I am using the National Instruments (FPGA) 'Butterworth Filter' VI, to implement a 2nd order low pass filter.
The input and output signals are Fixed Point numbers with a signed integer word length of minus 4. I have been able to configure the cut-off frequency using the VI's dialog box, but I'd like to make this configurable at run time.The VI has an input called 'Scaled Coefficients', which takes a 3 element array of 32 bit signed integers.I therefore need to determine the value of these coefficients, but the documentation does not include information on how to calculate them.
I have noticed that the Real Time module includes a 'Butterworth Coefficients' VI, which outputs 5 doubles consisting of 3 forward coefficients and 2 reverse.
I am not sure whether i can use these values, or how to scale them to the integers for the FPGA VI?