• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 98 subscribers
  • Views 388 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

McBSP Transmit channel swap

sachinpdesai
Intellectual 1260 points
Other Parts Discussed in Thread: DM3730

I am using BIOS PSP for DM3730. The transmit is set  to output two channels. We observe that for some runs the channels are swapped (Left channel data going to right speaker and vice-versa).  How can we debug this?

regards

Sachin

  • 0
    TI__Intellectual 1260 points

    The BIOS PSP I am using is 1.30.01. The sampling rate is 48kHz.

  • 0 in reply to sachinpdesai
    TI__Expert 7290 points

    Sachin,

    The reasons for channel swap could be,

    1. If the computed size does not match the logical end of channels, the channels could be swapped.

    2. If the McBSP is sending out the data on rising edge and the data is sampled at falling edge at the other end.

    3. If the EDMA is disabled and then re-enabled while EDMA transaction is going on. Eg: If the EDMA is reset Just after sending the left data, then the left data of the next packet will be treated as the right data. So the channel swap.

    Please check these points and let me know.

    Regards,

    Sandeep K

  • 0 in reply to Sandeep Krishnaswamy
    TI__Intellectual 1260 points

    Hi Sandeep,

      The case turned out to be little more convoluted. The OMAP3 McBSP has to bits to start transmission, one in SPCR register and one in XCCR register. I had to modify to do the following

    1) enable the bit in SPCR

    2) Start EDMA

    3) wait 1 ms ( I do not know how valid this is, but ALSA has this set to 500 us)

    4) enable the bit in XCCR.