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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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PSoC 5LP
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Thank you for information. Can you post sample project also?
odissey1
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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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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.