nRF5340 Audio I2S slave loads bit and frame clock pins when no Bluetooth connection

[GeneF]

I have two nrf5340 audio DKs running bidirectional audio over Bluetooth.  Software is modified Audio example from SDK 2.7.0.  I am trying to run external i2s in the unicast client gateway.  I want to run the i2s port as a slave.  The problem I have is the gateway nrf5340 audio DK is pulling the i2s bit and frame clocks to ground unless there is a Bluetooth audio connection running between the headset and gateway DKs.  If the i2s port is configured as a slave these pins should be inputs.

I can stop the DK from loading the bit and frame clocks after dropping my Bluetooth connection by remarking out the “nrfx_i2s_stop(&i2s_inst);” command in the audio_i2s_stop routine in audio_i2s.c.  However, the clock lines are loaded on power up until I make my first Bluetooth connection.

I am missing something in the i2s slave setup.  Can you help?

[Maria Gilje]

Hello,

I want to run the i2s port as a slave. 

For LE Audio projects the nRF5340 I2S is the master to account for different Bluetooth LE and I2S speeds. This is handled in the drift and presentation compensation modules in the Audio application.

Without the compensation modules, audio artifacts could occur if the speeds are different for Bluetooth LE and I2S. To avoid artifacts you need to compensate for the drift somehow. We have no current solution for this, but we are aware of the use-case.

From internal discussions it appears that you are in contact with a Nordic FAE already, so let me know if you need support here or if you are getting supported directly.

Best regards,

Maria