RSI IIR Filter Problem

abrady · Jun 25th 2015

Hi,

I'm running KSS V5.5.14 and RSI V2.1.1, and I'm having an issue with the st_iirfilter command.

Here is the code I'm using to test it. It just generates an amplitude 1, freq 1 sine wave and runs it through a 2nd order low pass butterworth filter with cutoff frequency 2Hz.

Code

Def filter_source()


INI


ptp $pos_act


;Signal
ret=st_source(hsrc,0,rsiunit_no)
ret=st_setparam(hsrc,1,1) ;sine
ret=st_setparam(hsrc,2,0) ; no offset
ret=st_setparam(hsrc,3,1) ;amplitude 1
ret=st_setparam(hsrc,4,1) ;frequency 1


;Filter: low pass, Butterworth, order2, cutoff freq=2Hz
ret=st_iirfilter(hfilter,0,hsrc,1,0,1,2,2)

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When run it I get the error "RSI: Error in function <ST_IIRFILTER>"
Can someone spot the problem? Thanks.

**panic mode** · Jun 26th 2015

where did you get info about IIR filter in RSI? this seem to be implemented in RSI3.x but I cannot find any hint of it in earlier versions.

abrady · Jun 26th 2015

I found it in the document rsiCommands V2.3:

https://www.dropbox.com/sh/y9g…c5LwG6Mk1dfHGUWw_Pxa?dl=0

It seems to recognize the function since the error message is "RSI: Error in function <ST_IIRFILTER>". I also checked the log file which shows that the iirfilter object was created and then immediately deleted. Strange. I'll post that in a few.

**panic mode** · Jun 26th 2015

message you get tells you that there is an error with calling ST_IIRFILTER function:

Code

ret=st_iirfilter(hfilter,0,hsrc,1,0,1,2,2)

which sets IIR parameters:
OBJID = hfilter, ; ID of the created RSI object
CONTID = 0, ; ID of container of the new object
ID1 = hsrc, ;ID of the object to link to input 1.
IDX1 = 1, ; Output index of ID1 to link to input 1
type = 0, ; using Lowpass type filer
NAME = 1, ; Butterworth
ORDER = 2, ; 6th order filter
cutoffFREQ = 2; Cuttoff is 2kHz

According to function definition:

Code

GLOBAL DEFFCT RSIERR ST_IIRFILTER(OBJID:OUT,CONTID:IN,ID1:IN,IDX1:IN,type:IN,NAME:IN,ORDER:IN,cutoffFREQ:IN)




Parameters:
OUT OBJID (INT): ID of the created RSI object
IN CONTID (INT): ID of container for the new object
IN ID1 (INT): ID of the object to link to input 1
IN IDX1 (INT): Output index of ID1 to link to input 1
IN type (INT): Type of filter
-> 0: Lowpass
-> 1: Highpass
IN NAME (INT):
-> 0: Bessel
-> 1: Butterworth
-> 2: Tschebyscheff with ripple 0.5 db
-> 3: Tschebyscheff with ripple 1 db
-> 4: Tschebyscheff with ripple 2 db
-> 5: Tschebyscheff with ripple 3 db
IN ORDER (INT) -> 0: 2 order
-> 1: 4 order
-> 2: 6 order
-> 3: 8 order
-> 4: 10 order
IN CUTFREQ (REAL):Cutoff frequency in [Hz]

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I would focus on parameters 2-4...

RSI IIR Filter Problem

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