BT1026C - Analog microphone stops working when I2S is enabled

mehmet

Dear Feasycom Team,
I have been testing the FSC-BT1026C (+VER=FSC-BT1026C,V4.9.4,20230428) and have read the datasheet and AT command documentation, but I could not find any information regarding this behavior.

My hardware setup is:

Analog electret microphone connected to the MIC input.
HFP profile for hands-free calls.
I2S intended to be used only for audio output (to an external amplifier). No I2S microphone or external audio codec is connected.
Test results

Case 1: AT+I2SCFG=0

HFP call works normally.
The analog microphone works correctly.
MIC_BIAS voltage is present.

Case 2: AT+I2SCFG=5 (I2S enabled)

The analog microphone no longer works during HFP calls.
MIC_BIAS voltage is no longer generated.
The only change between the two tests is the AT+I2SCFG setting.

Could you please clarify:

Is this the expected behavior of the BT1026C firmware?
Does enabling I2S automatically disable the analog microphone path and MIC_BIAS?
Is there any additional AT command or configuration required to keep the analog microphone enabled while using I2S only for audio output?

Thank you for your support.
Best regards.

FAE_Gavin

mehmet Yes, this is the expected behavior.

When I2S is enabled (AT+I2SCFG=5), the analog audio input path will be disabled, including MIC_BIAS output. The FSC-BT1026C does not support using the analog microphone input and I2S interface simultaneously.

mehmet

Thank you for the clarification, Gavin. We appreciate your support.