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# AD9670 odd decimation problem

Question asked by Stef_D on Dec 20, 2016
Latest reply on Dec 23, 2016 by Stef_D

Hello,

I use the ad9670

I 'd like to decimate by 2 to 4. I do it for 2 and 4 with success. But when I try to decimate by 3, the output is always at "0" (see attached file). I can retrieve the start code but nothing else.

SPI trame (MSB Mode) : all in hexadecimal

FIR Coefficient

( Coeff for decim 2 )

700F xxxx xxxx xxxx xxxx xxxx xxxx xxxx  @1000
701F xxxx xxxx xxxx xxxx xxxx xxxx xxxx  @1010

( Coeff for decim 3 )
702F xxxx xxxx xxxx xxxx xxxx xxxx xxxx @1020
703F xxxx xxxx xxxx xxxx xxxx xxxx xxxx  @1030
704F xxxx xxxx xxxx xxxx xxxx xxxx xxxx  @1040

( Coeff for decim 4)
705F xxxx xxxx xxxx xxxx xxxx xxxx xxxx @1050
706F xxxx xxxx xxxx xxxx xxxx xxxx xxxx @1060
707F xxxx xxxx xxxx xxxx xxxx xxxx xxxx @1070
708F xxxx xxxx xxxx xxxx xxxx xxxx xxxx @1080

Vector Profl

6F07 0000 000C 8000 7FFF (decim = 2) (works)
6F0F 0000 0414 8000 7FFF (decim = 3) (failed)
6F18 0000 0A18 8000 7FFF (decim = 4) (works)

this configuration is correct? and/or the problem is somewhere else?

There is something special with odd decimation? (I tried by 5 with the same result)