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Distorted sine wave, NCO v11.1

Altera_Forum
Honored Contributor II
‎02-25-2015 12:02 PM
1,220 Views

Hi, 

 

I have NCO v11.1, Stratix II, EP2S180F1020C3, Quartus II 32-bit Full Version 11.1. 

The shape of the generated sine wave (viewed on the oscilloscope) 

is distorted more or less, depending on the compilation.  

About every ten compilation sine wave looks correct.  

The differences in design between the builds are not associated with the NCO.  

Generated by the NCO waveform has the desired period.  

large rom or cordic Generation Algorithm used, 100MHz clock rate, global. 

The new value given to phi_inc_i at a rate of at 2us. 

The only remedy is an upgrade? 

 

FPGA_user3
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Altera_Forum
Honored Contributor II
‎05-04-2015 09:12 AM
288 Views

When you generated the Code from NCO.. How did you tested the Code ?. Do you have a DAC on your Board. How did you saw the result on Oscillioscope ? Can you please clarify.

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Altera_Forum
Honored Contributor II
‎05-05-2015 09:17 PM
288 Views

Are you sure that all signals fed to the NCO, e.g. phi_inc_i are keeping timing constraints? Ho do you generate the timing of all input signals?

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