using the I2S output as slave (connect to a ADAU1701 DSP)

[jmibk]

I try to use the arduino audio tools lib in connection with an ESP32 board to stream Bluetooth to I2S and then into an Audio DSP I2S input.

If I connect any DAC to the I2C output of the ESP, everything works great.

Now if I connect the ESP32 to the DSP, the DSP is the master device, so it delivers a clock itself. In that case I have to feed the ESP32 with the clock signals from the DSP. I think this must be called I2S output as slave on the ESP32.

I don't know, how to configure the I2S on the ESP to this slave mode, that the DSP gives the bit (or master) clock to the ESP?

Has anyone connected a ESP32 with the arduino audio tools lib to any external DSP that operates in master mode?

This is my setup code based on the Basic A2DP to I2S example.

`void setup() {
Serial.begin(115200);
AudioLogger::instance().begin(Serial, AudioLogger::Warning);

// register callback
a2dp_sink.set_stream_reader(read_data_stream, false);

// Start Bluetooth Audio Receiver
a2dp_sink.set_auto_reconnect(false);
a2dp_sink.start("a2dp-i2s");

// setup output
auto cfg = i2s.defaultConfig();
cfg.pin_data = 13;
cfg.pin_ws = 14;
cfg.pin_bck = 15;
cfg.sample_rate = a2dp_sink.sample_rate();
cfg.channels = 2;
cfg.bits_per_sample = 16;
//cfg.is_master = false; //is not working.
i2s.begin(cfg);
}`

[pschatzmann]

if cfg.is_master = false; then the ESP32 expects that the values for pin_bck and pin_ws are provided by the external system.
If this is not working I would suggest to look for the issue on the Audio DSP side.

I have never tried but I doubt that this is also working for the pin_mck.

In any case I would recommend to start your tests with a sine generator sketch and not with something as complicated as A2DP...

[jmibk]

Thanks for the really quick answer.

I fed the ESP32 with the LRClock (48kHz, Pin14) and the BitClock (around 3,07MHz, Pin15) from the DSP.
Signals look OK on the scope.

There is no serial audio data on the data pin of the I2S on the ESP32 (Pin 13).

Bluetooth from my phone is connected and streaming audio.
Edit: the line "cfg.is_master = false;" is active and uploaded.

[pschatzmann]

You can try to log the result length of the data which is written to i2s, just to make sure that the write is really working.

To be honest I never tried this scenario - only one where an external DAC was the master and providing the data to the ESP32, but I would be really surprised if the ESP32 would not support this...

ps. Do you get the same frequencies if you use the ESP32 as Master?

[jmibk]

Everything seems right - only not the output of signals ;)

There is this configuration thing, that initializes with:

I2SStream i2s;

and later does the setup:

auto cfg = i2s.defaultConfig();
...
i2s.begin(cfg);

There you can set most of the I2S pins like

cfg.pin_data = 13;
cfg.pin_ws = 14;
cfg.pin_bck = 15;

In the Espressif docs there is also a master clock pin.
Does this also exist in the cfg. config - someting like this?

cfg.pin_mclk = 3; //or cfg.pin_mck = 3;

I tried also something like

i2s.i2s_set_pin(3, mck_io_num); //this is out of espressifs doku

but with no success.

[pschatzmann]

That would be the pin_mck from my second last answer - and as I have mentioned I would be surprised if that would be supported as input. Let me know about your findings