Anyone with A/D designs?

[modulay]

[quote author="jdbakker"][quote author="modulay"][quote author="jdbakker"]How are you planning to support isochronous USB audio transfers with that PIC?[/quote]
By now, I'm using 4 bulk endpoints to satisfy usb-midi function and operate 2 physical midi ports.That means that I have 28 more endpoints (isochronous if needed) for audio streaming.[/quote]
Interesting.

Are you aware of this project? Do you plan to publish your usb-midi source (or have you already done so)?

JDB.[/quote]

lol
That project is a good reference to start with.
I have no plan of publish source code. It was very hard to make it work and it is mi little treasure :grin:
Anyway,midi functions are not finished at all. I still have to develope sysex data transfers functions.

[quote author="Svart"]
modulay, take a look around to see what you find. I think you should have an idea of what you need to look for. The beauty of a personal project like this is that you can try as many different parts as you want without schedule constraints! [/quote]

I've ordered also some samples of the TI PLL jdb suggested :wink:

 

[Svart]

just remember that jitter can propagate through a system from the crystal. You will still need a low jitter crystal to drive the PLL.. It might be easier to just use a clock oscillator by itself instead of using a PLL AND a crystal...

 

[modulay]

Yeah, I thought about that also.
I'm looking for some differents parts,but I'm not sure of which parameters pay atention to.
What would be a good frequency accuracy? +/-5 ppm?
What's the difference between period jitter and phase jitter?

 

[jdbakker]

[quote author="Svart"]the si530 is fixed frequency, you order the frequency you want. The si570 is ICP(in circuit programmable) via I2C.[/quote]
Right you are, I had missed that whilst spec-hunting.

[quote author="Svart"]I tried a number of XO parts and found that the si530 does a pretty nice job for the cost. Of course the difference here is that I am using LVPECL for my clocking needs and there aren't too many cost-effective solutions for LVPECL at 500mhz..[/quote]
True enough; I've been looking for LVPECL stuff myself (probably for similar reasons as you), and there's not much there except for the $$$ communications-grade oscillators. Then again, I believe that even inverted mesa crystals don't go much higher that 300MHz, so any osc block outputting 500MHz must necessarily hold more magic than a mere crystal/amp/buffer-loop.

[quote author="modulay"]What would be a good frequency accuracy? +/-5 ppm?[/quote]
Any but the cheapest crystal will do. A frequency error of 100ppm translates to a pitch shift of 0.17 cent. Know anyone who can reliably resolve that?

[quote author="modulay"]What's the difference between period jitter and phase jitter?[/quote]
Same thing, unless the author uses nonstandard terminology (which should then be specified). Jitter is the difference between actual transition times of the clock signal and ideal equidistant transitions. Phase noise is the instantaneous deviation of the clock frequency from its nominal mean value.

[quote author="modulay"]I have no plan of publish source code. It was very hard to make it work and it is mi little treasure :grin:
Anyway,midi functions are not finished at all. I still have to develope sysex data transfers functions.[/quote]
Pity, both for you and for the community. I know that the hardware/software designs I have released have always had greater returns; especially for software extra eyeballs can help you fix bugs and add useful features. But hey, your code, your decision, and I respect that.

JDB.