Internal to the WaveDAC is a table for the output function. This table is red from a DMA channel and transferred to the DAC.
To have a high output frequency you can
Increase the clock for WaveDac
Decrease the table size.(will reduce the precision of the wave)
Increase the IMO clock frequency to its maximum (will affect the DMA)
Obviously some tests are needed to find the right balance.
Use your DSO, FFT, alter the number of samples in the
configurator and examine the harmonic response. Its
surprising how low you can go in the sine table, # samples,
and still get fairly good harmonic distortion numbers. Primary
limitation on DDS frequency operation is VDAC settling time.
The table size and clock rate control frquency -
Here are some alternative possibilities for sinewave generation,
but still limited by Vdac settling time. Could use the MAC in DFB.
http://www.cypress.com/?app=forum&id=2492&rID=87059 Sinewave Generation
Thanks all for the suggestions.
I did see that making some changes I can get teh 50khz, but it is stairstepped(expected). I will put this signal through a bandpass filter and see how well it cleans up.
I have played with teh external clock, but I am limited to how fast teh DAC can go so it's a game getting things the way I want.
I will look at the DDS as well.
For filtering a wavedac LPF will work fine.
If you want a single freq sine certainly using a BPF
on just a squarewave will extract fundamental. Use
Sallen and Key solution with internal OPamp.
A tool to make it easy - sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm
Great link, Thanks!