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PSoC5lp Band Pass Filter | Cypress Semiconductor

PSoC5lp Band Pass Filter

Summary: 6 Replies, Latest post by Bob Marlowe on 27 Oct 2016 07:48 AM PDT
Verified Answers: 3
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spgermany7_1996721's picture
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2 posts

Hey guys,

I just came across this article

http://www.cypress.com/knowledge-base-article/frequency-limits-low-pass-...

 

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.

 

user_1377889's picture
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9606 posts

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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user_342122993's picture
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582 posts

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.

spgermany7_1996721's picture
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2 posts

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.

 

user_342122993's picture
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582 posts

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-overclock...

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.

user_1377889's picture
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9606 posts

My reply was shorter, I am a lousy typist ;-)

 

Bob

user_1377889's picture
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9606 posts

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.

 

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