3 Replies Latest reply on Apr 10, 2015 5:17 PM by dakn_263916

    Change filter coefficients of the DFB in runtime


      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!