Re: LF: Idiot's guide to receiving Ebnaut? - Tutorial part2

[Michel Brunel <f5wk@mterrier.net>]

Andy,

Has anyone tried locking an external USB soundcard to GPS?  Chips such as the PCM290x family use their own 12MHz crystal, and it's relatively straightforward to provide 12MHz locked to some master reference like GPS to drive this.

Yes, I tried that with a Behringer UCA202 soundcard and its quite straightforward. Unfortunately the PCM290x chip has a builtin PLL to generate an internal 96 MHz clock and there is an awful PLL jitter which makes the chip unsusable for Ebnaut. 

Best to consider your PIC solution to sample and decimate the audio samples. Just wondering if the PIC16F876 I have in my junk box can be used instead of the PIC16F819 ...

Michel - f5wk

So, in theory, the 48000 and lower sampling rates will then be spot-on.  However, I fear there may be slippages in the USB interface as the 12MHz external clock, and the USB's 6MHz clock slip past each other, resulting is lost packets and corrupted data samples I do use a homebrew PCM2900 soundcard for data comms work, but never tried locking it.  Instead, for LF work I instead use the external digitiser, sending data to the PC on a RS422 interface; as described in the link sent earlier. The PIC digitiser, working on a 1kHz tone, can be used with any suitable receiver Andy  G4JNT

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