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Suspending McASP MCLK

Don Hardebeck
Prodigy 40 points
Other Parts Discussed in Thread: TMS320C6745, TLV320AIC3007

We have a medical device which uses the TMS320C6745 DSP.  The device also contains a Telit chip for cell communications which we are upgrading to a newer chip.  With the newer cell chip and antenna, we noticed that we now have spurious signals from the McASP MCLK. connected to a TLV320AIC3007 codec which degrades the cell signal.  The McASP is configured and initialized in the power on sequence.  However, we don't need the audio when transmitting data via the cell chip, so we would like to turnoff the MCLK while transmitting and then turn it back on when done.  We have a hardware solution but prefer to do this in software.  Is this something that can be done and if so how? 

  • 0
    TI__Guru**** 161600 points
    Hi,

    I've notified the RTOS team. They will post their feedback directly here.

    Can you share which RTOS SDK version are you using?

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Prodigy 40 points

    My DSP/BIOS version is 5.42.109 and I am using version 5.5.0.00077 of Code Composer.

  • 0 in reply to Don Hardebeck
    TI__Mastermind 30170 points
    Hi Don,

    Sorry your question went unanswered for so long. Did you find a way to stop the MCLK in software?
    Could you try performing the init sequence as documented in section 24.0.21.1.2 Transmit/Receive Section Initialization in the in TRM (SPRUH91) more or less in reverse? I advise you to stop the high-frequency serial clocks AHCLKX and/or AHCLKR (MCLK) towards the end of the clock stopping sequence - after all the serializers are stopped. This is because the state machine is clocked by these high-frequency clocks.

    Regards,
    Mark
  • 0 in reply to Mark M
    Prodigy 40 points

    I ended up taking a different approach.  The interference in the antenna is primarily from the trace on the PCB from the DSP to the codec.  In lieu of shutting down the clock, I reconfigured the pin from a McASP to a GPIO low output before attempting a cell transmission.  This seems to work.  We can reinitialize the McASP after the cell transmission is complete, however, we would prefer to just reconfigure the pin back to McASP afterwards.  Do you see an issue with this approach?

  • 0 in reply to Don Hardebeck
    TI__Mastermind 30170 points
    No issue. As long as the AHCLKX/R is still running internally (even if the pin is pinmuxed as a GPIO), then the McASP state machine will continue to run.

    Regards,
    Mark