BC127 analog audio volume unstable

IoT Modules
1

Hello,

since a longer time I try to find the reason for my audio problem without success, so maybe someone can help…

I have an own pcb with the BC127. The BC127 audio in (left channel) is connected to the speaker out of a voice recorder. The BC127 has BT connection (AGHFP) to a headphone with HFP1.5.

No I am trying to optimise the audio connection impedance/signal but I am running in the following problem:

I start the voice recorder only for short time and the volume in the headset grows up and a loud noise can be heared. This does not happen on every time. Sometimes noise becomes louder, sometimes it becomes less loud. If it is loud I can reset it by sending the ‘VOLUME 12 8’ Command. The noise is away immediately. Playing around again until noise is loude and reading the ‘VOLUME 12’ says it is ‘8’, but sending ‘VOLUME 12 8’ again resets the noise again.

It is not clear to me what happens here. It feels like the volume changes alone, but the requested volume level does not show me different setting.

I already tried HFP_CONFIG=OFF OFF OFF OFF ON OFF setting to disable wide range (HFP1.6) and noise cancelling …

Does anybody have an idea what may be the reason for the noise issue and why it is impressionabel by the VOLUME command?

Best Regards
Christian

2

I played around with another board (sparkfun Jamboree) Firmware 6.1.5.
I connected the computer audio out to the Line in of the Jamboree - paiered the BC127 with the audio headset - connected a terminal to the Jamboree and opened a AGHFP session.
Audio can be eared in the headset. Now I stop the music player on the computer just to heare the buzzing of some regutator or so (does not care). Now I send ‘VOLUME 12 8’ again and again to the BC127 and can hear the volume change (I can hear that something happens in the BC127 when it receives the volume command).

So still my question is - what happens inside the module when it receives the ‘VOLUME’ command?

I Hope there is somebody of you that can help me, … maybe after the weekend :slight_smile:
Many thanks,