Properly shutting down the I2S stream

[jmcazaux]

Problem Description

Hi Phil,

I am using your libraries in possibly unusual way and faced an issue.
In a nutshell, I am building an audio system with DAB radio (DAB shield piggy back on the ESP 32) and and your AD2P audio library for bluetooth.

I need to feed the audio to an external DAC.
The DAB Shield has an I2S output when Radio is selected.
I can output the I2S to some pin on the ESP32 when the BT source is selected.
I naively tried to connect to my DAC with a "Y soldered" cable like so.

+---------+                          
|  ESP32  +--------+                 
+---------+        |                 
                   |          +-----+
                   +----------+ DAC |
                   |     ^    +-----+
+----------+       |     |           
|DAB Shield+-------+     |           
+----------+             |           
                         |                
               ("Y wire", DATA + BCK + WCK)

The idea is that when the BT source is selected, I shut down the DAB shield and only the ESP32 "talks" to the DAC.
When the radio source is connected, I shut down the I2S on the ESP32 and the DAB shield "talks" to the DAC.
(possibly naive indeed).

It looks like it can work:

• when I power up my system in radio mode, I have the radio playing
• when I power up my system in BT mode, I have the BT source playing.

The issue is when I switch source.
When I switch from BT to radio (shutting down the ESP32 I2S), the radio does not take over (like the ESP32 I2S is not shut down?).

Do you think that the ESP32 I2S could be "not shut down properly"?

If you have a recommendation on how to do this better, please do not hesitate.

Device Description

• ESP32 Wemos D1R32
• DAB shield https://www.dabshield.com/home
• PCM5102 DAC

Sketch

I am not sure you can fully make sense of it, but here is the shut down code:
https://github.com/jmcazaux/esp32_dab_radio/blob/use_dabshield_as_source_of_i2s_clock/firmware/src/main.cpp#L109-L131

Other Steps to Reproduce

No response

What is your development environment (incl. core version info)

CLion + PlatformIO 6.1.19

I have checked existing issues, discussions and online documentation (incl. the Wiki)

• I confirm I have checked existing issues, discussions and online documentation

[pschatzmann]

Calling end() on the I2SStream is shutting down the ESP32 I2S properly!

I guess you also might need to reset the DAC or make the DAC the I2S master...

[jmcazaux]

Mmmhh...
This DAC does not look like it has anything for reset... Or run a master... (this is this one).

Other option I tried was to the DAB shield be the master and let it on at all times (just providing the clock in BT mode), but I think I was not able to set the ESP32 as a slave... It did not work.

[pschatzmann]

Did you try to reset the power to the I2S module manually to check if resolves the issue ?

[jmcazaux]

Hey Phil,

I am a bit lost with what you call the I2S module...

When switching the BT mode off on the ESP32, I call i2s.end(). Is there something else?
And when. switching the radio of, I have a similar API call to switch off the board...

Unfortunately I cannot verify the actual signal (no scope here).

[pschatzmann]

Just disconnect the power pin manually to the DAC module and reconnect it again after switching the source.

If you get audio, this would confirm that the DAC will need to be reset...

[jmcazaux]

Thx, I'll try that

[jmcazaux]

Hey Phil,
I tried the above, but no dice.

When I start in radio mode, the DAC gets the radio signal.
When I switch to Bluetooth, the DAC gets the BT signal.
When I switch back to radio, the DAC remain silent.

Powering on / off the DAC does not bring the sound back.

When I start in BT mode, the DAC gets the BT signal.
When I switch back to radio, the DAC remain silent again.

This is very strange...

The creator of the radio board I use suggested to have the I2S clock being generated by the DAB board at all times and have the ESP32 and the DAC being both slave (clock-whise).

Do you think it could work?

[pschatzmann]

What sample rate and bits are used by your DAB shield ?
When you switch back to radio, the I2S needs to be set up correctly again. So how is your code doing this ?

I think most DAB shields are using 48000 samples per second 16 bits, 2 channels. A2DP is using 44100, 16 bits, 2 channels. Some DAB chipsets require the ESP32 to be the I2S slave instead of master.

[pschatzmann]

Your enableRadio() and disableRadio() is missing the setup and shutdown of I2S!

Alternatively you can just make sure to call I2SStream begin in setup() and change the sample rate via setAudioInfo(), assuming you don't need to change any other I2S settings.

[pschatzmann]

Ignore my last comment: I confirm that when sening data from the DAB the ESP32 I2S must not be active...
So you need to make sure that I2S sent via the DAB shield is working properly. It might be difficult to verify this w/o an Oscilloscope....

Did you test that restaring the radio is working properly ?

• start in radio mode,
• disconnect / reconnect DAC power
• start in radio mode,

Another test you can try to check if the issue is caused by the ESP32:

• disconnect ESP32 BCK and ESP32 LRCK before swithing back to radio mode