Hi,
I use the 'Butterworth Filter Express' VI in my LabVIEW FPGA code. This VI is both configured via some dialog box options, and by cabling some scaling coefficients to its inputs. I calculate the filtering coefficients in the RT side using the 'Butterworth Coefficients' VI, I pass these coeffs to the FPGA and wire them to the 'Butterworth Filter Express' VI.
Among the dialog box options, there are two options that deal directly with the cutoff frequency:
- Cutoff frequency
- Expected sample rate
However, I already specify these properties when I calculate the filtering coeffs in the RT. So, my question is simple:
Since the sample rate and cutoff frequency are specified when calculating the filtering coeffs, are the cutoff frequency and expected sample rate in the FPGA side (dialog box) ignored when you wire some values to the filtering coeffs inputs?
To my understanding the parameters in the dialog box of the FPGA side are taken into account when we dont wire any value to the scaling coeffs input, thus giving a constant cutoff frequency. However, if the cutoff frequency is calculated in the RT as scaling parameters (thus we can vary the cutoff freq), both Cutoff frequency and Expected sample rate of the dialog box are ignored.
Am I right?