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AFE5809EVM: Downconversion and Decimation in AFE5809EVM

Part Number: AFE5809EVM
Other Parts Discussed in Thread: AFE5809,

Hi,

I'm using AFE5809 Demodulator through GUI. 

I want to achieve the following:

A1. I would like to downconvert signal with 350 kHz.

We are using formula: Downconversion frequency = (N*Fs)/2^16 , where Fs is 40 MHz (onboard clock of AFE5809EVM). The value of N is thus, 573 in decimal, which is put in GUI. Is this value correct?

A2. I would like to decimate by factor of 32, so M=32 and resulting sampling would be 40/32 = 1.25 MHz. 

To do this, decimation filter coefficients has to be loaded in GUI. From page 73 of datasheet, I would have to load 256 coefficients and each coefficient is 14 bit wide. 

We have 512 coefficients in decimal for FIR filter. 

Could you please tell how to upload these coefficients in a proper way through GUI? I can email you the text file so you can have a look at those coefficients.

Thanks!

 

  • Hi Raunaq,

    We have received your inquiry and will get back to you by the end of next week. Thanks for your patience.

    Sincerely,

    Olu
  • Hi Raunaq,

    I already responded to Vatsal about how to create coefficients for the AFE5809. Page 73 of the datasheet also details how to order the coefficients depending on decimation factor.
    Please keep in mind that the coefficients are supposed to be in 2's complement format (so convert the decimal values to 14-bit 2's complement before loading the coefficients).

    Regarding using the GUI to load the coefficients, I'll try to change the filter coefficient RAM...txt file located in C:\Program Files (x86)\Texas Instruments\AFE5809EVM GUI\Scripts or use the coefficient RAM subtab of the DEMOD subtab on the AFE5809GUI.

    Sincerely,
    Olu
  • Hi Olu, thanks for the reply. Are you relating to other link in the forum regarding coefficients? Can you give more info please?

    Thanks for the confirmation regarding taking 14 bit 2's complement.  I'll change the filter coefficient RAM and will let you know if it works properly.

    Thanks!