PCM2906C: SPDIF to USB converter

Shall reply by 08/23

Hi,

PCM2906 supports 3.3-V CMOS-level input as SPDIF input with internal pulldown. Please check the SPDIF OUT level of the ADAU1452 chip for compatibility with respect to logic level, drive and ground. Grounds of the two EVMs should be tied together.

Also please note the following data formats accepted by S/PDIF for input and output. All other data formats are unusable as S/PDIF.

• 48-kHz 16-bit stereo

• 44.1-kHz 16-bit stereo

• 32-kHz 16-bit stereo

Mismatch between the input data format and the host command may cause unexpected results, with the following exceptions:

• Recording in monaural format from stereo data input at the same data rate

• Recording in 8-bit format from 16-bit data input at the same data rate

A combination of the two foregoing conditions is not accepted.

For playback, all possible data-rate sources are converted to the 16-bit stereo format at the same source data rate.

Regards,

Sakshi

Hi,

I verified everything you mentioned above.  I see the output from my ADAU1452 EVM (blue board) as an encoded waveform with a 3.3V logic level.  I am simply outputting a 500Hz sine wave on both channels of the SPDIF output.  The output of the SPDIF out is connected to pin 3 of CN002 (which is connected to DIN of the PCM2906C) and GND of the ADAU1452 EVM is connected to pin 2 of CN002 (which is connected to GND).  Additionally, I verified my SPDIF output is formatted as 48kHz 16-bit, yet I still do not see any signal in Audacity.  As I mentioned I verified this signal driving an analog input to the PCM2906 module, so I know my set up to the computer is valid.  I  even tried restarting the Audacity application with no luck.

Hi,

The issue could be related to Audacity setup.

Please ensure if the SPDIF input shows up in the Windows Sound control panel?
If it does, do you see any activity in the recording level meter when you input a signal through SPDIF? If yes, set the Audacity Preferences to 48000, 16-bit Stereo. These are not Audacity default settings. Restart Audacity after you change the settings.

Regards,

Sakshi

Hi,

I changed the settings in audacity to allow for 48000 16 bit stereo but I am still seeing no output in Audacity.   

Do you see activity in the recording level meter when you input a signal through SPDIF?

No I do not see any activity. I don't see any option for 'SPDIF input" on my computer under the recording tab.  As you see, there's only 'Line" which is the USB audio codec PCM2906 EVM

Request you to please verify the S/PDIF input and S/PDIF output by probing the waveforms seen on pin 24 & 25 respectively of PCM2906C IC.

Hi  - here is the waveform you requested

Yellow is the output from my ADAU1452 and blue is what the PCM2906 is outputting on SPDIF.  Both probed at pins 1 and 3 of CN002

Also I just verified if I reverse the direction of audio I can  send audio from my PC -> PCM2906C EVM -> ADAU1452 EVM via SPDIF (pin 1 on CN002), and  I can successfully monitor the signal with the on-board headphone output of the ADAU1452 EVM.  I'm not sure why i'm getting no output whatsoever when trying to get SPDIF into the PCM2906C with a seemingly valid waveform

Hi - is there any special configuration I need to set on the output side of my ADAU1452 SPDIF settings?

Can you advise if I need to set the Channel Status or Validity bits, and if so, what they should be?

Edit: I've tried both 24 bit and 16 bit settings for the 'audio word length', but neither worked

Thanks

Greg