1.1 Hardware
In this section, we introduce the different hardware components that will be used in our lab exercises:
Both the microphone and the DAC will rely on the I2S (Inter-IC Sound) bus specification for audio transfer. This is a 3-line serial bus consisting of a data line for two time-multiplexed channels, a word select line, and a clock line. More information about the I2S bus specification can be found here.
Microcontroller
The board we will be using comes from the STM32 Nucleo-64 family. In particular, we will be using the STM32 Nucleo-64 development board with the STM32F072RB microcontroller unit. You can find more information about this family of boards by reading the official documentation.
Figure: STM32 Nucleo development board. Picture source.
Microphone
The microphone part we will be using is the I2S MEMS Microphone Breakout by Adafruit. We describe the component in more detail in the following chapter, as we build a passthrough (passing the microphone input directly to the output), which is the "hello world" equivalent for audio.
Figure: Adafruit I2S MEMS Microphone Breakout. Picture source.
DAC + Audio Jack
The microphone we are using measures an analog (continuous in time and amplitude) signal and returns a digital (discrete in time and amplitude) signal, which can be further processed by our microcontroller. In order to playback or listen to this digital signal, it is necessary to convert it back to an analog signal; this can be done with a DAC (Digital-to-Analog Converter). We will be using Adafruit's I2S Stereo Decoder Breakout, which contains the DAC, an audio jack for connecting headphones, and the necessary additional components. We will describe the DAC in more detail as we build a passthrough in the following chapter.
Figure: Adafruit I2S Stereo Decoder - UDA1334A Breakout. Picture source.
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