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Digital notch filter function with specific external storage, so it can be used in multiple calls.

Syntax

real filter_notch_st (real val, real omega, real valQ, real storage[2], real period, i32 flagInit)

val

Is the value (or a generic mathematical expression) to be filtered

omega

Value of the cut filter omega in radians per second (omega = 2 * K_PI * cut frequency (Hz)). It can be a generic mathematical expression

valQ

Value of the filter Q coefficient (Q must be >= 0.75). Can be a generic mathematical expression

storage

Storage variable for mathematical processing of the filter function

period

Sampling interval, if <= 0 si is assumed

flagInit

Variable for filter initialization request; imposing a value different than 0 will reset the filter and the flagInit variable will be written to 0. The first time the function is called this variable must have a value different than 0

Result

Returns the filtered value

Validity

Rule

Note

Automatic omega limitation: (omega_max = 0.15 / si * 2 * K_PI) -> i.e. no more than 15% of omega value corresponding to rule sampling time.

(e.g. if Freq = 200Hz -> filter cut frequency <= 30 Hz)

The parameters are as for filter_notch(), but in addition it allows you to specify a storage variable used for mathematical processing of the filter function.

In this way, filters can also be used with multiple calls (e.g., within for loops).

 

  

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