ALINX AN831 WM8731 Audio Capture Module User Manual

1. Introduction

The ALINX AN831 is a compact audio capture module designed for high-quality analog-to-digital (A/D) and digital-to-analog (D/A) conversion of audio signals. Featuring the WM8731 audio codec chip, this module provides essential audio input and output interfaces, making it an ideal peripheral for FPGA development boards and other embedded systems requiring audio processing capabilities. It supports microphone input, line-level audio input, and headphone output, enabling a wide range of audio applications from recording to playback.

2. Specifications

The following table outlines the key technical specifications of the ALINX AN831 Audio Capture Module:

3. Package Contents

The standard package for the ALINX AN831 Audio Capture Module includes:

• 1 x ALINX AN831 WM8731 Audio Capture Module

Note: Additional cables, connectors, or development boards are typically sold separately.

4. Setup Guide

4.1 Physical Connections

The AN831 module features three standard 3.5mm audio jacks and a 40-pin header (J3) for connection to a host development board, such as an FPGA board.

• LINE IN (Blue Jack): For line-level audio input from external devices.
• MIC IN (Pink Jack): For microphone input.
• LINE OUT (Green Jack): For headphone or line-level audio output.

4.2 40-Pin Header (J3) Connection

The 40-pin header (J3) provides the digital interface for communication with your development board, including power, ground, and I2C/audio data lines for the WM8731 chip. Ensure correct pin alignment and secure connection to prevent damage.

Refer to Figure 4 for the detailed pin assignment of the J3 connector. Key signals include:

• Power Supply: Pins 2 (5V) and 39, 40 (3.3V).
• Ground: Pins 1, 37, 38.
• I2C Control Interface: VM_I2C_SCLK (Pin 3) and VM_I2C_SDAT (Pin 4) for configuring the WM8731 codec.
• Audio Data Interface: VM_BCLK (Pin 5), VM_DACDAT (Pin 6), VM_DADLRC (Pin 7), VM_ADCDAT (Pin 8), VM_ADCLRC (Pin 9) for digital audio data transfer.

It is crucial to correctly connect these pins to your development board according to your system's requirements and the WM8731 datasheet for proper functionality.

5. Operating Instructions

The ALINX AN831 module acts as an interface between analog audio signals and a digital processing unit (typically an FPGA). Its operation involves configuring the WM8731 codec and managing digital audio data streams.

5.1 WM8731 Codec Configuration

The WM8731 audio codec is configured via an I2C interface. Your host development board (e.g., FPGA) must implement an I2C master to write control registers to the WM8731. This configuration includes setting:

• Sampling rates for ADC and DAC.
• Input gain for microphone and line inputs.
• Output volume for headphones.
• Digital audio interface format (e.g., I2S, Left-justified, Right-justified).
• Power management settings.

Refer to the WM8731 datasheet for a complete list of registers and their functions.

5.2 Audio Capture (A/D Conversion)

1. Connect your audio source (microphone to MIC IN, line-level device to LINE IN).
2. Configure the WM8731's ADC section via I2C, including input selection, gain, and sampling rate.
3. The WM8731 will convert the analog audio to digital data and output it through the audio data interface pins (VM_ADCDAT, VM_ADCLRC, VM_BCLK).
4. Your FPGA or host processor should capture this digital data stream for processing or storage.

5.3 Audio Playback (D/A Conversion)

1. Connect headphones or an amplifier to the LINE OUT jack.
2. Configure the WM8731's DAC section via I2C, including output volume and sampling rate.
3. Your FPGA or host processor should send digital audio data to the module via the audio data interface pins (VM_DACDAT, VM_DADLRC, VM_BCLK).
4. The WM8731 will convert the digital data back to an analog audio signal, which will be available at the LINE OUT jack.

6. User Tips

• Power Sequencing: Ensure that the module receives stable power (5V and 3.3V) before initiating I2C communication or audio data transfer.
• Clock Synchronization: Proper synchronization of the BCLK (Bit Clock) and LRC (Left/Right Clock) signals with your host device is critical for correct audio data transfer.
• Grounding: Maintain a clean ground connection between the AN831 module and your host board to minimize noise in the audio signal.
• Software Drivers: For FPGA integration, you will need to develop custom VHDL/Verilog modules for I2C control and I2S/audio data handling.

7. Troubleshooting

• No Audio Output/Input:
  • Verify all physical connections, especially the 40-pin header and audio jacks.
  • Check power supply voltages (5V and 3.3V).
  • Ensure the WM8731 codec is correctly configured via I2C (e.g., input/output paths enabled, volumes set).
  • Confirm clock signals (BCLK, LRC) are present and correctly synchronized.
• Distorted Audio:
  • Check for proper grounding.
  • Ensure input/output gains are not set too high, causing clipping.
  • Verify sampling rates and data formats are consistent between the codec and the host device.
  • Inspect for loose connections or damaged components.
• I2C Communication Failure:
  • Check I2C clock (SCLK) and data (SDAT) lines for proper connection and signal integrity.
  • Verify the I2C address of the WM8731 (refer to datasheet).
  • Ensure pull-up resistors are correctly implemented on I2C lines if required by your host system.

8. Maintenance

The ALINX AN831 Audio Capture Module is a robust electronic component designed for long-term use. Minimal maintenance is required:

• Cleaning: Keep the module free from dust and debris. Use a soft, dry cloth or compressed air for cleaning. Avoid liquid cleaners.
• Handling: Handle the module by its edges to avoid touching components or pins, which can cause damage from static electricity or physical stress.
• Storage: Store the module in a dry, anti-static environment when not in use.

9. Warranty and Support

For specific warranty information, please refer to the terms and conditions provided by your retailer or the official ALINX website. Technical support and additional resources, including datasheets and example code, may be available through the manufacturer's support channels.

Always consult the official WM8731 datasheet for detailed technical specifications and register configurations.