HELP: 2kHz square-wave superimposed on speaker output signal making wailing sound while using hands-free profile (HFP)


#1

Hello,
We’re having a frustrating problem with the bluetooth module BC-127-HD.
It’s been integrated in one of our products and everything is working fine except for the most important feature, the HFP.
When we are streaming media sound through A2DP, everything sound good but when we switch to HFP and connect a call we get a wailing sound. Measuring it with a oscilloscope it looks like a square-wave with 2kHz frequency.
Also, the quality of the speech is awful, almost unrecognizable.

We are desperate for some help. Have anyone else experienced the same problem?
The module is connected to a sinlge-ended amplifier chip and a 11x15mm speaker, same as in Sony Xperia Z3/Z4.
A high pass filter has been implemented and is configured around 100Hz and the recommended capacitors, as described in the BC127 datasheet, have also been added.

We’ve tried to remove the microphone but the sound remains the same.
Our product is battery driven.

We are starting to feel really desperate as this is our final obstacle stopping us from releasing the product for production.

Please help!

Best regards
Derry Malmberg

Our BT-module configuration looks like this:

BlueCreation Copyright 2017
Melody Audio V6.1.5 HD
Build: 1496941831
Ready
ERROR 0x0012
AUDIO=0 0
AUDIO_ANALOG=15 15 1 OFF
AUDIO_DIGITAL=0 44100 64 100A00 OFF
AUTOCONN=0
AUTO_DATA=OFF OFF OFF
BALANCE=100 100
BATT_CONFIG=ON 150 4150 5000 200
BC_SMART_CONFIG=68E3 28F0 89F7 D93C
BEACON_DATA=0 00 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF 04 D2 16 2E EE
BLE_CONFIG=0 OFF 40 ON
BLE_CONN_PARAMS=128 12 6 40 0 400 50 400 400 61 400 400
BT_VOL_CONFIG=A A 10 1
CLASS_1=OFF
CMD_TO=20
COD=240404
CODEC=8 OFF
CONN_TO=0
DEEP_SLEEP=OFF
DEVICE_ID=0001 0002 0003 0004 0005 0006 0007 0008
DISCOVERABLE=0 0
ENABLE_BATT_IND=ON
ENABLE_CAPSENSE=OFF
ENABLE_LED=ON
ENABLE_SPP_SNIFF=OFF 0 0 0 0 0
GPIO_CONFIG=ON 0 255
HFP_CONFIG=OFF ON OFF OFF OFF
HIGH_SPEED=OFF OFF
LOCAL_ADDR=20FABB09BF33
MAX_REC=2
MM=OFF OFF 0 OFF OFF OFF OFF OFF
MUSIC_META_DATA=OFF
MUSIC_OLD_AVRCP=OFF
NAME=V. BT-Version
NAME_SHORT=BC9BF33
PIN=0000
PROFILES=1 0 0 1 1 0 0 0 0 0 0 0
REMOTE_ADDR=000000000000
SPP_UUID=00 00 11 01 00 00 10 00 80 00 00 80 5F 9B 34 FB
SSP_CAPS=3
TWS_CONFIG=OFF 1 2
UART_CONFIG=9600 OFF 0
USB_HOST=OFF
VREG_ROLE=1
OK