PSoC5lp Band Pass Filter

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Anonymous
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Hey guys,

   

I just came across this article

   

http://www.cypress.com/knowledge-base-article/frequency-limits-low-pass-filter-and-bandpass-filter-u...

   

 

   

I was using the filter blocks in the PSoC creator. I wasn't able to achieve a band pass filter above 10KHz. Can someone give a sample code for higher frequency, if possible the limit as mentioned 250KHz.

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Bob_Marlowe
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Welcome in the forum

   

You only need a realistic sample rate to perform your filter. Nyquist is 2f, but I suggest 10 to 50f gives the best results.

   

250kHz * 20 is 5MHz sample rate which is a bit fast for the ADC. At 20kHz you would be fine off with a sample rate of 400kHz.

   

I would suggest you to use DMA transfer (There are examples for that in Creator) although a bit complicate for the beginner.

   

 

   

Bob

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Bob_Marlowe
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Welcome in the forum

   

You only need a realistic sample rate to perform your filter. Nyquist is 2f, but I suggest 10 to 50f gives the best results.

   

250kHz * 20 is 5MHz sample rate which is a bit fast for the ADC. At 20kHz you would be fine off with a sample rate of 400kHz.

   

I would suggest you to use DMA transfer (There are examples for that in Creator) although a bit complicate for the beginner.

   

 

   

Bob

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odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted
        spgermany7, The KBA link you referfing to is about analog switching capacitor filter in PSoC1, which are not available in PSoC5. Bob Marlowe is referring you to the Digital Filter, which needs analog signal to be digitized first.   
Anonymous
Not applicable

Thank you for the reply. 

   

I was able to achieve till 35KHz. of sampling rate 384000.

   

Since adc del sigma has max sampling rate of 384000, we can't achieve more than it. 

   

Or is there a work around for this limitation.

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        At this sampling rate it might be worth using SAR_ADC. Each SAR_ADC can sample 12-bit @ 1 MHz. By interleaving data from two SAR_ADCs, combined sampling rate can be 2 MHz. 'Kabron' was able to get over the top rate limit by using external clock to the SAR_ADC, reaching ~2 MHz @ 7-bit, and combined speed over 3 MHz http://www.cypress.com/forum/psoc-5-device-programming/adc-sar-overclocking-technique At some rate the Filter can hit its limits, as it takes ~20 clocks to perform the MAC. P.S. ...and Bob Marlowe types faster.   
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My reply was shorter, I am a lousy typist 😉

   

 

   

Bob

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Bob_Marlowe
Level 10
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Set the PSoC clock to 72MHz and use the SAR ADC, you'll get up to 1Msps.

   

 

   

Bob

   

PS: BTW, where in Germany are you located? I live near Bremen.