[time-nuts] Slightly OT: inexpensiveUSB analog-digitalconverter?

[Ulrich Bangert]

Darrel,

I know the situation pretty well: You may have developed something for
some purpose without even knowing what perfect tool it is for something
completely different.

Without even knowing the technical details of your design it sounds to
me that two of your boards with a bunch of software that needs to be
written would team up to an oscillator characterization device that may
come close to the best industrial devices available in terms of
performance.

Can you share some more detailed information about your project with us?

73 de Ulrich, DF6JB 
 

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Darrell Harmon
> Gesendet: Donnerstag, 17. Januar 2008 05:11
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Slightly OT: inexpensiveUSB 
> analog-digitalconverter?
> 
> 
> John Miles wrote:
> > Is it just me, or is there a huge hole in the DAQ marketplace for a 
> > high-resolution, low-noise, low-to-moderate cost, _medium_-speed 
> > acquisition dongle?
> >
> > I've been planning to build a 100+ dB 24-bit USB DAQ 
> interface around 
> > the AD7760 for some time now, which would be good from DC-1 
> MHz.  That 
> > would be something like having a high-end sound card input with a 
> > 2.5-megasample ADC instead of an audio ADC.
> >
> > The only thing that's stopped me so far is the FPGA and USB 
> > interfacing work...
> >
> > -- john, KE5FX
> >   
> I would certainly consider building one if you designed it and made 
> gerber files or boards available.
> 
> I am currently finishing up a project with a 125 MHz 16 bit 
> ADC and an 
> FPGA digital down converter. The output rate is similar to what you 
> would have (32 bit IQ at 500 kHz, so 4 MB/s). This does not seem very 
> difficult with USB 2.0, but actually is quite difficult. I did 3 
> revisions of my board. The ADC and FPGA worked perfectly on the first 
> revision, and the second two revisions were due to USB interface 
> problems. I tried the Cypress FX2 and had nothing but 
> problems with it. 
> I am now using a Blackfin DSP and PLX NET2272 USB chip as the PC 
> interface. It works well. I have written a spectrum analyzer 
> application 
> for it and plan on doing some software defined radio work 
> with it soon.
> 
> Whatever you do, it would be best if the sampling rate could 
> be locked 
> to an external 10 MHz input. I did that with my board and expect to 
> write software in the next few months for frequency measurement.
> 
> Darrell Harmon, KI4MVK
> 
> 
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