I2SStream and AnalogStream on the same I2S port?

[grygol]

Hello,
I'm trying to find out if it's possible for this wonderful library to use the same I2S port when dealing with the I2S input and the analog output. I have a case where I have only one I2S interface free to use and am trying to find out if it's even possible to combine these two stream approaches.

What is my case?

On ESP32 I need to catch audio from my I2S mic (INMP441) and then stream it using e.x. AudioWavServer. Meanwhile at the same time I need to catch audio from URLStream and output it to analog amplifier (LM386). The most important (and I think challenging) thing here is that I can use only one I2S port.

What is the issue?

When using two Streams separately with two different I2S ports, everything works fine, but when using one I2SStream in RXTX_MODE, I get huge noise on output with barely hearable correct audio.

My findings

While doing my research I found information that I2S is duplex so if I understand correctly it should separate input and output audio and provide correct one for each. I also noticed that RXTX mode is not supported in AnalogStream. I tried to combine these two classes - taking I2SStream pieces for config and reading, and AnalogStream write for output, but it didn't work as expected.

My question

So here I started to wonder if it's even possible to combine these two streams? So have I2S on input and analog on output. Or should I rather replace analog amplifier with some I2S output module, but will it work as I need it to then? I feel I'm missing something here...

Maybe someone had similar case or issue and could provide some clues what can be done here? I would appreciate any help or advice.

My code

Here's my code pieces which I tried while looking for a right way...
I tried also some different configurations and approaches but I don't think they are any significant to understand my problem. I also removed non-important lines from this issue perspective.

Mic only - working

AudioWAVServer server(ssid, password, 4713);
I2SStream i2sStream;
ConverterFillLeftAndRight<int16_t> filler(RightIsEmpty);

void init_audio_in() {
    auto config = i2sStream.defaultConfig(RX_MODE);
    config.is_master = true;
    config.i2s_format = I2S_STD_FORMAT;
    config.sample_rate = 44100;
    config.channels = 2;
    config.bits_per_sample = 16;
    config.pin_ws = 15;
    config.pin_bck = 14;
    config.port_no = 1;
    config.pin_data = 32;
    i2sStream.begin(config);
    server.begin(i2sStream, config, &filler);
}

Audio output only - working

URLStream url(ssid, password);
AnalogAudioStream out; // final output of decoded stream
EncodedAudioStream dec(&out, new MP3DecoderHelix()); // Decoding stream
StreamCopy copier(dec, url); // copy url to decoder

void setup(){
  auto config = out.defaultConfig(TX_MODE);
  out.begin(config);

  dec.setNotifyAudioChange(out);
  dec.begin();

  url.begin("http://stream.srg-ssr.ch/m/rsj/mp3_128","audio/mp3");
}

void loop(){
  copier.copy();
}

Input to Output - I used i2s-i2s example here. Not working (huge noise on output with barely hearable correct audio)

AudioInfo info(44100, 2, 16);
I2SStream i2s;
StreamCopy copier(i2s, i2s); // copies sound into i2s
ConverterFillLeftAndRight<int16_t> filler(RightIsEmpty);

void setup(void) {  
  auto config = i2s.defaultConfig(RXTX_MODE);
  config.copyFrom(info); 
  config.is_master = true;
  config.i2s_format = I2S_STD_FORMAT;
  config.sample_rate = 44100;
  config.channels = 2;
  config.bits_per_sample = 16;
  config.pin_ws = 15;
  config.pin_bck = 14;
  config.port_no = 1;
  config.pin_data = 25;
  config.pin_data_rx = 32;
  i2s.begin(config);
}

void loop() {
  copier.copy(filler);
}

My custom class which I tried to use to have analog output. Didn't work as I suppose there could be some issue with DAC configuration

class I2SInputAnalogOutputStream : public I2SStream
    {
    public:
        I2SInputAnalogOutputStream() = default;

        size_t write(const uint8_t *src, size_t size_bytes) override
        {
            size_t result = 0;
            I2SConfig cfg = i2s.config();
            i2s_port_t port_no;

            switch (cfg.port_no)
            {
            case 0:
                port_no = I2S_NUM_0;
                break;
            case 1:
                port_no = I2S_NUM_1;
                break;
            default:
                port_no = I2S_NUM_MAX;
                break;
            }

            if (size_bytes > 0 && src != nullptr)
            {
                TRACED();
                size_t output_size = 0;
                size_t result;
                uint16_t *dst = (uint16_t *)src;

                // Only case for 24 bit left
                int24_t *data = (int24_t *)src;
                output_size = (size_bytes / 3) * 2;
                for (int j = 0; j < size_bytes / 3; j++)
                {
                    dst[j] = (uint32_t)convert8DAC(data[j], 24);
                }

                if (output_size > 0)
                {
                    if (i2s_write(port_no, src, output_size, &result, portMAX_DELAY) != ESP_OK)
                    {
                        LOGE("%s: %d", LOG_METHOD, output_size);
                    }
                }

                LOGD("i2s_write %d -> %d bytes", size_bytes, result);
                return result;
            }

            return size_bytes;
        }
    };

[pschatzmann]

There are 2 ports (0 and 1) and you can use only one port at a time (to do i2s or analog input or output via the i2s api)!
In addition all analog operations (input or output) need to be on port 0.

So this means:

• you can't use analog input and output at the same time (because both require port 0)
• if you have analog input (or output) (which must be using port 0) and a regular i2s (simplex or douplex), i2s has to to be on port 1!

For the INMP441 I have the gut feeling that you just ignored my information in the documentation

[grygol]

Thank you very much!