SK-AM62: Detecting External Clock Supply on McASP0

Tool/software:

I would like to detect the supply of an external clock on McASP0.
I’m implementing this based on the sample located at:
C:\ti\mcu_plus_sdk_am62x_10_01_00_33\examples\drivers\mcasp\mcasp_playback_codec_aic31.

Although I’ve read the documentation (see page 1073 of www.ti.com/.../spruiv7b.pdf), I couldn’t figure out how to achieve this.

Specifically, I want to implement the following four functions:

1. Detect when the external clock is supplied for the first time (initially not supplied).
2. Detect when the external clock stops.
3. Detect when the external clock is supplied again.
4. Once the external clock is detected, restart McASP and output to the speaker.

This is related to the following thread:
e2e.ti.com/.../sk-am62-how-to-properly-restart-mcasp0-after-calling-mcasp_close

If possible, I’d appreciate guidance based on source code.

What I’ve tried so far (for reference):

 Working:

• Syscfg is configured to receive clock from AUDIO_EXT_ERFCLK1.
• Audio output works when the clock is supplied from AUDIO_EXT_ERFCLK1.
• If Drivers_mcaspOpen() is called beforehand, the initial clock detection works.

 Not working:

• The logic for initial clock detection seems incorrect.
• Behavior of Drivers_mcaspOpen() and Drivers_mcaspClose() is problematic.

 Steps I’ve tried for clock detection: (Assuming no external clock is supplied initially)

1. Call Drivers_mcaspOpen()
2. An error occurs but I continue processing:
   ERROR: Drivers_mcaspOpen:295: MCASP open failed for instance 0 !!!
3. Initialize based on documentation:
   

   void init_mcasp0_rclkchk()
   {
       uint32_t val = CSL_REG32_RD(MCASP0_RCLKCHK);
       val &= ((0x00 << 16) | (0x00 << 8));
       val |= (RCKCHK_MAX << 16);
       val |= (RCKCHK_MIN << 8);
       val |= (2 << 0);
       CSL_REG32_WR(MCASP0_RCLKCHK, val);
       CSL_REG32_FINS((CSL_MCASP0_CFG_BASE + MCASP_RSTAT_OFFSET), MCASP_RSTAT_RCKFAIL, 1u);
   }
   

4. Check MCASP0_RCNT and RCKFAIL:
   

   void chk_mcasp0_rcnt()
   {
       uint32_t rcnt = (CSL_REG32_RD(MCASP0_RCLKCHK) >> 24) & 0xFF;
       uint32_t rmax = (CSL_REG32_RD(MCASP0_RCLKCHK) >> 16) & 0xFF;
       uint32_t rmin = (CSL_REG32_RD(MCASP0_RCLKCHK) >> 8) & 0xFF;
       DebugP_log("[MCASP0]RCNT: %3u | RMAX: %3u | RMIN: %3u\r\n", rcnt, rmax, rmin);
   }
   
   bool poll_mcasp0_rckfail()
   {
       uint32_t isFail = CSL_REG32_FEXT((CSL_MCASP0_CFG_BASE + MCASP_RSTAT_OFFSET), MCASP_RSTAT_RCKFAIL);
       if (isFail == CSL_MCASP_RSTAT_RCKFAIL_YES)
       {
           DebugP_log("RCKFAIL: clock NG\r\n");
           CSL_REG32_FINS((CSL_MCASP0_CFG_BASE + MCASP_RSTAT_OFFSET), MCASP_RSTAT_RCKFAIL, 1u);
           return false;
       }
       else if (isFail == CSL_MCASP_RSTAT_RCKFAIL_NO)
       {
           DebugP_log("clock OK\r\n");
           return true;
       }
       else {
           DebugP_log("ERROR!!　%d\r\n", isFail);
           return false;
       }
   }
   

5. Supply external clock
6. poll_mcasp0_rckfail() returns true
7. Drivers_mcaspOpen() fails, but after calling Drivers_mcaspClose() and reopening, it succeeds
8. Re-run init_mcasp0_rclkchk()
9. Call MCASP_startTransferRx() / MCASP_startTransferTx() → speaker output works
10. Stop external clock
11. poll_mcasp0_rckfail() detects clock stop
12. Stop McASP as per documentation (MCASP_stopTransferRx, MCASP_stopTransferTx, MCASP_withdrawRx, MCASP_withdrawTx)
13. Re-run init_mcasp0_rclkchk()
14. External clock is not detected again
15. Calling Drivers_mcaspClose() / Drivers_mcaspOpen() causes the program to hang