Bluetooth SCO over PCM ?

[robinsingh]

HI All ,

I am working on bluetooth sco data over PCM at IMX6dl based custom HW  with android 4.4.3 and  I can record audio  by using “tinycap” and played it back on BT headset via “tinyplay” ,  which sound good.

But I get the problem when I tried to play some other  * .wav file(which is not recorded from BT headset.) via tinyplay. all those file sound like faster or someting noise,   So I have a question about sco over pcm.

Does PCM data transferred over PCM bus, need to be SBC encoded if the pcm interface connected with Bluetooth module ?

Thanks

Robin Singh

[vimalbabu]

Hi Robin, Igorpaddykov

I am also using bcm4339 BT chip. I do face a problem in BT SCO over PCM.  My issue is that the PCM signals are not getting generated by bcm4339, i tried to probe at the BCLK and FrameSync pin of bcm4339.

Using hciattach i am able to download the FW to the bcm4339

$ hciattach /dev/ttymxc2 bcm43xx 3000000 flow -t 20

We are able to access bluetooth services.

Using BCM4339 with imx6 sabre auto, i am able to use A2DP and stream music from mobile phone. While trying with HFP i am not getting any PCM signals, i checked the chip's default SCO routing, it is PCM ,following sco routing configuration. So i tried to route SCO packets through UART and HFP is working but quality is low, due to latency.

HCI Log for PCM setting  hcitool cmd 0x3f 0x01D < HCI Command: ogf 0x3f, ocf 0x001d, plen 0 > HCI Event: 0x0e plen 9    01 1D FC 00 00 02 00 01 01 

Following are my concerns please help me to pass through it....

1) What are the necessary steps that i need to do to get PCM signals from BCM4339.....? 

2) What is the mode that BCM4339 is to be configured Master or Slave...?

I request your help to solve this issue...

Regards,

Vimal Babu

[igorpadykov]

Hi robin

reason may be unsupported sample rate by i.MX6 alsa driver, please check

sect.28.2.1, 28.2.2 Stereo CODEC Features attached Linux Manual, also

please try to use aplay described in sect.28.5 Unit Test

Best regards

igor

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[robinsingh]

Hi Igor,

Thanks for the comment , i checked the document you attached . And the sample rate is supported by IMX6 and driver too.

Here is my HW/SW configuration:

1) BT module interfaced on AUDMUX 3 and internal port is SSI, BT module is pcm master and imx6 is slave

2) When i am in sco connection i get a BCLK =256Khz and Framsync = 8Khz from BT moudle to ====>IMX6

3) I modified SSI driver to support "Normal mode to work in plan PCM/TDM "

Now my question is :

Does PCM data transferred over this bus should be SBC encoded or not ?

if it should be SBC encoded then i need to integarte a SBC encoder/decoder ?

I am trying to verify the understanding if somebody can answer here , will be a great help

Thanks

Robin

[igorpadykov]

Hi Robin

I believe it may be useful to check documentation

of this bluetooth module for supported formats.

Best regards

igor