This function applies IIR filter to ptrInput.

• BScale: B scale factor.
• AScale: A scale factor.
• ptrB: address of B coefficients (in program memory).
• ptrA: address of A coefficients (in program memory).
• FilterOrder: order of the filter + 1.
• ptrInput: address of input samples.
• InputLen: number of samples.
• ptrOutput: address of output samples. Output length is equal to Input length.
• Index: index of current sample.

Nothing.

const BUFFER_SIZE = 8;
const FILTER_ORDER = 6;
const COEFF_B: array[FILTER_ORDER+1] of word = (0x0548, 0x1FAE, 0x4F34, 0x699B, 0x4F34, 0x1FAE, 0x0548);
const COEFF_A: array[FILTER_ORDER+1] of word = (0x4000, 0xB3FE, 0x5389, 0xD4D8, 0x10DD, 0xFCB0, 0x0052);
const SCALE_B = 2;  
const SCALE_A = -1;  
var inext : word;                         // Input buffer index
    input : array[BUFFER_SIZE] of word; ydata; // Input buffer
    output : array[BUFFER_SIZE] of word; ydata; // Output buffer
...
var CurrentValue : word;
CurrentValue := IIR_Radix(SCALE_B,         
                         SCALE_A,         
                         word(@COEFF_B),  // b coefficients of the filter
                         word(@COEFF_A),  // a coefficients of the filter
                         FILTER_ORDER+1,  // Filter order + 1
                         word(@input),    // Input buffer
                         BUFFER_SIZE,     // Input buffer length
                         word(@output),   // Input buffer
                         inext);          // Current sample

Input and output samples must be in Y data space.