Synchronisation with audio DAC

Roland Bra

Other Parts Discussed in Thread: TMS320C5535, PCM4104, PCM4204

Hi,

I am working on a schematic for a sound card and I have a promblem with the synchronisation between DSP (TMS320C5535), ADC (PCM4204) and DAC (PCM4104).

The DSP is clocked by an 12.288 MHz oscillator (required of the bootloader). The disired system clock for the ADC and DAC shoult be 24.576 MHz to have a multiple of sampling frequencies like 32/48/96/192 kHz. (12.288 MHz would be too slow for 96/196 kHz sampling).

My plan is to use a single oscillator for both ADC and DAC, and speed up the DSP clock (multiplied by 2) after the boot frequency by the internal pll to have the same clock frequency.

Is this an option or am I on the wrong way?

Regards

Roland

over 11 years ago

0 Vasantha K over 11 years ago

TI__Genius 12575 points

Hi,

Yes, you could consider this option. Can run the sysclock at the frequency multiplied by 2(as mentioned by you) .

Hope this helps.

Regards

Vasanth

0 Roland Bra over 11 years ago in reply to Vasantha K

Prodigy 160 points

Ok, I thought about that too. But in the data sheet is written for CLKOUT "DSP clock output signal. For debug purposes only..."

Seems like this pin should not be used to drive other components or would this be ok?

Thank you for your response.

0 Vasantha K over 11 years ago in reply to Roland Bra

TI__Genius 12575 points

The datasheet is correct. The clock out should only be used for debug purpose and it should not be used for driving other components.

Correction. I only meant from driving C5535 peripheral outputs point of view. If you are to use clock out for driving other components then this is not suggested.

Regards

Vasanth

0 Vasantha K over 11 years ago in reply to Vasantha K

TI__Genius 12575 points

Not sure whether you have an option of external oscillator, if so control the ADC directly with the external oscillator, and in this case DSP becomes slave (I2S interface).

Also below wiki link may be useful reference for ADC clocking schemes.

Audio Serial Interface Configurations for Audio Codecs - SLAA469

Regards

Vasanth

0 Roland Bra over 11 years ago in reply to Vasantha K

Prodigy 160 points

Ok, after reading the SLAA469 it seems to me like that the only option is to use an 12.288MHz-oscillator. This will be the master clock for DSP, ADC and DAC. In this case the sample frequenzies 96 and 192 kHz could not be realised.

Even if the DSP becomes slave, a shared 24.576MHz-clock which is required for those high sample rates can't be used. Otherwise the DSP-bootloader will not work correctly.

Regards

Roland

0 Roland Bra over 10 years ago in reply to Roland Bra

Prodigy 160 points

...forgot to share my workaround: I used a single oszillator for DSP, ADC and DAC and placed a D-Flip-Flop between the oszillator and the DSP to devide the frequenzy by 2 for getting the 12.288MHz wich the DSP-bootloader required.

Regards
Roland

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Synchronisation with audio DAC