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PSoC 5, 3 & 1

Anonymous
Not applicable

Hello,

   

Very new to these forums.  I am evaluatinG gthe PSoC3 on the CY8CKIT-030 platform and I was wondering what the maximum frequency I can get out of the WaveDac8?

   

Out of the box the best I can do is 2.5khz, but I see an external clock.  I have also done some work with other PSoC's and know there are some internal clock settings so I am hoping there is something else I can do.  I am looking to get 50khz@1.5vp/p

   

 

   

Is this attainable?

   

 

   

Thank You

   

Jim

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7 Replies
Bob_Marlowe
Expert II

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.

   

 

   

Bob

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EvPa_264126
Valued Contributor II

 Judging from the documentation:

   
    sample rate 1Msps    for  0-1.024V mode   
   
    sample rate 250ksps  for  0-4.096V mode   
   
        
   
    also:   
   
     How to make DDS module   
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ETRO_SSN583
Esteemed Contributor

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 -

   

 

   

   

 

   

Regards, Dana.

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ETRO_SSN583
Esteemed Contributor

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

   

 

   

 

   

Regards, Dana.

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Anonymous
Not applicable

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.

   

 

   

Regards,

   

Jim

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ETRO_SSN583
Esteemed Contributor

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

   

 

   

Regards, Dana.

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Anonymous
Not applicable

Great link, Thanks!

   

 

   

Jim

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