[time-nuts] WWVB BPSK Receiver Project? (fwd)

[Attila Kinali]

Moin!

On Fri, 16 Mar 2012 07:09:05 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> In message <20120315234624.a2da94430a247d235ca68b4f at kinali.ch>, Attila Kinali writes:

> >On the other hand, if you dont have to support an OS and work on the
> >bare metal, you can get away with very little RAM. 128k is a damn lot
> >if you have to fill it with usefull data structures ;-)
> 
> Well, if you want to do full-FRI averaging for a loran-chain, you need
> something like 99600*2 * 4 = 800Kb.  If you want to do the full-hour
> averaging the WWVB doc talks about or DCF77 full-second phase-code,
> you need 2 MB for just the buffer.

Hmm... do you mean you want to store all samples of an hour and then
avarage over it? I think it would be better to just store phase offset
points for every second and then avarage over this. That would require
much less storage.

 
> >> USB2 interface 
> >
> >Which would mean you need a pretty recent chip as HighSpeed USB has not
> >been introduced into the uC world for more than 2 years or so.
> 
> USB2, not USB3.

I'm not talking about SuperSpeed. USB2 support has been around for
quite some time in ARM7 class uC. But USB2 does not mean you support
a certain speed, just the data structures follow the revised standard.
Yes, USB2 introduced the HighSpeed mode (the 480Mbit/s), but below
ARM9/MIPS class CPUs it wasn't supported until about 2-3 years ago.
AFAIK the Atmel SAM3U was one of the first Cortex-M3 with HighSpeed
support available in volumes... and that was IIRC late 2009, early 2010.

And the number of uC's with HighSpeed support isn't that large yet.


			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin