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ADC3101 Supported USB Sampling Rates ?

Chris Nielsen
Intellectual 605 points

I'm seeing very poor quality PCM samples when programming the ADC3101 EVM for 16 KHz.  I worked on this evm a few years ago and I remember needing to get a special factory EEROM update to allow the evm to work at my sampling rate.  It may have been 8 KHz at the time.  The document only mentions 44.1 KHz as a nominal sampling rate for filter work.

Can you share the supported sampling rates and any upgrades for new sampling rates that might be available?

I only need 16 KHz operation right now.

Thanks, Chris

  • 0
    Intellectual 605 points

    I may have found it.  I appear to be getting much better results at 48 KHz then downsampling to 16 KHz in my software (because I require 16 KHz).  There's a common phenomenon in the "sound card" industry and 44.1 and 48 KHz are usually the only safe sampling rates (most likely to be accurate).  I've seen a lot of poor results deviating from these.  I forgot this "rule" but eventually remembered it.  It would be helpful to have this confirmed.  Thanks, Chris

  • 0 in reply to Chris Nielsen
    TI__Mastermind 28585 points

    The ADC3101 will support a wide range of sample rates. The EVM is set up to run at 44.1 kHz. The issue is that the USB to I2S controller we use is set to run at 44.1 kHz and takes a firmware load to change. The best solution is to use an external I2S source when testing at other sample rates. You are correct that most PC audio cards are either 44.1 or 48 and play games to achieve other rates.

  • 0 in reply to Converter Apps
    Intellectual 605 points

    Excellent.  Progress.  It would be REALLY helpful to get a firmware load so I can get good samples over USB at 16 KHz.  Is this possible?  Thanks, Chris

  • 0 in reply to Chris Nielsen
    TI__Mastermind 28585 points

    If you have the latest version of the EVM software from the web, you have it. When you launch the software, go the "Tools" prompt and click the +. You will see "EEPROM Writer". Click that and follow the instructions. Should work fine.

  • 0 in reply to Converter Apps
    Intellectual 605 points

    It works like a champ now.  Thanks for the help.  (a heads-up, after burning new firmware, must apply ratio = (new rate / 44.1) * 11.2896 on-board MCLK.  in my case of 16 KHz, my new MCLK is now 4.096 MHz)