I2S input - what boards support it

[erlendf]

I want to connect an I2S audio source to the microcontroller. With Feather S2 ESP32 I have got I2S output working, but the Feather does not seem to have support for either hardware I2S input, nor a driver. To test I have the Mems I2S microphone break-out. I prefer using Circuitpython. If required, I would like to buy a more suited microcontroller, but it should also have wi-fi and Circuitpython. I just do not know which board to buy - or if I have to?

[mikeysklar]

@erlendf,

Have you tried running the "Where's my PDMIn?" code example on your Feather S2?

https://learn.adafruit.com/adafruit-pdm ... 3038798-11

Code: Select all

import board
import audiobusio
from microcontroller import Pin


def is_hardware_PDM(clock, data):
    try:
        p = audiobusio.PDMIn(clock, data)
        p.deinit()
        return True
    except ValueError:
        return False
    except RuntimeError:
        return True


def get_unique_pins():
    exclude = ['NEOPIXEL', 'APA102_MOSI', 'APA102_SCK']
    pins = [pin for pin in [
        getattr(board, p) for p in dir(board) if p not in exclude]
            if isinstance(pin, Pin)]
    unique = []
    for p in pins:
        if p not in unique:
            unique.append(p)
    return unique


for clock_pin in get_unique_pins():
    for data_pin in get_unique_pins():
        if clock_pin is data_pin:
            continue
        if is_hardware_PDM(clock_pin, data_pin):
            print("Clock pin:", clock_pin, "\t Data pin:", data_pin)
        else:
            pass

[erlendf]

PDM or I2S - Adafruit says two opposite things:
About the PDM microphone board you say: It's digital but its not PWM and it's not I2S. Then in an other place you say: It's easy to use the Adafruit PDM microphone breakout with CircuitPython, using the built-in audiobusio module and PDMIn class. It allows you to record an input audio signal from the microphone using I2S. Then, about the I2S microphone board you say: , you will often find an I2S peripheral, that can take digital audio data in! That's where this I2S Microphone Breakout comes in.
I am confused; I thought PDM was a raw pulse coded format, whereas I2S is a digital protocol - and that the two have nothing to do with each other. With the I2S microphone breakout do I not simply need the microcontroller to read the I2S protocol as an input? Does anybody know of a microcontroller that does this?

[erlendf]

@mikeysklar, thank you for your reply, but as I am describing in my latest post it is not PDM I want, but I2S.

[mikeysklar]

@erlendf,

At this time with CircuitPython the only support I see is for I2SOut and PDMIn. This is why I suggested running the PDMIn code. In our docs we still consider PDMIn to be recording over I2S.

https://circuitpython.readthedocs.io/en ... hlight=i2s

There is some example code to discover usable I2S output pins, but nothing for I2S input.

https://learn.adafruit.com/adafruit-max ... iring-test

Code: Select all

import board
import audiobusio
from microcontroller import Pin


def is_hardware_i2s(bit_clock, word_select, data):
    try:
        p = audiobusio.I2SOut(bit_clock, word_select, data)
        p.deinit()
        return True
    except ValueError:
        return False


def get_unique_pins():
    exclude = ['NEOPIXEL', 'APA102_MOSI', 'APA102_SCK']
    pins = [pin for pin in [
        getattr(board, p) for p in dir(board) if p not in exclude]
            if isinstance(pin, Pin)]
    unique = []
    for p in pins:
        if p not in unique:
            unique.append(p)
    return unique


for bit_clock_pin in get_unique_pins():
    for word_select_pin in get_unique_pins():
        for data_pin in get_unique_pins():
            if bit_clock_pin is word_select_pin or bit_clock_pin is data_pin or word_select_pin\
                    is data_pin:
                continue
            if is_hardware_i2s(bit_clock_pin, word_select_pin, data_pin):
                print("Bit clock pin:", bit_clock_pin, "\t Word select pin:", word_select_pin,
                      "\t Data pin:", data_pin)
            else:
                pass

[erlendf]

Thanks, but it makes me wonder what the Adafruit I2S MEMS Mic breakout is for? It specifically says that it is not PDM, but I2S.

Regards,
Erlend

[mikeysklar]

Erlend,

On the Arduino side I2S mic input is supported as I2S not PDMin.

https://learn.adafruit.com/adafruit-i2s ... g-and-test

https://github.com/adafruit/Adafruit_ZeroI2S

https://www.arduino.cc/en/Tutorial/Libr ... ialPlotter

[erlendf]

@mikeysklar, thank you for your reply. I will put the I2S ambition to rest for now, then - until someday there will be CircuitPython support for it. Instead I will connect my Feather M4 to a separate audio recorder/player with it's own Flash, codec, and uC. The benefit is also that the audio work will not bog down the M4. I intend to test out a board callled SOMO II for this purpose, because the codec from Ada would unfortunately need the M4 to do the processing.

My application needs to play audio from a range of short soundbites, as well as be able to record 1 soundbite of max 15sec, that can be replayed later.

Thanks for clarifying the I2S stuff,
Erlend