Multiple filter point by point implementation

[yamelbio]

Hello, I would like to implement multiple digital filters "point by point", as many as the user needs, if he selects, for example, 3 filters, since the input value is filtered 3 times with different specifications.

Currently I have a program that allows the user to filter once with the specifications they want, but I don't know how to make it filter N times "point by point".

[altenbach · Accepted solution]

ptbypt filters are reentrant, so each instance has it's own internal data. You could just chain them up and skip some with case structures. What is the max number of passes the user needs? Maybe you can reduce the multiple filter parameters to a new set that can do it in one filter pass?

[yamelbio]

I just realize of something: filters eliminate some high, low or specific frecquencys, I dont need 3 or 4 filters if I can select the bandwidth and...10 order!

maybe I can implement some Notch filter after and give the option of activate it or not...

in the same way the option to eliminate DC component, there is no need of more.

In case of user wants to add bandwidths like: 20-50Hz + 100-150Hz, for ECG waves (for example), I will have to implement parallel structures, but that is not hard...

Ok thank you very much!