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Data in/out format FFT IP module

Altera_Forum
Honored Contributor II
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Hello everyone! 

 

As the title of the post states we want to use the FFT IP to program it in a Stratix III FPGA but, since this is our first time with it, we have faced some problems. So far, we have managed to run the module, that is, to get the 1024 complex vector of frequencies from a sine input signal, which was generated with a NCO (numerically controlled oscillator). The problem is that the data we get at the output is not the expected for a sinewave. The fact is that we don't really know what the format of the input signal should be (two's complement for instance). We don't either know what exactly the format of the output data (vector of frequencies) is. So the question is: is it correct to connect the output of the NCO (which we DO know is in two's complement) straight to the input of the FFT module? And also, if the module's architecture is 14 bits data resolution and the output data format is fixed point format (a total of 25 output bits for the real part and another 25 for the imaginary), what would the conversion of the following binary number 1000011110111110000111100 to signed decimal format? 

 

Thank you all and any help would be apreciated!
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