[Dprglist] OK to jumper XTAL OSC together?

Doug Paradis paradug at gmail.com
Tue Dec 17 15:21:14 PST 2019

    Can you take a photo or give the product @ of the boards?

Doug P.

On Tue, Dec 17, 2019 at 2:57 PM John Swindle via DPRGlist <
dprglist at lists.dprg.org> wrote:

> Folks:
> I always enjoy the DPRG meetings and competitions, and last week was great!
> I have a question regarding my sonar project:
> I'm using two cheap USB audio adaptors to measure the sound. The samples
> have to be very tightly synchronized. Each adaptor has its own 12MHz
> crystal oscillator as an external component on the PCB. I wonder if I can
> jumper one crystal to the other without damaging the clock driver.
> I don't have the schematic. SIIG and VANTEC make the adaptor which uses
> the C-Media CM6206 containing audio DACs and ADCs.
> A better approach is to use a TI, Analog Devices, or Maxim multi-channel
> simultaneous sampling ADC, and I plan to buy a TI evaluation board.
> Another better solution is to use a multi-channel pro audio mixer/adaptor.
> I have one of those, but TASCAM stopped supporting mine a few months after
> I bought it, and the driver crashes Windows 10. Also, even if I got a newer
> adaptor, it would be much larger, physically, than what I want on a robot.
> OK for prototyping, but not good for demonstrations.
> I've closely synchronized the adaptors by having one of them give a click
> track to the other one. The software resamples the second adaptor's samples
> based on errors in the recorded click track. The click track software does
> a good job of handling the persistent difference in the two oscillator
> frequencies, but I have not added code to handle jitter. A hardware
> solution would be more like what the final solution looks like.
> (While writing that software, I realized that the click track just forces
> the second adaptor to suffer the first adaptor's jitter, meaning I have not
> eliminated jitter. Nevertheless, the results are nearly pristine for all of
> the ADCs within an adaptor which are jittering together, so if I get the
> ADC in the other adaptor to jitter with the first one, the results would
> probably be very good.)
> Best to y'all! See you next year.
> John Swindle
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