(r4) I2SAndSound < IoT_Course

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---+ !I2S and sound
---++ Introduction

In order to play audio files we need:
   * the audio file itself, which we expect to be in uncompressed wav format
   * a file system from which to read the file. This is available in !MicroPython either in its internal flash or on an SD card
   * a fast 16 bit DAC to convert the audio data into an analogue form that can be consumed by a loadspeaker
   * an amplifier to get enough signal power needed for the loadspeaker
   * a software driver implementing the !I2S protocol
The digital data must be transferred to the DAC, which is done through the [[https://diyi0t.com/i2s-sound-tutorial-for-esp32/][I2S protocol ]]invented by Philips in the end 1980 ies.

There are two cheap !I2S boards converting digital audio data to an analogue audio signal and communicating through the !I2S protocol:
   * the ! [[https://datasheets.maximintegrated.com/en/ds/MAX98357A-MAX98357B.pdf][MAX98357A]], a mono converter board with integrated amplifier to which we can directly connect a loadspeaker
   * the [[https://www.ti.com/lit/ds/symlink/pcm5102a.pdf?ts=1611472691830&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FPCM5102A][PCM5102a]], a stereo converter board with a connector for head phones. If we want to connect a loudspeaker to this board we have to pass through an audio amplifier.
---++ Connecting the !MAX98357A

<img alt="max98357a.png" src="%ATTACHURL%/max98357a.png" title="max98357a.png" />

Here is a table showing how I connected the !MAX98357A to the ESP32 board:

| !MAX98357A pin | pin on ESP32 CPU card | signification |
| Gnd | Gnd | |
| Vcc | 3.3V | |
| SD | n.c. | |
| Gain | Gnd | important: don't leave this pin floating! |
| Din | D2: GPIO 21 | audio data |
| BCLK | D0: GPIO 26 | bit clock |
| LRC (LRCLK) | D1: GPIO 22 | left/right clock |
---++ Connecting the PCM5102:
| <img alt="pcm5102.png" height="285" src="%ATTACHURL%/pcm5102.png" title="pcm5102.png" width="420" /> | <img alt="pcm5102back.png" src="%ATTACHURL%/pcm5102back.png" title="pcm5102back.png" /> |

| PCM5102 pin | pin on ESP32 CPU card | signification |
| Vcc | 5V | |
| Gnd | Gnd | |
| BCK | D0: GPIO 26 | bit clock |
| Din | D2: GPIO 21 | audio data |
| LRCLK | D1: GPIO 22 | left/right clock |
| FMT | Gnd | |
| XSMT short-circuit with !A3V3 | | 3.3 V output from regulator LDO |
The SD card module, which may be used to store the music files, uses D5,D6,D7,D8 for its interface pins. These pins should therefore be avoided when choosing the pins for the PCM5102 module. D3 and D4 are used for PSRAM in case of the WROVER-B module.
---++ !I2S examples

Mike Teachman, the author of the !I2S !MicroPython driver has supplied a series [[https://github.com/miketeachman/micropython-i2s-examples][of test programs]] for his driver. These examples need some slight modifications due to different connections of the !I2S pins with respect to his hardware:
   * SCK_PIN: corresponds to the hardware pin BCK and must be set to GPIO 26
   * WS_PIN: corresponds to hardware pin LRCK and must be set to GPIO 22
   * SD_PIN: corresponds to hardware pin Din and must be set to GPIO 21
With these modifications, _play-tone.py_ should work. In order to make play-wav-from-flash-blocking.py work modified the WAV_FILE to wav/side-to-side-8k-16bits-stereo.wav. Then I created the folder /wav on the ESP32 with ampy and copied _side-to-side-8k-16bits-stereo.wav_ to the folder.

-- %USERSIG{UliRaich - 2021-01-24}%

---++ Comments

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Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	max98357a.png	r1	manage	203.5 K	2021-01-24 - 16:23	UliRaich
png	pcm5102.png	r1	manage	127.0 K	2021-01-24 - 16:23	UliRaich
png	pcm5102back.png	r1	manage	88.2 K	2021-01-24 - 17:48	UliRaich
Topic revision: r4 - 2021-07-07 - UliRaich