DSP Labs
  • INTRODUCTION
  • BILL OF MATERIALS
  • 1. OVERVIEW AND INSTALLATION
    • 1.1 Hardware
    • 1.2 Software
      • CubeMX
      • SW4STM32
      • Eclipse tips
    • 1.3 First project!
  • 2. AUDIO PASSTHROUGH
    • 2.1 Audio I/O theory
      • Microphone
      • Stereo decoder
    • 2.2 Updating peripherals
    • 2.3 Wiring audio I/O
    • 2.4 Coding passthrough
  • 3. ALIEN VOICE EFFECT
    • 3.1 How it works
    • 3.2 Real-time DSP tips
    • 3.3 Real-time with Python
    • 3.4 C implementation
  • 4. DIGITAL FILTER DESIGN
    • 4.1 Design approaches
    • 4.2 Real-time implementation
  • 5. GRANULAR SYNTHESIS
    • 5.1 How it works
    • 5.2 Implementation
  • 6. LINEAR PREDICTION
    • 6.1 Theory behind LPC
    • 6.2 Implementation
  • 7. DFT PITCH SHIFTING
    • 7.1 How it works
    • 7.2 Python implementation
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  1. 2. AUDIO PASSTHROUGH

2.1 Audio I/O theory

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Last updated 6 years ago

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The microphone and DAC components we will be using rely on the I2S (Inter-IC Sound) bus specification for audio transfer. This is a 3-line serial bus consisting of:

  1. A data line for two time-multiplexed channels (usually denoted as left and right).

  2. A word select line for indicating which of the two channels is being transmitted/received.

  3. A clock line for which each period will correspond to a unique bit of data.

More information about the I2S bus specification can be read .

We first discuss the I2S protocol with respect to the and then for the . We recommend reading in this order as the microphone section is easier to grasp and will introduce common terminology used later on.

For the STM board that we are using, we will configure two I2S buses: one for input and the other for output. This configuration process will be covered in .

here
microphone
DAC
Chapter 2.2