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PSoC 5, 3 & 1

WoKi_264666
New Contributor II

Any time before there was a question on the forum: Can I change  the filter constants in runtime ?
My answer is: Yes you can.

   

Here is a code snippet that complains, how it works.

   

void LoadFilter (uint8 fltr)// fltr is the pointer to the dedicated parameter block

   

{ // Put DFB RAM on the bus :

   

    Filter_RAM_DIR_REG = Filter_RAM_DIR_BUS;

   

if (fltr == 1)

   

        cymemcpy(Filter_DB_RAM,Filter100_data_b, Filter_DB_RAM_SIZE);

   

else if (fltr == 2)

   

        cymemcpy(Filter_DB_RAM,Filter200_data_b, Filter_DB_RAM_SIZE);

   

else if (fltr == 3)

   

        cymemcpy(Filter_DB_RAM,Filter400_data_b, Filter_DB_RAM_SIZE);

   

else if (fltr == 4)

   

        cymemcpy(Filter_DB_RAM,FilterTP2800_data_b, Filter_DB_RAM_SIZE);

   

// Take DFB RAM off the bus :

   

Filter_RAM_DIR_REG = Filter_RAM_DIR_DFB;

   

}

   

    

   

The Filter_data you can compute with the embedded filter wizard. After setting your parameters 

   

in the Filter Block, build the application an then read out the file Filter:Ram_Data.c :

   

const uint8 CYCODE Filter_data_b[] = 

   

{

   

    0x14, 0xD0, 0x01, 0x00, 0x28, 0xA0, 0x03, 0x00,...

   


And if you want to change the filter structure ( FIR --> IIR) you have to exchange in the same way the following matrix:

   


const uint8 CYCODE Filter_control[] = 

   

{

   

    0x20, 0x13, 0x00, 0x25, 0x61, 0x17, 0x80, 0x26,....

   


Don't know why all filter coefficients are located in Filter_data_b, even when you use filter stage A... 

   


Good luck!

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3 Replies
odissey1
Honored Contributor II

 Thank you for information. Can you post sample project  also?

   

odissey1

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WoKi_264666
New Contributor II

Only a "big" program is available here, that includes the focused lines. 

   

Please note: compiles with PSoC Creator 2.2, because I used a CY8CKit-014 with CY5588AXI.060-ES1.

   

Interesting for the problem are:

   

main.c      line 723 ...

   

filters.c     complete

   

main.h      line 13 ...

   

 

   

Have fun!

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ETRO_SSN583
Esteemed Contributor

On location of coefficients, from tech support -

   

 

   

    

   

          

   

1. "Why, when doing a chan a and chan b filter, 64 taps each, does all the filter data show up in Filter_data_b[], none in Filter_data_a[] ?"

   

 

   

The DFB has 2 data RAMs. One of the 2 RAM blocks is used to store the filter co-efficients of both the channels. And the other RAM block is used to store the intermediate data or the incoming samples.

   

That is the reason why both the channels' co-efficients are stored in the data RAM B.

   

 

   

2. "Why are the arrays, both, defined as 32 coefficients ? Is that due to symmetry of response, so you only need 1/2 the coefficients ?"

   

 

   

Yes.

   

 

   

3. For the BiQuad also, the data RAM B will hold the co-efficients.

   

 

   

Regards, Dana.

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