1701 and 1452 compressor and Crossover Formula calculation

Hello, I also use this module. The following three times can be calculated according to the formula you give. Now there is no formula for calculating the threshold and ratio. Is there a formula for this? Calculation formula of compressor and expander.

void SigmaDSP::compressorPeak(uint16_t startMemoryAddress, compressor_t &compressor)
{
uint8_t i;
uint8_t count;

float curve[33];
float x[33];
float y[33];
float delta = 0.00;
float coeff = 0.00;

float dbps = 0.00;
float hold_par = 0.00;
float decay_par = 0.00;
float postgain_par = 0.00;

linspace(-90, 6, 33, x);

count = 0;

coeff = 1/compressor.ratio;
for(i = 0; i < 33; i++) // This algorithm creates the curve with 1 1 1 1 1 1 1 0.9 0.8 0.72 0.64 and so on coefficients
{
if(x[i] >= compressor.threshold)
{
count++;
if(count == 1)
delta = x[i]*coeff-x[i]*1;
y[i] = (x[i] * coeff)-delta;
}
else
y[i] = x[i] * 1;
}

for(i = 0; i < 33; i++) // Coefficients of the curve calculation
curve[i] = (pow(10, y[i]/20)) / (pow(10, x[i]/20)); // Coefficients are the ratio between the linearized values of vect. y and x

// Create buffer to store converted data
uint8_t storeData[5];

// Parameter load into Sigma DSP
for(i = 0; i < 33; i++)
{
floatToFixed(curve[i], storeData);
safeload_writeRegister(startMemoryAddress++, storeData, false);
}

I now have this calculation formula, but it is wrong, because I use the compressor ratio and expander ratio. The calculated array and software are incorrect. How do I calculate this?

I want to control the compressor, but I find many slope types. I find that Butterworth12 has the same parameter values as the second-order filter. I have this formula.

// Butterworth lowpass
case parameters::filterType::butterworthLowpass:
alpha = sin(w0) / 2.0 * 1/sqrt(2);
a0 = 1 + alpha;
a1 = -2*cos(w0);
a2 = 1 - alpha;
b0 = (1 - cos(w0)) * gainLinear / 2;
b1 = (1 - cos(w0)) * gainLinear;
b2 = (1 - cos(w0)) * gainLinear / 2;
break;

// Butterworth highpass
case parameters::filterType::butterworthHighpass:
alpha = sin(w0) / 2.0 * 1/sqrt(2);
a0 = 1 + alpha;
a1 = -2*cos(w0);
a2 = 1 - alpha;
b0 = (1 + cos(w0)) * gainLinear / 2;
b1 = -(1 + cos(w0)) * gainLinear;
b2 = (1 + cos(w0)) * gainLinear / 2;
break;

// Bessel lowpass
case parameters::filterType::besselLowpass:
alpha = sin(w0) / 2.0 * 1/sqrt(3) ;
a0 = 1 + alpha;
a1 = -2*cos(w0);
a2 = 1 - alpha;
b0 = (1 - cos(w0)) * gainLinear / 2;
b1 = (1 - cos(w0)) * gainLinear;
b2 = (1 - cos(w0)) * gainLinear / 2;
break;

// Bessel highpass
case parameters::filterType::besselHighpass:
alpha = sin(w0) / 2.0 * 1/sqrt(3) ;
a0 = 1 + alpha;
a1 = -2*cos(w0);
a2 = 1 - alpha;
b0 = (1 + cos(w0)) * gainLinear / 2;
b1 = -(1 + cos(w0)) * gainLinear;
b2 = (1 + cos(w0)) * gainLinear / 2;
break;
}

But if the slope exceeds 12, it will not be calculated. Where can this formula be?

software

4.7

1701 1452