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OVMS3-idf/examples/peripherals/i2s_adc_dac/README.md
Wangjialin 2fceec4d85 feature(I2S-ADC): add ADC mode for I2S. 
1. Support built-in ADC for I2S.
2. Modify code of ADC, made no change to the original APIs.
3. Add APIs in I2S:
esp_err_t i2s_set_adc_mode(adc_unit_t adc_unit, adc1_channel_t adc_channel);
4. Add I2S ADC/DAC example code.
5. add old-fashion definition to make it more compatible
6. replase spi_flash_ APIs with esp_partition_ APIs
7. add example of generating audio table from wav
8. change example sound
2017-09-14 13:24:08 +08:00

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I2S built-in ADC/DAC Example

  • This is an example of:
    • Recording sound from ADC
    • Replay the recorded sound via DAC
    • Play an audio file in flash
  • Run this example
    • Set partition table to "partitions_adc_dac_example.csv" in menuconfig, or rename sdkconfig.default to sdkconfig directly.
    • Set IDF_PATH and run "make flash"
  • This example will execute the following steps:
    1. Erase flash
    2. Record audio from ADC and save in flash
    3. Read flash and replay the sound via DAC
    4. Play an example audio file(file format: 8bit/8khz/single channel)
    5. Loop back to step 3
  • Hardware connection:
    ESP32 Microphone + amplifier amplifier + speaker
    GPIO36(ADC1CH0 input) data output pin
    GPIO25(DAC1 output) right channel speaker input
    GPIO26(DAC2 output) left channel speaker input

  • How to generate audio files:

    • tools/generate_audio_file.py is an example of generate audio table from .wav files.
    • In this example, the wav file must be in 16k/16bit mono format.
    • generate_audio_file.py will bundle the wav files into a single table named audio_example_file.h
    • Since the ADC can only play 8-bit data, the script will scale each 16-bit value to a 8-bit value.
    • Since the ADC can only output positive value, the script will turn a signed value into an unsigned value.
  • Note:
    • DAC can only play 8-bit data, so the wav file data are scaled to 8-bit data.
    • I2S DMA can only output 16-bit/32-bit data to DAC, DAC will only take the highest 8-bit data and output accordingly.
    • Before I2S DMA can output data stream to DAC, the data format should be converted to 16-bit or 32-bit by padding zeros.