Audio Interface

Created: 5/12/2020Lasted updated:5/12/2020

Introduction

Audio signal transmission are standardized on protocol and interface levels. Common audio analog and digital interfaces are explained.

Background

Inter-IC (i.e audio signal transferring within an audio equipment)

      • Digital Audio Communication Standard/Protocol
        • Stereo-Channel Audio
          • PDM
            • Up to 2 Digital Microphones
            • BUS Type
              • 2 wire interface
              • Pins
                • Data
                • Clock
          • I2S
            • Up to 2 channels
            • Bus Type
              • 3/4 wires interface
              • Configuration
                • Master/Slave Configuration
                • Half/Full Duplex Communication
              • Pins
                • BLCLK - Bit Clock
                • LRCLK - Word Clock
                • SDOUT -Data Out
                • SDIN -Data in
                • MCLK- Master Clock
                • Note: Typically BLCK, LRCLK and SDOUT/SDIN (Master/Slave) are used.
        • Multi-Channel Audio
          • TDM
            • Up to 16 channels
            • Bus Type
              • Master/Slave Configuration)
              • Half/Full Duplex Communication
              • Pins
                • SCLK
                • FSYNC
                • SDATA -Din
                • SDATA -Dout
          • Advanced audio interface
          • Slimbus
            • Combines audio stream and control signals in one
            • Found in Mobile device
            • TDM type
            • Wiring
              • CLK
              • Data
          • Soundwire
            • Combines audio stream and control signals
            • Found in Mobile device
            • TDM type
            • Supports PCM and PDM
              • Wiring
                • CLK
                • Data
        • Analog
            • Line out/line in


Inter-board (i.e audio signal transferring between equipment)

        • Digital Audio
          • Communication Standard/Protocol
            • SPDIF
              • Audio Format
                • Uncompressed
                  • 2CH PCM
                • Compressed
                  • 5.1/7.1 Surround Sound (DD, DTS)
              • Physical Interface (cable and connector)
                • Optical
                  • Data transmission through Fiber optic cable with Toslink connector
                • Electrical
                  • Data transmission through Coaxial Cable with RCA connector
                  • Data transmission through ARC with HDMI connector
            • ADAT
              • Audio Format
                • Uncompressed
                  • 24Bits/48kHz/8CH PCM
                  • 24Bits/96kHz/4CH PCM
                • Compressed
                  • TBD
              • Physical Interface (cable and connector)
                • Optical
                  • Data transmission through Fiber optic cable with Toslink connector
            • USB Audio
              • Physical interface
                • USB transmission line and USB connectors.
        • Analog Interface
          • Unbalanced voltage waveform (i.e Line-in/out)
              • Physical Interface (cable and connector)
                • 3.5mm audio jack
            • Balanced voltage waveform
              • Physical Interface (cable and connector)
                • XLR connector
        • Wireless Interface
          • Bluetooth Classic (EDR, BDR)
            • Profile A2DP
            • Audio Format
              • Compressed
                • SBC, AAC, LDAC
          • Bluetooth Low Energy (BLE)
            • Profile Gatt
            • Audio Format
              • Compressed
                • ADPCM
                • OPUS

Design analysis

Most common inter IC digital audio audio are I2S and TDM interfaces.

Most common inter board digital audio interface are SPDIF with physical transmission medium in optical (TOSHLINK connector) format.

Q&A

Summary & Conclusion

  • Inter IC connection is the interface within the electronic equipment
  • Inter board connection is the interface among different electronic equipment.
  • Audio transmission can be optical or analog.
  • Audio format can be RAW (PCM) or compressed audio (AC3)

Further Reading