XMOS as I2S Slave on U16 Mch

[vicacid]

Hi there,

I am quiet new to XMOS products and have a question regarding the I2S clock generation on the U16 Multichannel Platform (XP-SKC-U16 with XA-SK-AUDIO8).

I'd like to set the XMOS to I2S slave mode and use the CS5368 as the clock master. To achieve this, I modified the project "app_usb_aud_skx_u16_audio8" in xTIMEcomposer. Specifically, I changed CODEC_MASTER to (1) in "devicedefines.h" (belonging to "module_us_audio") and rebuilt all. 

Running the application on the hardware changes nothing regarding the clock behaviour. The reason seems to be that the change of CODEC_MASTER is not recognized in the main project.

Do I have to change some additional settings, or is it the wrong parameter that I modified?

Thanks in advance.

[Vineela]

Setting CODEC_MASTER as '1' should set the CODEC as I2S master. Recomended way to do this is to set this define in customdefines.h file of app_usb_aud_skc_u16_audio8. 

"Running the application on the hardware changes nothing regarding the clock behaviour. The reason seems to be that the change of CODEC_MASTER is not recognized in the main project."

Expected behaviour is instead of XMOS device CODEC should be driving the BCLK and LRCLK. How are you ensuring this clock behaviour?

[vicacid]

Hi Vineela,

thanks for your reply. I tried setting the XMOS as clock slave by setting the define in "customdefines.h", but the XMOS still remains clokc master. 

I verify this by looking at the I2C data sent to the CS5368 and this data is always 0x97, regardless of the value of CODEC_MASTER. So the Codec is always configured to be slave and since the clock starts running when the program runs, the XMOS still must be the clockmaster.

I suppose there must be some additional changes be done to the code to set the XMOS as clock-slave. Any idea?

 

Thanks,

Stephan

 

[krishnabalan]

Hi Stephan,

I just looked at the "app_usb_aud_skc_u16_audio8" and found that the CODEC_MASTER is properly taken care in setting up the CS5368 device in audiohw.xc.

There is also a build configuration called "2io_slave" present in the project (Makefile) which complies the code for XMOS to act as slave (i.e CODEC as master).  Can you please try to build this configuration (2io_slave) and test?

Cheers,

Krishna

[vicacid]

Hi Krishna,

when I select the 2io_slave configuration, the CODEC is always set as clock master (config byte is now 0x94), regardless of the value of CODEC_MASTER.

 

As this is what I want, it's certainly better than before, but I would prefer, if the behaviour is related to the configuration in the code :-) Maybe I'm just doing something wrong in the configuration of the project (project settings, debug settings, ...)?

 

What I want to do in the end is to have 8 channels audio input and 8 channels audio output with the XMOS as the clock slave. Which configuration is closest to that behaviour?

 

Thanks a lot,

Stephan

 

[krishnabalan]

Hi Stephan,

The configuration "2io_tdm8_slave" is what you are looking for.

Meanwhile following is a brief idea of the configuration structure:

In all the projects, there is a Makefile available. The #defines mentioned in the source files can be defined in the Makefile too with the option -D (i.e. -DNUM_USB_CHAN_OUT=8).  Defining an option in the makefile will be visible each and every source file of the project.  So instead of defining the CODEC_MASER in the .h files, you can put it in makefile too.  If you open the project's makefile in a text editor you can find each configuration is defined as XCC_FLAGS_<config_name>.  The required configuration defines can be put in the config's XCC_FLAGS.

If you are defining configuration in the customdefines.h file, then you must include the "devicedefines.h" file wherever you use the configuration define, For example, audiohw.xc uses the CODEC_MASTER define to change the behaviour of the CODEC and this audiohw.xc must have he #include "devicedefines.h".

Hope it helps!

Cheers,

Krishna

[vicacid]

Hi Krishna,

thanks for the explanation of the config structure. With modifications in the makefile it seems to work. 

I would like to use the 8 channels in  / 8 channels out slave mode with audio sampling frequencies up to 192 kHz. If I change the corresponding setting in the makefile to DMAX_FREQ=192000, the highest sample rate that can be played back is still 96 kHz. If I want to play back an audio file with 192 kHz, the clock on the board is set to 44,1 kHz.

Is this a limitation of the hardware or of the Thesycon-driver? Or just another config problem?

 

Thanks,

Stephan