Create audio.md

Author: marcel-licence

extras/audio.md

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+# Audio Codec Interface with Microcontroller
+
+This project demonstrates how to set up and interface an audio codec with a microcontroller using I2S communication. It covers the necessary signal connections, configuration options, and a test signal mode for validation.
+
+## Getting Started
+
+### Overview of Audio Codec Signals
+
+When interfacing an audio codec with a microcontroller, several key signals are involved:
+
+- **BCLK (Bit Clock)**: This is the clock signal that synchronizes the data transfer between the microcontroller and the codec. It defines the speed at which bits are transferred.
+- **WCLK (Word Clock) / LRCLK (Left-Right Clock)**: This signal specifies the sample rate and is used to separate left and right audio channels.
+- **DIN (Data In)**: The data input pin on the codec, where audio data is received from the microcontroller.
+- **DOUT (Data Out)**: The data output pin on the microcontroller, where audio data is sent to the codec.
+
+The microcontroller must be configured to use I2S for these signals, ensuring the codec receives the audio data correctly.
+
+### Configuration
+
+The configuration options for this project are specified in `config.h`. Important parameters include:
+
+- **`SAMPLE_RATE`**: Defines the audio sampling rate.
+- **`SAMPLE_BUFFER_SIZE`**: Determines the buffer size for audio data. This impacts the generated test frequency if enabled.
+
+To test your setup, you can enable a saw wave test signal by defining `OUTPUT_SAW_TEST` in `config.h`. This test signal will output a saw wave with a frequency calculated as:
+
+```c
+Frequency = SAMPLE_RATE / SAMPLE_BUFFER_SIZE
+```
+
+Example:
+```c
+#define OUTPUT_SAW_TEST  // Uncomment to enable the saw wave test signal
+```
+
+### Codec-Specific Considerations
+
+Some codecs may require additional configuration:
+
+- **I2S Configuration**: Most audio codecs can be configured over I2S. Ensure that your microcontroller's I2S settings (bit depth, sample rate, etc.) are compatible with the codec's specifications.
+- **Additional Pins**: Certain codecs, such as the PCM5201a, may have additional pins like a *Mute* pin. Refer to the codec-specific documentation [PCM5102a](ml_pcm5102a) for details on these configurations.
+
+### Running the Project
+
+1. **Flash the Firmware**: Program the microcontroller with the provided firmware.
+2. **Check Serial Monitor**: After starting the firmware, open the serial monitor. The monitor will display the pin settings for the I2S interface, allowing you to verify correct signal connections and configuration.
+
+## Contributing and Support
+
+For questions, feedback, or further assistance, feel free to start a discussion on the GitHub repository.
+
+Happy coding!