtail Plus Daughter Board. Other useful documents are listed below. The following Microchip documents are available and recommended as supplemental reference resources.
Audio PICtail™ Plus Daughter Board User’s Guide MPLAB® ASM30, MPLAB® LINK30 and Utilities User’s Guide (DS51317) This document helps you use Microchip Technology’s language tools for dsPIC33F DSC and PIC24H MCU devices based on GNU technology.
Preface DEVELOPMENT SYSTEMS CUSTOMER CHANGE NOTIFICATION SERVICE Microchip’s customer notification service helps keep customers current on Microchip products. Subscribers will receive e-mail notification whenever there are changes, updates, revisions or errata related to a specified product family or development tool of interest. To register, access the Microchip web site at www.microchip.com, click on Customer Change Notification and follow the registration instructions.
Audio PICtail™ Plus Daughter Board User’s Guide DOCUMENT REVISION HISTORY Revision A (October 2007) • Initial Release of this Document. DS70297A-page 6 © 2007 Microchip Technology Inc.
AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Chapter 1. Introduction Thank you for purchasing Microchip Technology’s Audio PICtail Plus Daughter Board. This board provides a low-cost interface for speech sampling and playback. The Audio PICtail Plus Daughter Board is used with the Explorer 16 Development Board to demonstrate an effective software technique for processing acceptable voice quality audio without the use of a codec device.
Audio PICtail™ Plus Daughter Board User’s Guide FIGURE 1-1: 1.2 AUDIO PICtail™ PLUS DAUGHTER BOARD BOARD SETUP Figure 1-2 is a photograph of Audio PICtail Plus Daughter Board plugged into Explorer 16 Development Board. A microphone and speaker are connected to the Audio PICtail Plus Daughter Board. The power supply and MPLAB ICD 2 are plugged into the Explorer 16 board.
Introduction 1.3 REFERENCE DOCUMENTS In addition to the Recommended Reading listed in the Preface, the following manufacturers’ data sheets are also recommended as reference sources: • National Semiconductor Corporation Data Sheet, LM4811 Boomer® Audio Power Amplifier Series Dual 105 mW Headphone Amplifier with Digital Volume Control and Shutdown Mode (DS200061) • Wolfson Microelectronics Data Sheet, WM8510 Mono CODEC with Speaker Driver, Production Data December 2006, Rev. 4.
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AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Chapter 2. Hardware This chapter provides a functional overview of the Audio PICtail Plus Daughter Board and identifies the major hardware components. Topics covered include: • Functional Overview • Hardware Components 2.1 FUNCTIONAL OVERVIEW The block diagram shown in Figure 2-1 illustrates the mainstream operation of the Audio PICtail Plus Daughter Board.
Audio PICtail™ Plus Daughter Board User’s Guide 2.1.2 Speech Playback The mainstream speech playback interface processes the pulse-width modulated digital signal from the Output Compare PWM module of the dsPIC33F or PIC24H device. A low-pass filter demodulates the PWM signal as shown in Figure 2-2. The low-pass filter behaves like an integrator whose output signal amplitude depends on the duty cycle of the input PWM waveform. The PWM frequency should be an integral multiple of the audio sampling rate.
H 2.1.5 a r d w a r e 4-Mb Serial Flash Memory The Audio PICtail Plus Daughter Board includes 4-Mb serial Flash memory that can be used for storing data. The memory interfaces with the SPI bus on dsPIC33F and PIC24H devices and might typically be used by applications that require storage of speech samples for playback purposes. 2.2 HARDWARE COMPONENTS Figure 2-3 identifies the key Audio PICtail Plus Daughter Board hardware components.
Audio PICtail™ Plus Daughter Board User’s Guide 2.2.1 Line/Microphone Input Phone Jack (J1) The Line/Microphone Input (Ref 4) is a 3.5 mm mono input phone jack (MJ3502). This connection accepts either a condenser microphone or a line level signal (see schematic in Figure A-2). 2.2.2 Line/Microphone Input Select Jumper (J8) The Line/Microphone Input Select Jumper (Ref 13) determines if the Microphone/Line Pre-Amplifier (U4:A) operates as a line amplifier or a microphone amplifier.
Hardware 2.2.7 PWM Low-Pass Filter (U3:A,B) The PWM signal from the Output Compare PWM module on the dsPIC33F or PIC24H device on the Explorer 16 board is demodulated by the PWM low-pass filter (Ref 6). This fourth order filter uses two of the four op amps (U3:A and U3:B) on the MCP6024 quad op amp IC. The input to the filter is selected by the Filter Input Select Jumper (J7). The output of the filter is routed to the headphone and line output amplifiers via the Output Select Jumper (J4).
Audio PICtail™ Plus Daughter Board User’s Guide 2.2.12 Line Output Jack (J9) Line out jack J9 (Ref 15) is a 3.5 mm stereo socket that can be used to connect the output of the line output amplifier to an external power amplifier or recording equipment. See Figure A-4 for a complete schematic of the Line Output Amplifier. 2.2.13 Headphone Amplifier (U5) The Headphone Amplifier (Ref 18) is a National Semiconductor LM4811 70 mW stereo amplifier with digital volume control.
Hardware 2.2.18 Codec Oscillator (Y1) Codec Oscillator Y1 (Ref 19) provides a required 12 MHz master clock signal to the 16-bit Codec (U2). See Figure A-5 for a complete schematic of the Codec. 2.2.19 Flash Memory (U1) The Audio PICtail Plus Daughter Board includes a serial Flash memory chip (Ref 2). This memory is write protected when the jumper pin is inserted in WP (Jumper J6). See Figure A-6 for a complete schematic of the Flash memory circuit. 2.2.
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AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Chapter 3. PWM Speech Loopback Demo This chapter describes a simple program that demonstrates how to use the Audio PICtail Plus Daughter Board for speech capture and loopback without the use of a codec. Topics covered include: • Speech Loopback Demo • Running the Demo 3.1 SPEECH LOOPBACK DEMO The CD that accompanies the Audio PICtail Plus Daughter Board contains a Speech Loopback Demo application.
Audio PICtail™ Plus Daughter Board User’s Guide The demo program consists of these basic software elements: • ADC Driver • Output Compare Module Driver • Loopback Application Software 3.1.1 ADC Driver The ADC driver reads the incoming signal on the specified 12-bit ADC channel (either AN0 or AN3), as determined by the ADC CH SEL jumper (J9). The driver interface is specified in the file ADCChannelDrv.h. The driver is implemented in ADCChannelDrv.c file.
PWM Speech Loopback Demo 3.1.3 Loopback Application Software The Loopback application on the accompanying CD uses the ADC and OCPWM drivers to read and output speech signals with the Audio PICtail Plus board. The application will loopback the microphone signal to the headphone output after performing a G.711 encode/decode operation on the microphone signal. Figure 3-2 is a flow chart of the demo application.
Audio PICtail™ Plus Daughter Board User’s Guide 3.2 RUNNING THE DEMO To run the demo, follow these basic steps: 1. Copy the demo programs from the Audio PICtail Plus Daughter Board CD to your MPLAB project folder. 2. With the Audio PICtail Plus Daughter Board plugged into the Explorer 16 Development Board, set up the Explorer 16 board to run with MPLAB IDE (using either MPLAB ICE or REAL ICE).
AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Appendix A. Drawings and Schematics This appendix provides detailed technical drawings and schematic diagrams of the Audio PICtail Plus Daughter Board. A.1 AUDIO PICtail PLUS DAUGHTER BOARD LAYOUT Figure A-1: Audio PICtail Plus Daughter Board Layout is a drawing of the Audio PICtail Plus Daughter Board layout. FIGURE A-1: A.
Audio PICtail™ Plus Daughter Board User’s Guide FIGURE A-2: SPEECH SAMPLING INTERFACE SCHEMATIC Line/Microphone Amplifier R29 C18 0.1 µF J8 U4:A J5 J1 MIC/SIG IN FIGURE A-3: ANTI-ALIASING LOW-PASS FILTER SCHEMATIC Anti-Aliasing Filter DS70297A-page 24 © 2007 Microchip Technology Inc.
Drawings and Schematics FIGURE A-4: SPEECH PLAYBACK INTERFACE SCHEMATIC PWM Low-Pass Filter FLT I/P SEL O/P SEL J4 Line Output Amplifier LINE OUT Headphone Amplifier HDPHONE CLK VOL UP/DN DAC Differential Amplifier © 2007 Microchip Technology Inc.
Audio PICtail™ Plus Daughter Board User’s Guide FIGURE A-5: CODEC SCHEMATIC C8 4.7 µF C6 4.7 µF C13 4.7 µF C10 4.7 µF C9 4.7 µF U2 DE-COUPLING CAPACITORS 2.2K FIGURE A-6: 2.2K FLASH MEMORY SCHEMATIC U1 DE-COUPLING CAPACITOR J6 WP DS70297A-page 26 © 2007 Microchip Technology Inc.
Drawings and Schematics FIGURE A-7: BOARD CONNECTORS Note: © 2007 Microchip Technology Inc. The 28-pin board must operate at +3.3V when it is connected to the Audio PICtail™ Plus Daughter Board.
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AUDIO PICtail™ PLUS DAUGHTER BOARD USER’S GUIDE Index A R ADC Driver ............................................................... 20 Reading, Recommended ........................................... 3 B S Bias Voltage ............................................................. 11 Board Connectors Schematic .................................. 27 Board Layout............................................................ 23 Schematic Diagrams ................................................
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