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Altera_Forum's avatar
Altera_Forum
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17 years ago

Streaming FFT design - version 8.1

Hi,

I have utilized the megacore function within Quartus II to generate a design for a 512-point FFT. I successfully verifyied the fft engine with ModelSim and compared the results with Matlab. However when I integrate it with the FFT control, I run into several problems which have stumped me :(

I am attaching a screenshot which shows my simulation results. Just to summarize, I am able to generate and transmit the sink_sop, sink_eop, sink_valid all when sink_ready is high. However the fft engine does no computation and does not spit out any results (this includes the source_sop/eop, source_valid, source_error etc). All the output signals are low.

I assume that the FFT engine will carry out its computation when the following are true:

1. Clock enable is high

2. Sink_valid is high only when sink_ready is high

Is there something I am missing?

Any help would be much appreciated.

Thanks!

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    The fft control state machine was written in a way so you can use the variable streaming architecture in a burst-like format. If you want to use it with regular streaming, make sure you set the pulse between frame to zero (there is a parameter that you can set)...

    Also keep in mind that there is usually about a 2.5-3 frames worth of delay between input and output... You have only simulated long enough to input one input packet... I imagine if you simulate a bit longer (at least 3 times longer), then you should see the first output packet coming out of the FFT core...
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Wronghorizon, thanks a million! That seems to have worked :)

    And thanksonce again for the FFT_control too!