[time-nuts] DDS'ery

dk4xp at arcor.de dk4xp at arcor.de
Tue Jun 21 13:14:38 UTC 2011


 There is an excellent article about cordic on 

     http://www.andraka.com/files/crdcsrvy.pdf

There are a lot of other good publications on Ray Andraka's
web site.

I have published a accurate sine/cosine function on www.opencores.org
under    http://opencores.org/project,sincos
It is VHDL only. The test bed is a DDS and it can write the generated waves
to files for inspection with Matlab. 
I think I have caught all these off-by-1-LSBs by now.

The sine function is ROM-based with size reduction by symmetry.
Getting a cos at the same time is free wrt ROMs, just 2 adders more.
Pipelining can be selected from combinatorial to 10 stages, depending
on your speed requirements. Amplitude and phase resolution is
automatically determined by the connected bus.

feedback welcome.

regards, Gerhard






----- Original Nachricht ----
Von:     lists at lazygranch.com
An:      Discussion of precise time and frequency measurement <time-nuts at febo.com>
Datum:   20.06.2011 22:26
Betreff: Re: [time-nuts] DDS'ery

> With the coordic (yeah, sometimes cordic), you need to build it a few more
> bits wider than the DAC. Then it closely matches the lookup table. One of
> the best references for the coordic I found was a PhD dissertation at
>




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