Microchip Technology AC164129 User Manuals

Table of Contents

• Introduction

  5
• Document Layout

  5
• Conventions Used in this Guide

  6
• Warranty Registration

  7
• Recommended Reading

  7
• The Microchip Web Site

  8
• Development Systems Customer Change Notification Service

  9
• Customer Support

  9
• Document Revision History

  10
• Chapter 1. Introduction

  11
• 1.1 Overview

  11
  • Figure 1-1: AUDIO PICtail™ PLUS DAUGHTER BOARD

    12
• 1.2 Board Setup

  12
  • Figure 1-2: AUDIO PICtail™ PLUS DAUGHTER BOARD Setup

    12
• 1.3 Reference Documents

  13
• Chapter 2. Hardware

  15
• 2.1 Functional Overview

  15
  • Figure 2-1: AUDIO PICtail™ PLUS DAUGHTER BOARD Block Diagram

    15
  • 2.1.1 Speech Sampling

    15
  • 2.1.2 Speech Playback

    16
    • Figure 2-2: PWM Demodulation

      16
  • 2.1.3 Codec

    16
  • 2.1.4 DAC Differential Amplifier

    16
  • 2.1.5 4-Mb Serial Flash Memory

    17
• 2.2 Hardware Components

  17
  • Figure 2-3: AUDIO PICtail™ PLUS DAUGHTER BOARD

    17
  • 2.2.1 Line/Microphone Input Phone Jack (J1)

    18
  • 2.2.2 Line/Microphone Input Select Jumper (J8)

    18
  • 2.2.3 Line/Microphone Pre-Amplifier (U4:A)

    18
    • Equation 2-1: Input Pre-Amplifier Gain

      18
  • 2.2.4 Anti-Aliasing Low-Pass Filter (U4:C)

    18
  • 2.2.5 Microphone Gain Control (R29)

    18
  • 2.2.6 ADC Channel Select Jumper (J5)

    18
  • 2.2.7 PWM Low-Pass Filter (U3:A,B)

    19
  • 2.2.8 Filter Input Select Jumper (J7)

    19
  • 2.2.9 Output Select Jumper (J4)

    19
  • 2.2.10 Line Output Amplifier (U4:B)

    19
    • Equation 2-2: Line Output Amplifier Gain

      19
  • 2.2.11 Line Output Gain Control Potentiometer (R24)

    19
  • 2.2.12 Line Output Jack (J9)

    20
  • 2.2.13 Headphone Amplifier (U5)

    20
  • 2.2.14 Headphone Amplifier Digital Volume Control

    20
  • 2.2.15 Headphone Output Jack (J10)

    20
  • 2.2.16 DAC Differential Amplifier (U3:C)

    20
  • 2.2.17 Codec (U2)

    20
  • 2.2.18 Codec Oscillator (Y1)

    21
  • 2.2.19 Flash Memory (U1)

    21
  • 2.2.20 Flash Memory Write-Protect Jumper (J6)

    21
  • 2.2.21 Explorer 16 PICtail Connector (J2)

    21
  • 2.2.22 28-Pin Starter Development Board Connector (J3)

    21
• Chapter 3. PWM Speech Loopback Demo

  23
• 3.1 Speech Loopback Demo

  23
  • Figure 3-1: Speech Loopback Demo Overview

    23
  • 3.1.1 ADC Driver

    24
  • 3.1.2 Output Compare Module Driver

    24
  • 3.1.3 Loopback Application Software

    25
    • Figure 3-2: Application Flow Chart

      25
• 3.2 Running the Demo

  26
• Appendix A. Drawings and Schematics

  27
• A.1 Audio PICtail Plus Daughter Board Layout

  27
  • Figure A-1: AUDIO PICtail™ PLUS DAUGHTER BOARD Layout

    27
• A.2 Schematic Diagrams

  27
  • Figure A-2: Speech Sampling Interface Schematic

    28
  • Figure A-3: Anti-Aliasing Low-Pass Filter Schematic

    28
  • Figure A-4: Speech Playback Interface Schematic

    29
  • Figure A-5: Codec Schematic

    30
  • Figure A-6: Flash Memory Schematic

    30
  • Figure A-7: Board Connectors

    31