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configure multi channel McBSP

Rong Wang
Prodigy 70 points

Hi,

 

 I will need to connect two codec to McBSP0 on C5410A DSP. I am confused by number of channels and number of time slots when data size is not 8 bits. since 16 bit data will take two 8 bit time slots of the TDM bus. I wonder when I want to enable a 16 bit channles, I should enable two time slots or just the first one?

For instance,

 
>
> if XMCM =01,PHASE=0, XFRLEN =0, XWDLEN =010b, and I want to enable a 16 bit
> channel, say channel 1, I should set XCERA = 3(enable time slot 0 and 1)
> or just set XCERA = 1  ?

Thanks in advance.

Ron
  • 0
    TI__Expert 7290 points

    Hi Rong,

    Basically each channel has its own 'n' number of time slots and each time slot can be configured for 8 bit, 16 bit .... 32 bit depending on the McBSP (refer McBSP data sheet). So my suggestion would be to configure the XWDLEN in such a way that each slot is of 16 bit.

    Let me know the result.

    Thanks and Regards,

    Sandeep K

  • 0 in reply to Sandeep Krishnaswamy
    Prodigy 70 points

    Hi Sandeep,

     

    Thank you very much for your reply!

     

    As you see from my configuration, I did set word size to 16 bits, number of frame to 8, and in RECRA and XCERA, I enabled two 8 bits time slot for each 16 bits channel. for instance, I set  RECA0  and RECA1 for my first 16 bits channel 0. To enable 16 bits channel 0, I should set both of RECA0 and RECA1 or just RECA0?  I actually tried both, none of them works.

    If I use ulaw companding in both McBSP0 and codec, it works well. but if I use 16 bit linear data, it did not work. To use 16 bit linear data, the changes I made is:

    • configured codec to 16 bits data size, and receive/send data at time slot 0,2,4,6,8,10,12,14( the codec is Zarlink's Le58QL02FJC).
    • in McBSP, I changed word size to 16 bits, no companding with MSB first, number of word per frame is still 7(channel 3 is not used). In RECA and XCERA, I set two slots for one channel.
    • the FSR and FSX from external(from FPGA) at 8kHz.

      My another question is:  does it really matter for number of words per frame as long as the number is more than the number of actually channels used since the FSR/FSX is fixed.  In my case, I set  number of word per frame to 8. I mean if I set number of word per frame to any number between 8 and 16, it should work as well?

    Thanks,

     

    Ron

  • 0 in reply to Rong Wang
    Prodigy 70 points

    Solved.

    Realized that just need to set one RECAn and XCEAn regardless of the size of word. after this correction. it works.

     

    Thanks,

     

    Ron