AM2732: AM2732: How do I switch the clock source for an MCASP instance in my application?

Xiang Zhao

Part Number: AM2732

However, the AM273x Technical Reference Manual does not mention any "glitch-free switching between the local and system AUXCLK source" mechanism, unlike what appears to be available on AM275x.

My question: What is the recommended procedure to switch the MCASP clock source at runtime on AM2732?

Specifically, I would like to know:

Does the AM2732 clock mux for MCASP support glitch-free switching, or must the MCASP be stopped before changing the clock source?
If a stop-reconfigure-restart sequence is required, what is the correct order of operations to avoid DMA descriptor corruption or audio buffer data loss?
Are there any application notes or SDK examples targeting AM2732 that demonstrate this use case?

Any guidance or pointers to relevant documentation would be appreciated.

5 months ago

0 Ritapravo Sarker 5 months ago

TI__Genius 14435 points

Hi Xiang,

I will have to check if the glitchfree clock switch mux is available in am2732. Give me some time. I will check and get back to you.

Regards,
Ritapravo

0 Ritapravo Sarker 4 months ago in reply to Ritapravo Sarker

TI__Genius 14435 points

Hi Xiang,

Thanks for your patience and apologies for the delay. I was out of office for a few days.

Xiang Zhao said:
Does the AM2732 clock mux for MCASP support glitch-free switching, or must the MCASP be stopped before changing the clock source?

Yes, there is a GCM in am2732 also. I am attaching a document regarding this -

AM273_GCM.pptx

Xiang Zhao said:
Are there any application notes or SDK examples targeting AM2732 that demonstrate this use case?

There is no SDK example for this. I will quickly look thorugh other documentations if there are more information on this.

Regards,
Ritapravo

0 Ritapravo Sarker 4 months ago in reply to Ritapravo Sarker

TI__Genius 14435 points

Hi Xiang,

There are few more threads regarding this in the HARMAN forum -

MCU-PLUS-SDK-AM273X: Using GCM for clock switch

RE: MCU-PLUS-SDK-AM273X: Forcing GCM clock source switch

530-23456 Documentation for AM273x Glitchless Clock Mux (GCM), usage for McASP on the fly clock source switching

Let me know if you are able to access this or need any more info on this.

Regards,
Ritapravo

0 Xiang Zhao 4 months ago in reply to Ritapravo Sarker

Prodigy 10 points

Hi Ritapravo Sarker

Thank you for your response and detail info.

It appears the slide you shared assumes McASP operates as the TDM clock provider, and describes how to switch the clock source accordingly.

In our design, McASP initially acts as the TDM clock provider at startup to bring up the audio tasks.

Once the external A2B clock becomes available, McASP must transition to clock receiver mode, with the TDM frame sync (FS) and bit clock (BCLK) sourced from A2B FS&BCLK directly.

In this case,

could you advise how to achieve a smooth clock switching?

Specifically, how should McASP transition from clock provider to clock receiver (driven by A2B FS and BCLK) without causing audio glitches or DMA transfer errors during the switch?

Best Regards,

Zhao, Xiang

0 Erik Friedel 4 months ago in reply to Xiang Zhao

TI__Expert 8405 points

Xiang,

I am going to close this thread and redirect here: AM2732: AM273x McASP + A2B clock switching: DMA interrupt/frame alignment drift after repeated A2B connect/disconnect

The topic and questions are largely the same.

Regards,

Erik

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AM2732: AM2732: How do I switch the clock source for an MCASP instance in my application?