Sample rate in BF-533

Hi everybody,

I'm working in a speech project with the ADSP Bf-533 EZ-KIT LITE, and I have some problems with the sample rate. I need to get a slower sample rate in order to avoid aliasing in the input signal. I know that AD1836 only has two options (48Khz and 96Khz). I'm using the Serial Port to read the data and DMA to store the samples. How can I reduce the sample rate to, for example, 18Khz?

Thank you very much Start a New Thread

It would be easier to reduce sampling rate to 24 or 19.2 kHz by decimating the 96 kHz stream either by 4 or by 5. Blackfin DSP library has a function, fir_decima, that implements an FIR decimator. However, I've never used it on practice and not aware if it has any limitations on block processing. I think that someone else in this group can tell you more about its applications.
In order to obtain 18 kHz sample rate You'll have to interpolate 48 kHz sample stream by 3 and decimate it by 8. In fact it can be accomplished with a single properly designed filter.

--
Alexander

Hi everybody,
>
>I'm working in a speech project with the ADSP Bf-533 EZ-KIT LITE, and I have some problems with the sample rate. I need to get a slower sample rate in order to avoid aliasing in the input signal. I know that AD1836 only has two options (48Khz and 96Khz). I'm using the Serial Port to read the data and DMA to store the samples. How can I reduce the sample rate to, for example, 18Khz?
>
>Thank you very much Start a New Thread

Set the 12LSbits of ADC_CONTROL_3 to 0x040 for 24kHz or 0x080 for 16kHz. These are the only other sampling freqs apart from 96kHz and 48kHz that the 1836 CODEC runs at.
God Luck
Professor Anthony J.A.Oxtoby
Knoy Hall of Technology
401 N Grant Street
West Lafayette
IN 47907-2021

Expect Less and Never be Disappointed
Expect More and be Surprised!

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Subject: [adsp] Sample rate in BF-533

Hi everybody,

I'm working in a speech project with the ADSP Bf-533 EZ-KIT LITE, and I have some problems with the sample rate. I need to get a slower sample rate in order to avoid aliasing in the input signal. I know that AD1836 only has two options (48Khz and 96Khz). I'm using the Serial Port to read the data and DMA to store the samples. How can I reduce the sample rate to, for example, 18Khz?

Thank you very much Start a New Thread

Thank you very much for all the answers. They have been very useful... Start a New Thread