DC output altera data conversion card

Question

Hi All,

I using the card cyclone iii fpga development kit starter (https://www.altera.com/products/boards_and_kits/dev-kits/altera/kit-cyc3-starter.html) with the cyclone iii data conversion hsmc (https://www.altera.com/products/boards_and_kits/dev-kits/altera/kit-cyc3-dsp.html).

I'm trying to create a simple square wave of 1 and -1.

But the DAC does not create the wave it makes a wave that looks as a charging and discharging of a capacitor,

or a spike instead of a long peried of a "1".

Do you have examples of creating such a wave?

I can make a sine wave, could it be wrong data that i'm sending (offset binary?) ?

Thanks in advance :)

altera_forum · Answer

Are you probing the analong signal directly on DAC output pin?

I guess that data conversion daughterboard is supposed to generate audio outputs which are usually AC coupled; if you test the signal after the final audio stage you'd get waveforms similar to those you describe

altera_forum · Answer

i'm probing the bnc (is it called sma?) out connector / RF out. I'm trying to create the square wave, not using the audio, did anyone try?

altera_forum · Answer

The data conversion card uses output transformers which act as a band pass filter. And DC component to a signal will be removed. If the frequency of the square wave is too low it will appear as DC for some of the time so the transformers will saturate and you will get a strange sort of sawtooth.

There is no way of producing DC from these boards. Nor any way of producing a low frequency square wave.

altera_forum · Answer

Ok, thanks!  Can you suggest a solution? A circuit / other component that can generate the signal?

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DC output altera data conversion card

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