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PSoC 5, 3 & 1 MCU

ShBa_282106
New Contributor II

Hi!

   

Can a positive tail pulse..amplitude no more than 5V and pulse duration maximum 50us (prf<= 1Mhz) be shaped to a gaussian near gaussian pulse using PSoC3?...Also like PSoC1 are the switched capacitor blocks available so that a simple CR-RC4 circuit can be realized?

   

Another thing...the block diagram of pulse oximeter on http://www.cypress.com/?rid=47829 shows an analog filter . I've not seen an analog filter in components of PSoC creator. How to find it?

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4 Replies
ETRO_SSN583
Esteemed Contributor

"Can a positive tail pulse..amplitude no more than 5V and pulse duration maximum 50us (prf<= 1Mhz) be shaped to a gaussian near gaussian pulse using PSoC3?..."

   

 

   

See comments below on last item

   


   

"Also like PSoC1 are the switched capacitor blocks available so that a simple CR-RC4 circuit can be realized?"

   

www.cypress.com/

   

and take a look at this - www.cypress.com/

   

 

   

"Another thing...the block diagram of pulse oximeter on http://www.cypress.com/?rid=47829 shows an analog filter . I've not seen an analog filter in components of PSoC creator. How to find it?"

   

 

   

PSOC 3 has a digital filter block and DAC that can be used for general purpose filter. However your sampling rate

   

requirement of at least 2 Mhz (1 Mhz Nyquist preferably 10 Mhz Nyquist)  cannot be done because there is

   

no fast SAR A/D to keep up wirth sampling rate. OpAmps could be used for filtering, but their GBW of 3 Mhz

   

too low to implement a meaningful repeatable filter at 1 Mhz.

   

 

   

Regards, Dana,

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Anonymous
Not applicable

Due to the central limit theorem, the Gaussian can be approximated by several runs of a very simple filter such as the moving average. The simple moving average corresponds to convolutionwith the constant B-spline ( a rectangular pulse ), and, for example, four iterations of a moving average yields a cubic B-spline as filter window which approximates the Gaussian quite well.

   

With pulse width of 50us, moving average filtering is doable, with 1mhz sampling  ADC and DMA

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Bob_Marlowe
Expert II

...and even the moving average can be done in hardware by using the UDBs programmed in Verilog and using a datapath could enforce the performance.

   

 

   

Bob

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ETRO_SSN583
Esteemed Contributor

The max sampling rate of Delsig, occuring at its lowest resolution, 8 bits, is 384K SPS,

   

16 bits at 48KSPS. PSOC 3  is limited to DelSig.

   

 

   

en.wikipedia.org/wiki/Gaussian_filter

   

 

   

The DFB block in PSOC 3/5 can be used to implement a FIR based Gaussian

   

approximation. Some design help can be found at -

   

www.mathworks.com/help/signal/examples/fir-gaussian-pulse-shaping-filter-design.html

   

 

   

Google "fir gaussian filter", there are a number of tools, some free, that can help

   

determining the coefficients for a FIR solution.

   

 

   

IIR approach - www.cwp.mines.edu/Meetings/Project06/cwp546.pdf

   

 

   

Regards, Dana.

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